Penetrating Head Trauma

Background

Traumatic brain injury (TBI) is the fourth leading cause of death in the United States and is the leading cause of death in persons aged 1-44 years. Approximately 2 million traumatic brain injuries occur each year, and an approximate $25 billion per year is spent in social and medical management of people with such injuries.
Analysis of the trauma literature has shown that 50% of all trauma deaths are secondary to traumatic brain injury (TBI), and gunshot wounds to the head caused 35% of these. The current increase in firearm-related violence and subsequent increase in penetrating head injury remains of concern to neurosurgeons in particular and to the community as a whole.
The CT scan below is of a patient after a gunshot wound to the brain.

A young man arrived in the emergency department after experiencing a gunshot wound to the brain. The entrance was on the left occipital region. A CT scan shows the skull fracture and a large underlying cerebral contusion. The patient was taken to the operating room for debridement of the wound and skull fracture, with repair of the dura mater. He was discharged in good neurological condition, with a significant visual field defect. 

The definition of a penetrating head trauma is a wound in which a projectile breaches the cranium but does not exit it. Despite the prevalence of these injuries, the morbidity and mortality of penetrating head injury remains high. Improvements in the understanding of the mechanisms of injury and aggressive medical and surgical management of patients with these injuries may lead to improved outcomes.
This chapter focuses on the pathophysiology of both primary and secondary mechanisms of injury, describes the treatment of patients from presentation to discharge, and concludes with a discussion of possible complications and patient outcome. For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education article Brain Infection.

History of the Procedure

The earliest reported series of head injuries and their management appears in the Edwin Smith papyrus around 1700 BC, reporting 4 depressed skull fractures treated by the Egyptians by leaving the wound unbandaged, providing free drainage of the intracranial cavity, and anointing the scalp wound with grease. Hippocrates (460-357 BC) performed trephination for contusions, fissure fractures, and skull indentations. Galen's experience in 130-210 AD treating wounded gladiators led to recognition of a correlation between the side of injury and the side of motor loss.
During the Dark Ages, little progress was made in the surgical management of head wounds and medicine continued to hold a pessimistic view of head wounds with torn dura mater. In the 17th century, Richard Wiseman provided a better understanding of surgical management of penetrating brain injuries; he recommended the evacuation of subdural hematomas and the extraction of bone fragments. In his experience, deep wounds had a much worse prognosis than superficial ones.
Major advances in the management of penetrating craniocerebral injuries in the mid-19th century were related to the work of Louis Pasteur (1867), Robert Koch in bacteriology (1876), and Joseph Lister in asepsis (1867). Such advances dramatically reduced the incidence of local and systemic infections, as well as mortality.

Problem

In the past 20 years, a dramatic increase in the incidence of penetrating injuries to the brain has occurred. Gunshot wounds to the head have become the leading or second leading cause of head injury in many cities in the United States. These injuries are devastating to the patient, family, and society.
Siccardi et al (1991) prospectively studied a series of 314 patients with craniocerebral missile wounds and found that 73% of the victims died at the scene, 12% died within 3 hours of injury, and 7% died later, yielding a total mortality of 92% in his series.In another study, gunshot wounds were responsible for at least 14% of the head injury-related deaths from 1979-1986.
Age-adjusted death rates for injury by firearms have increased nearly every year since 1985. A study using multiple logistic regressions found that injury from firearms greatly increases the probability of death and that the victim of a gunshot wound to the head is approximately 35 times more likely to die than is a patient with a comparable nonpenetrating brain injury.

Epidemiology

Frequency

A National Institutes of Health survey estimates that in the United States, 1.9 million persons annually experience a skull fracture or intracranial injury, and, of these cases, one-half have a suboptimal outcome. In 1992, firearms accounted for the largest proportion of deaths from traumatic brain injury in the United States, and gunshot wounds were the most common cause of mortality in African Americans.

Etiology

Penetrating head injuries can be the result of numerous intentional or unintentional events, including missile wounds, stab wounds, and motor vehicle or occupational accidents (nails, screwdrivers).
Stab wounds to the cranium are typically caused by a weapon with a small impact area and wielded at low velocity. The most common wound is a knife injury, although bizarre craniocerebral-perforating injuries have been reported that were caused by nails, metal poles, ice picks, keys, pencils, chopsticks, and power drills.

Pathophysiology

The pathological consequences of penetrating head wounds depend on the circumstances of the injury, including the properties of the weapon or missile, the energy of the impact, and the location and characteristics of the intracranial trajectory. Following the primary injury or impact, secondary injuries may develop. Secondary injury mechanisms are defined as pathological processes that occur after the time of the injury and adversely affect the ability of the brain to recover from the primary insult. A biochemical cascade begins when a mechanical force disrupts the normal cell integrity, producing the release of numerous enzymes, phospholipids, excitatory neurotransmitters (glutamate), Ca, and free oxygen radicals that propagate further cell damage.

Missile wounds

Missiles range from low-velocity bullets used in handguns, as shown in the image below, or shotguns to high-velocity metal-jacket bullets fired from military weapons.Low-velocity civilian missile wounds occur from air rifle projectiles, nail guns used in construction devices, stun guns used for animal slaughter, and shrapnel produced during explosions. Bullets can cause damage to brain parenchyma through 3 mechanisms: (1) laceration and crushing, (2) cavitation, and (3) shock waves. The injury may range from a depressed fracture of the skull resulting in a focal hemorrhage to devastating diffuse damage to the brain.

A 65-year-old man experienced a gunshot wound to the right frontoparietal region. A CT scan shows that the bullet crossed the midline, lacerated the superior longitudinal sinus, and produced a large midline subdural hematoma. The patient presented with a Glasgow Coma Scale (GCS) score of 4 and died. 

As stated previously, a wound in which the projectile breaches the cranium but does not exit is described technically as penetrating, and an injury in which the projectile passes entirely though the head, leaving both entrance and exit wounds, is described as perforating. This distinction has some prognostic implications. In a series of missile-related head injuries during the Iran-Iraq war, a poor postsurgical outcome occurred in 50% of patients treated for perforating wounds, as compared with only 20% of those with penetrating wounds.
In missile wounds, the amount of damage to the brain depends on numerous factors including (1) the kinetic energy imparted, (2) the trajectory of the missile and bone fragments through the brain, (3) intracranial pressure (ICP) changes at the moment of impact, and (4) secondary mechanisms of injury. The kinetic energy is calculated employing the formula 1/2mv², where m is the bullet mass and v is the impact velocity.
At the time of impact, injury is related to (1) the direct crush injury produced by the missile, (2) the cavitation produced by the centrifugal effects of the missile on the parenchyma, and (3) the shock waves that cause a stretch injury. As a projectile passes through the head, tissue is destroyed and is either ejected out of the entrance or exit wounds or compressed into the walls of the missile tract. This creates both a permanent cavity that is 3-4 times larger than the missile diameter and a pulsating temporary cavity that expands outward. The temporary cavity can be as much as 30 times larger than the missile diameter and causes injury to structures a considerable distance from the actual missile tract.

Stab wounds

This group of wounds, example depicted below, represents a smaller fraction of penetrating head injuries. The causes may be from knives, nails, spikes, forks, scissors, and other assorted objects. Penetrations most commonly occur in the thin bones of the skull, especially in the orbital surfaces and the squamous portion of the temporal bone. The mechanisms of neuronal and vascular injury caused by cranial stab wounds may differ from those caused by other types of head trauma. Unlike missile injuries, no concentric zone of coagulative necrosis caused by dissipated energy is present. Unlike motor vehicle accidents, no diffuse shearing injury to the brain occurs

A CT scan of a young female who presented to the emergency department with a stab wound to the head produced by a large knife shows the extent of intracranial damage, which affects midline structures.

Unless an associated hematoma or infarct is present, cerebral damage caused by stabbing is largely restricted to the wound tract. A narrow elongated defect, or so-called slot fracture, sometimes is produced by a stab wound and is diagnostic when identified. However, in some cases in which skull penetration is proven, no radiological abnormality can be identified. In a series of stab wounds, de Villiers (1975) reported a mortality of 17%, mostly related to vascular injury and massive intracerebral hematomas.
Stab wounds to the temporal fossa are more likely to result in major neurological deficits because of the thinness of the temporal squama and the shorter distance to the deep brain stem and vascular structures. Patients in whom the penetrating object is left in place have a significantly lower mortality than those in whom the objects are inserted and then removed (26% versus 11% respectively).

Skull perforations and fractures

The local variations in thickness and strength of the skull and the angle of the impact determine the severity of the fracture and injury to the brain, as shown below. Impacts striking the skull at nearly perpendicular angles may cause bone fragments to travel along the same trajectory as the penetrating object, to shatter the skull in an irregular pattern, or to produce linear fractures that radiate away from the entry defect. Grazing or tangential impacts produce complex single defects with both internal and external beveling of the skull, with varied degrees of brain damage.

Lateral skull x-ray film of a patient who presented with a severe intracranial injury produced by a golf club.

The patient presented to the emergency department with a golf club in his head. The club was removed in the operating room. 

Presentation

The clinical condition of the patient depends mainly on the mechanism (velocity, kinetic energy), anatomical location of the lesions, and associated injuries.

Traumatic intracranial hematomas

These can occur alone or in combination and constitute a common and treatable source of morbidity and mortality resulting from brain shift, brain swelling, cerebral ischemia, and elevated ICP. Patients present with the signs and symptoms of an expanding intracranial mass, and the clinical course varies according to the location and rate of accumulation of the hematoma. The classic clinical picture of epidural hematomas is described as involving a lucid interval following the injury; the patient is stunned by the blow, recovers consciousness, and lapses into unconsciousness as the clot expands.

Epidural hematomas

Most traumatic epidural hematomas become rapidly symptomatic with progression to coma. Acute subdural hematoma occurs in association with high rates of acceleration and deceleration of the head that takes place at the time of trauma. This remains one of the most lethal of all head injuries because the impact causing acute subdural hematoma commonly results in associated severe parenchymal brain injuries.

Intracerebral hematomas

These result from direct rupture of small vessels within the parenchyma at the moment of impact. Patients typically present with a focal neurological deficit related to the location of the hematoma or with signs of mass effect and increased ICP. The occurrence of delayed traumatic intracerebral hematomas is well documented in the literature.

Delayed intracerebral hematomas

The time interval for the development of delayed intracerebral hematomas ranges from hours to days. Although these lesions may develop in areas of previously demonstrated contusion, they frequently occur in the presence of completely normal results on the initial computed tomography (CT) scan. Patients with this diagnosis typically meet the following criteria: (1) a definite history of trauma, (2) an asymptomatic interval, and (3) an apoplectic event with sudden clinical deterioration.

Contusions

These consist of areas of perivascular hemorrhage about small blood vessels and necrotic brain. Typically, they assume a wedgelike shape, extending through the cortex to the white matter. When the pia-arachnoid layer is torn, the injury is termed a cerebral laceration. Clinically, cerebral contusions serve as niduses for delayed hemorrhage and brain swelling, which can cause clinical deterioration and secondary brain injury.

Traumatic subarachnoid hemorrhage

This type of hemorrhage usually is a result of various forces that produce stress sufficient to damage superficial vascular structures running in the subarachnoid space. Traumatic subarachnoid hemorrhage may predispose to cerebral vasospasm and diminished cerebral blood flow, thereby increasing morbidity and mortality as a result of secondary ischemic damage.

Diffuse axonal injury or shearing injury

This has become recognized as one of the most important forms of primary injury to the brain. In the most extreme form, patients present with immediate prolonged unconsciousness from the moment of injury and subsequently remain vegetative or severely impaired.

Indications

A critical factor in early treatment decisions and in long-term outcome after penetrating head injuries is the patient's initial level of consciousness. Although many methods of defining level of consciousness exist, the most widely used measure is the Glasgow Coma Scale (GCS) introduced by Teasdale and Jennett in 1974.
Table. Glasgow Coma Scale

Points	Eye Opening	Best Verbal	Best Motor
6	…	…	Follows commands
5	…	Appropriate	Localizes pain
4	Spontaneous	Inappropriate	Withdraws to pain
3	In response to voice	Moaning	Flexion (decorticate)
2	In response to pain	Incomprehensible	Extension (decerebrate)
1	None	None	None

The level of consciousness can be lowered independent of head injury for numerous reasons, including shock, hypoxia, hypothermia, alcohol intoxication, postictal state, and administration of sedatives or narcotics. Therefore, a more reliable assessment of severity and, thus a more meaningful predictor of outcome, is provided by the postresuscitation GCS score (hereafter referred to as GCS), which generally refers to the best level obtained within the first 6-8 hours of injury following nonsurgical resuscitation. This allows patients to be categorized into 3 levels, as follows:

• Minor or mild injury includes those patients with an initial level of 13-15.
• Moderate injury includes patients with a score of 9-12.
• Severe injury refers to a postresuscitation level of 3-8 or a subsequent deterioration to 8 or less.

Patients with severe head injury typically fulfill the criteria for coma, have the highest incidence of intracranial mass lesions, and require intensive medical and, often, surgical intervention.

Relevant Anatomy

Penetrating objects to the cranium must traverse through the scalp, through the skull bones, and through the dura mater before reaching the brain.
The scalp consist of 5 different anatomical layers that include the skin (S); the subcutaneous tissue (C); the galea aponeurotica (A), which is continuous with the musculoaponeurotic system of the frontalis, occipitalis, and superficial temporal fascia; underlying loose areolar tissue (L); and the skull periosteum (P).
The subcutaneous layer possesses a rich vascular supply that contains an abundant communication of vessels that can result in a significant blood loss when the scalp is lacerated. The relatively poor fixation of the galea to the underlying periosteum of the skull provides little resistance to shear injuries that can result in large scalp flaps or so-called scalping injuries. This layer also provides little resistance to hematomas or abscess formation, and extensive fluid collections related to the scalp tend to accumulate in the subgaleal plane.
The bones of the calvaria have 3 distinct layers in the adult—the hard internal and external tables and the cancellous middle layer, or diploë. Although the average thickness is approximately 5 mm, the thickest area is usually the occipital bone and the thinnest is the temporal bone. The calvaria is covered by periosteum on both the outer and inner surfaces. On the inner surface, it fuses with the dura to become the outer layer of the dura.
Aesthetically, the frontal bone is the most important because only a small portion of the frontal bone is covered by hair. In addition, it forms the roof and portions of the medial and lateral walls of the orbit. Displaced frontal fractures therefore may cause significant deformities, exophthalmus, or enophthalmos. The frontal bone also contains the frontal sinuses, which are paired cavities located between the inner and outer lamellae of the frontal bone. The lesser thickness of the anterior wall of the frontal sinus makes this area more susceptible to fracture than the adjacent tempora-orbital areas.
The dura mater or pachymeninx is the thickest and most superficial meninx. It consists of 2 layers—a superficial layer that fuses with the periosteum and a deeper layer. In the same region between both layers, large venous compartments or sinuses are present. A laceration through these structures can produce significant blood loss or be responsible for producing epidural or subdural hematomas.

 

 

Choroid Plexus Papilloma

Background

Choroid plexus papillomas (CPPs) are benign neoplasms of the choroid plexus, a structure made from tufts of villi within the ventricular system that produces cerebrospinal fluid (CSF). CPPs are commonly observed in the lateral ventricles of children, but they can be encountered in adults. While the vast majority of these neoplasms are benign, a small percentage can be malignant.
An image depicting a choroid plexus papilloma can be seen below.

Imaging appearance of a fourth ventricular choroid plexus papilloma (CPP).

History of the Procedure

Guerard described the first CPP (in a 3-year-old girl) in 1832, and Perthes described the first successful surgical removal in 1919.

Problem

The choroid plexus is a neuroepithelial-lined papillary projection of the ventricular ependyma. The papillae consist of cores of fibrovascular tissue lined by low-cuboidal neuroepithelial cells. While benign cystic lesions of the choroid plexus are not uncommon, neoplasms are rare. Although most choroid plexus neoplasms are benign, they can become symptomatic by obstructing CSF flow, eventually leading to generalized increased intracranial pressure or mass effect.

Epidemiology

Frequency

CPPs are rare, comprising less than 1% of brain tumors in patients of all ages. However, CPPs most often occur in children and constitute up to 3% of childhood intracranial neoplasms with a predilection for younger ages. CPPs comprise 4-6% of the intracranial neoplasms in children younger than 2 years and 12-13% of intracranial neoplasms in children younger than 1 year.
CPPs have been associated with von Hippel-Lindau syndrome and Li-Fraumeni syndrome.
The frequency of CPPs in children is similar in China (1.5%) and France (2.3%)
The male-to-female incidence ratio of CPP is 2.8:1.
No distribution by race has been described.

Etiology

CPPs arise from the single layer of cuboidal epithelial cells lining the papillae of the choroid plexus. The choroid plexus is associated with the ventricular lining of the body, trigone, and inferior horn of the lateral ventricles; the foramen of Monro; the roof of the third ventricle; and the posterior portion of the roof of the fourth ventricle. The typical locations of normal choroid plexus correspond to the most common locations for a CPP to occur.
A recent study points to the role of a transmembrane receptor protein (Notch3) in the pathogenesis of human choroid plexus tumors. The Notch pathway helps regulate development of the mammalian nervous system, and activation of the Notch pathway has been increasingly recognized in human cancers. Notch3 is expressed in ventricular zone progenitor cells in the fetal brain and, when activated, can function as an oncogene.
CPPs are associated with the Li-Fraumeni cancer syndrome (an autosomal dominant syndrome characterized by a germline mutation in the TP53 gene) and the Aicardi syndrome (a rare X-linked dominant condition observed in females, characterized by visual impairment, developmental delay, and seizures).
Both somatic and germline abnormalities that involve multiple genetic loci have been associated with the development of choroid plexus tumors. Recent genomic hybridization data shows that choroid plexus papillomas and choroid plexus carcinomas have characteristic chromosomal additions and deletions, which suggests that the genetic basis for these tumors is distinct
The polyoma viruses SV40, JC, and BK have also been implicated in the development of choroid plexus tumors. Choroid plexus tumors have been induced experimentally in transgenic mice using the polyomavirus common gene product, T antigen. The mechanism is thought to involve the binding of T antigen with both pRb and p53 tumor suppressor proteins, as these complexes have been identified in humans with choroid plexus tumors.Research is ongoing to further elucidate the relationship between polyoma viruses and human CNS tumors.
Recent research has also demonstrated differential expression of several genes in choroid papilloma tumor cells using DNA microarray techniques on cells from 7 choroid plexus papillomas. Among the abnormalities identified was up-regulation of the TWIST-1 transcription factor, which was shown to promote proliferation and in vitro invasion. TWIST-1 is involved in the p53 tumor suppressor pathway as an inhibitor.

Pathophysiology

Symptoms from choroid plexus tumors generally result from secretion of CSF by tumor cells, leading to an increased amount of fluid and, eventually, to hydrocephalus. Not infrequently, the tumor itself can cause mass effect, with symptoms depending on tumor location. In either case, eventual progression and increased intracranial pressure can occur. Cases of hydrocephalus occasionally do not resolve with surgery, possibly because of derangement of reabsorption mechanisms or blockage at other sites in the ventricular system.

Presentation

Patients usually present with the following signs of increased intracranial pressure: headache, nausea and vomiting, drowsiness, ocular or gaze palsies (cranial nerves [CN] III and VI), papilledema, visual disturbances, and, eventually, blindness.
Infants, especially those with a tumor located in the third ventricle, can present with hydrocephalus or macrocephalus, as well as with associated increased intracranial pressure.
Unusual presentations include trochlear palsies (CN IV), psychosis, or occasionally, seizures.

Indications

As CPPs grow, they eventually obstruct the flow of CSF. Once the intracranial space can no longer compensate for the increase in pressure, a tension-obstruction type of hydrocephalus develops. Persistently increased intracranial pressure is not compatible with life. The pressure is alleviated by resection of the tumor or a ventricular shunting procedure.

Relevant Anatomy

Because the choroid plexus is located within the ventricles, the CPP can expand into a space-occupying lesion that may not cause symptoms until either the flow of CSF is blocked or the papilloma becomes large enough to press against the ventricular walls and, subsequently, the brain parenchyma.
These tumors most often occur in the lateral ventricles in children and in the fourth ventricle or cerebellopontine angle (CPA) of adults. Bilateral CPA choroid plexus papillomas have also been reported in the setting of neurofibromatosis Type 2 Rarely, CPPs can also be found in the third ventricle. Other unusual or rare sites include the sella and primary intraparenchymal sites.Occasionally, CPPs show extensive calcification or even ossification or may lack their usual radiographic contrast enhancement.
In some instances, choroid plexus can be found in the cerebellopontine angle, where it has escaped the ventricle via the lateral foramen of Luschka. From this unusual placement of the choroid, or from exophytic growth of the papilloma through the foramen of Luschka, CPPs sometimes manifest in the cerebellopontine angle.The appearance of CPPs in unusual sites most frequently occurs in the setting of von Hippel-Lindau syndrome.Grossly, these tumors are tan and lobulated. They fill the ventricles and compress the walls; when they are benign, they do not generally invade brain parenchyma.

Contraindications

Contraindications to surgical correction of CPP are based on the patient's comorbidities and his or her ability to tolerate surgery. However, watchful waiting is inappropriate in most cases. As choroid plexus tumors grow, the resulting hydrocephalus and other complications usually result in greater morbidity than occurs if tumors are removed when they are first discovered and smaller.

 

Neurofibromatosis

Historically, descriptions of individuals thought now to have neurofibromatosis (NF) have been found in manuscripts dating back to 1000 AD. Von Recklinghausen coined the term 'neurofibroma' in 1881 to describe a benign tumour arising from the peripheral nerve sheath. Consequently, type 1 neurofibromatosis (NF1) is also known as Von Recklinghausen's disease.

Introduction

It is a genetic disorder causing lesions in the skin, nervous system and skeleton. There are two main types of neurofibromatosis (NF).

• Type 1 is the more common form and caused by a defect in the gene, NF1, situated at chromosome 17q11.2. Neurofibromin, the gene product, is a ubiquitous nervous system protein and is believed to act as a tumour suppressor.
  • Loss of neurofibromin leads to an increased risk of developing benign and malignant tumours but effects of a mutation are highly variable between sufferers and can appear at any age due to a variety of mutations, differing penetration and mosaicism.
  • Watson's syndrome is the only subtype of NF1 to have a uniform phenotype in families and is characterised by pulmonary stenosis, cognitive impairment, café au lait patches and few cutaneous neurofibromas.
• Type 2 is a central form with CNS tumours rather than skin lesions. There are inherited schwannomas (vestibular tumours), typically bilateral, but also meningiomas and ependymomas. It may be considered to be a type of schwannomatosis rather than NF. The implicated mutation is on chromosome 22 at gene locus 22q12.2.

There are several other rarer types including type 3 (NF3), type 4 (NF4) and neurofibromatosis-Noonan syndrome (NFNS), (not to be confused with Noonan's syndrome).

Epidemiology

Both type 1 and 2 of neurofibromatosis (NF) are inherited as autosomal dominant conditions but, for both types, there is no family history in about 50%, reflecting the incidence of new mutations.

• The birth incidence of type 1 is given as 1 in 2,500-3,000 but may be slightly higher because of failure to diagnose milder cases.
• NF type 2 has a prevalence of about 1 in 25,000.

The sex ratio is equal. It appears to be more common in white races.

Presentation

Diagnostic criteria for type 1 neurofibromatosis (NF1)

There are diagnostic criteria for NF1 that require at least 2 of 7 criteria. Some of these do not appear until later childhood or adolescence, and so confirmation of the diagnosis may be delayed and children should be followed up.

• At least six café au lait spots or hyperpigmented macules. They must be at least 5 mm wide in children younger than 10 years and 15 mm in adults.
• Axillary or inguinal freckles.
• Two or more typical neurofibromas or one plexiform neurofibroma.
• Optic nerve glioma.
• Two or more iris hamartomas. They are called Lisch nodules and are seen by slit-lamp examination.
• Sphenoid dysplasia or typical long-bone abnormalities such as arthrosis.
• Having a first-degree relative with NF1.

Diagnostic criteria for type 2 neurofibromatosis (NF2)

At least one of the following three is required for diagnosis of NF2:

• Bilateral 8th nerve masses on MRI scan.
• A first-degree relative with NF2 for a unilateral 8th nerve mass.
• A first-degree relative with NF2 for an individual with at least two of the following:
  • Meningioma
  • Glioma
  • Schwannoma
  • Juvenile cataracts

  • Dermal features

    • Café au lait spots are often the first findings in NF1. They may be present at birth or may appear with time. They usually increase in size and number during childhood. 1-2 café au lait patches occur in 10% of the general population. Children with 3-5 café au lait patches, but no other signs of NF1, should be followed up, as they might have mosaic NF1 or NF2.
    • Axillary or inguinal freckles are rare at birth but appear throughout childhood and adolescence.
    • Café au lait patches and skin-fold freckling do not usually cause complications; however, some patients are distressed by the appearance of this pigmentation and may be helped by skin camouflage advice. There is no evidence to support the routine use of laser treatment for café au lait patches.
    • Hypopigmented macules may co-exist with café au lait spots in NF1 and are found in a similar distribution.
    • Urticaria pigmentosa may be seen in a small subset of infants. It is a collection of mast cells within the dermis.
    • Naevus anaemicus and benign cherry angiomas (Campbell de Morgan spots) are observed more frequently in NF1 than in the general population.
    • Juvenile xanthogranulomas are benign orange papules that appear transiently on the head and trunk in 1% of young children. The suggestion of an increased risk of chronic myeloid leukaemia in children with NF1 and xanthogranulomas has not been borne out and routine haematological testing is not recommended in this group.

    Neurofibromas

    • They may be in the skin or subcutaneous tissues. Deep lesions may require palpation for detection but cutaneous lesions may appear initially as small papules on the trunk, extremities, scalp, or face.
    • Cutaneous neurofibromas are found in the majority of NF1 individuals, are rare in early childhood but tend to develop in the late teens or early twenties. There may be an increase in numbers and a growth of existing lesions at puberty or in pregnancy.
    • Cutaneous neurofibromas rarely appear to undergo malignant transformation. However, they may catch on clothing and/or cause cosmetic embarrassment, stinging or itching.
    • Subcutaneous neurofibromas may be tender to touch and cause tingling in the distribution of the affected nerve. Malignant change occasionally occurs: if rapid growth occurs, refer to a specialist, as removal may result in nerve damage.
    • Plexiform neurofibromas are more diffuse growths that can be locally invasive and quite deep. There may be bony erosion and pain. They may also be accompanied by hyperpigmentation or hypertrichosis over the lesions. Risk of disfigurement from facial plexiform neurofibromas appears to be greatest during the first three years of life.
    • In NF2, sensorimotor polyneuropathy may be seen and there may be identifiable tumours along the relevant peripheral nerves.

    Ocular problems

    • Tumours of the optic nerve (gliomas) occur in about 15% of children with NF1.
    • They are often asymptomatic but, over time, tumours may cause visual acuity loss, abnormal colour vision, visual field loss, squint, pupillary abnormalities, pale optic disc, proptosis and hypothalamic dysfunction. Risk is highest in those aged under 7 years. Young children rarely complain of early visual impairment and sometimes it is not picked up until it is advanced, with bilateral visual loss. Parents should be aware to look out for potential indicators of problems - failure to pick up small toys or bumping into things.
    • The most common presentation is asymmetrical visual field defects. Optic nerve gliomas occasionally start to cause symptoms in older children or even adults. They can also undergo spontaneous regression.
    • Lisch nodules are usually only seen by slit lamp. Occasionally, they can be visible via the ophthalmoscope.
    • Patchy choroidal abnormalities and corkscrew retinal vessels are sometimes seen in patients with NF1.
    • In NF2, posterior subcapsular or juvenile cataracts can precede CNS symptoms. These cataracts may progress over time, impairing visual acuity. Some have retinal hamartomas or epiretinal membranes that are not always significant to vision.

    Skeletal problems

    • Sphenoid dysplasia usually causes no problem but can cause herniation through the bony defect. Patients with plexiform neurofibroma of the eyelid or temporal region often have ipsilateral sphenoid dysplasia.
    • Congenital pseudoarthrosis may be apparent at birth. Bowing of the tibia is the most common presentation and occurs in about 2% of those with NF1. Thinning and angulation of long bones with prominence of the anterior tibia and progressive deformity can occur throughout early childhood. Bowing of the forearm is less common. Fracture can occur spontaneously or after trivial injury, and NF should be considered as a differential for non-accidental injury.
    • The thoracic cage may be asymmetrical with flaring or prominence of the inferior ribs. It affects some children with NF1 but rarely requires surgical correction.
    • Scoliosis may occur with or without kyphosis. This may become evident in childhood or adolescence and adolescent girls are affected rather more often than boys. If it starts before the age of 10 years, scoliosis has a poor prognosis and is likely to be rapidly progressive. Scoliosis detected in adolescence should be followed, but is less likely to require orthopaedic intervention.
    • NF1 causes disruption of bone maintenance and reduced bone mineral density. Be vigilant about the possibility of osteoporosis.

    Neurological problems

    

    • Neurological complications develop from tumours and malformations, including aqueduct stenosis. Skull deformity due to sphenoid wing dysplasia can lead to pulsating exophthalmos.
    • Severe scoliosis can deform the spine, causing cord compression and respiratory compromise.
    • Pressure on peripheral and spinal nerves and the spinal cord will also have neurological sequelae.
    • Epilepsy is usually mild and only occurs in 6-7% of NF1 individuals.
    • Carotid artery stenosis/occlusion and cerebral aneurysm may occur with NF1.
    • Patients should be advised to seek urgent help where they experience acute or progressive sensory disturbance, motor deficit and inco-ordination or sphincter disturbance, which may indicate an intracranial lesion or spinal cord compression.
    • Cognitive problems are the most common neurological complication and usually present as an IQ in the low average range. Specific learning problems occur in one- to two-thirds of children with NF1. The cause of cognitive problems in NF is not known. Children and adolescents with NF are more likely to suffer attention deficit hyperactivity disorder (ADHD); incidence is high, at around 40%.

    • Cardiovascular problems

      • Congenital heart disease (pulmonary stenosis and hypertension) are associated with NF.
      • Renal artery stenosis occurs in approximately 2% of those with NF1, so NF should be a diagnosis considered in hypertensive children, young adults and pregnant women, and refractory hypertension in older individuals and those with an abdominal bruit.
      • Phaeochromocytoma similarly occurs in approximately 2% of those with NF1. About 12% of these tumours are malignant.

      Other clinical problems/complications may include:
      

      • Gastrointestinal (GI) - abdominal bloating, pain, dyspepsia, haemorrhage and constipation may suggest a GI neurofibroma. Carcinoid tumours may give rise to facial flushing, diarrhoea, right-sided cardiac lesions, facial telangiectasiae and bronchoconstriction. GI stromal tumours are also associated with NF1 and may present with anaemia and GI bleeding.
      • Psychological - disfigurement and the unpredictable course of NF may cause anxiety and depression. Parents of children with NF1 report a profound impact of NF on physical, social, behavioural and emotional aspects of their quality of life.Children with NF1 can have difficulties forming friendships and developing social skills.
      • Endocrine - precocious puberty occurs in about 3% and is associated with tumours of the optic chiasma.
      • Obstetric - there appears to be an increased risk of perinatal complications in NF1, with a higher stillbirth rate, intrauterine growth restriction and Caesarean section rate. During pregnancy, neurofibromas may grow in size and number and there is the risk of cord compression if spinal plexiform neurofibromas expand. Obstetricians should also ensure pelvic neurofibromas do not impede delivery of the baby.

      Investigations

      Baseline brain and spinal MRI scanning and routine imaging of the chest and abdomen to identify asymptomatic tumours do not influence management and are not advised.

      Plain X-ray

      • Dural ectasia is often seen on X-rays of the vertebral column. It may suggest future progressive scoliosis.
      • X-rays are required if:
        • There are possible modelling defects of the long bones or ribs.
        • There is concern that a bony lesion may be adjacent to a plexiform neurofibroma.
        • Scoliosis is seen on clinical examination.
        • Bone pain exists.

      Scans

      CT or MRI scanning may be required:
      

      • MRI is preferred for diagnostic head imaging. Hyper-intense lesions on T2-weighted brain MRI are probably caused by aberrant myelination or gliosis and are pathognomonic of NF1. They occur most commonly in children aged 8-16 years but tend to have disappeared by adulthood. They are associated with cognitive impairment. The presence of these lesions can assist in diagnosing NF1 but MRI under anaesthetic is not warranted for this purpose in young children.¹
      • Consider CT or MRI scans to check ventricular size if head circumference in an infant is increasing rapidly. Hydrocephalus is rare in NF1.
      • MRI can evaluate the optic nerves or optic chiasma. It is indicated for optic nerve pallor, visual changes, proptosis, or precocious puberty.
      • Consider MRI scans of the head if headaches increase in frequency or intensity over time. Brain tumours are more common in NF2 than NF1.
      • MRI can also be useful to evaluate mediastinal masses, spinal cord tumours, deep plexiform neurofibromas, abdominal and pelvic lesions and neurofibromas of the brachial or sacral plexus.

      Electrophysiology

      • If seizures occur, EEG is required in assessment.
      • Myelography is occasionally helpful to clarify the extent of a spinal cord tumour but, generally, MRI alone is enough.
      • Visual evoked potentials (VEPs) may be helpful in detecting optic nerve gliomas or assessing tumour progression with optic pathway tumours.

      Slit-lamp examination

      This usually requires the expertise of an ophthalmologist.
      

      • Slit-lamp examination may provide essential diagnostic information in older children and adults who present with only one clinical criterion such as multiple café au lait spots.
      • The frequency of Lisch nodules increases with age. They are seen in more than 95% of those with NF1 who are older than 10 years.
      • Slit-lamp examination is valuable to decide if the parents of an affected child carry the NF1 mutation, even in the absence of any other features of the disease.

      Genetic testing

      NF1 mutational analysis may clarify the diagnosis in some ambiguous cases but is not advocated routinely.

      Histology

      Biopsy of asymptomatic cutaneous neurofibromas should not be undertaken for diagnostic purposes in individuals with clear-cut NF1.
      
      Tests for hearing and vestibular function are important in NF2.

      Differential diagnosis

      Type 1 or type 2 neurofibromatosis (NF)?
      

      • Type 1 tends to present in childhood or adolescence, whilst type 2 usually presents in adults aged under 40 years, and mostly in the 20s.
      • Around 45% of type 2 present with hearing problems such as deafness and tinnitus, with or without loss of balance or facial weakness due to vestibular schwannomas.
      • Café au lait spots are the usual, early feature of NF1 but there are rarely more than six spots in NF2. It rarely shows axillary or inguinal freckles.
      • Multiple subcutaneous lesions can be indistinguishable between the two.
      • Posterior subcapsular lenticular opacities, even in childhood, would be suggestive of NF2, whereas Lisch nodules would be diagnostic of NF1.

      Other conditions with café au lait patches include:
      

      • McCune-Albright syndrome.
      • DNA repair syndromes.
      • Hereditary non-polyposis cancer of the colon.

      Other conditions with pigmented macules include:
      

      • Neurocutaneous melanosis.
      • Peutz-Jeghers syndrome.

      Other localised overgrowth syndromes include:
      

      

      • Klippel-Trénaunay syndrome.
      • Proteus' syndrome
      • .

        Management

        Care is largely a matter of monitoring progress and intervening appropriately where tumours produce pressure symptoms or behave in a manner suggestive of malignant change.
        
        All children with uncomplicated disease should be assessed annually, ideally by one paediatrician in each area to facilitate co-ordinated care. Young adults (16-25 years) will need education about NF and its possible complications, including reproductive counselling.
        

        • Height and weight should be charted and abnormal pubertal development assessed.
        • Review visual symptoms. Those aged under 7 years should have annual visual acuity and fundoscopy testing. Baseline assessment of colour vision and visual fields should be undertaken once the child is able to cope with the test.
        • Check the skin for new neurofibromas and progression of existing ones. Irritation does not usually respond to antihistamines and the benefit of mast cell stabilisers is uncertain; advise avoiding excessive heat. Emollients may be helpful. Cutaneous neurofibromas can be removed if they catch in clothing or cause other problems.
        • Plexiform neurofibromas may be locally invasive. Determine the extent of involvement and any evidence of bony erosion or nerve entrapment.
        • Check for skeletal involvement, including scoliosis, hemihypertrophy, and long-bone modelling defects. Check head circumference in the first three years, as rapid increase may indicate tumour or hydrocephalus.
        • Examine the heart, looking for murmurs. Check blood pressure at every visit and take prompt action if there is hypertension. Any unexplained murmur should be referred for a cardiology opinion and echocardiography.
        • Ask about the child's neurodevelopment, to note any learning disabilities and take early action.

        Older adults should be offered the opportunity of attending clinic on an annual basis: adults with severe disease will usually already have been identified by this stage and need lifelong monitoring in a dedicated specialist clinic; those with mild disease have a much lower risk of complications, but should have a minimum of annual blood pressure checks and be aware to consult their GP if they encounter unusual symptoms (who can then refer them on if necessary).

        Drugs

        There are no specific drugs for the disorder, although they may be needed for secondary problems such as hypertension, epilepsy or ADHD.

        Surgery

        Neurofibromas

        • Neurofibromas that press on vital structures, obstruct vision, or grow rapidly need urgent attention.
        • Plexiform neurofibromas can be difficult. They often recur after resection because there are residual cell rests deep in soft tissues.
        • Neurofibromas on the scalp, along the hairline, or around the waist where clothes rub can cause irritation and discomfort and are worthy of removal.
        • In NF2, there has been some success with cochlear implants for bilateral acoustic neuroma.

        Spinal cord tumours

        • Prompt attention is required if neurological symptoms appear. Resection of spinal cord tumours is quite difficult but may be necessary to prevent progressive paraplegia or quadriplegia.
        • For some patients, surgical intervention may not cure but it provides valuable palliation.

        Orthopaedic surgery

        • Rapidly progressive scoliosis or severe bony defects need urgent attention.
        • Early referral for scoliosis gives the best results.
        • Long-bone defects can require amputation but mode bracing and casting techniques have reduced the need.

        Vascular surgery

        • Percutaneous transluminal renal artery angioplasty (PTRAA) may be effective in treating some renal artery stenosis due to fibromuscular dysplasia.
        • Others may require surgical repair and anastomosis of the renal artery.

        Complications

        Many complications have already been mentioned.
        Individuals with NF are at an increased risk of brain tumours, leukaemia, and other malignancies of neural crest origin, including neurofibrosarcomas. Brain tumours are rather more common in NF2. Occasionally, peripheral nerve sheath tumours undergo malignant change in NF1 but not NF2. The risk of malignant change is usually rated as quite low but a study from Manchester suggested that the lifetime risk for an individual with NF1 is 8 to 13% with a mean age of diagnosis of 26 and a 5-year survival rate of 21%,giving cause for concern.
        

        
       
     

    Prognosis

    • Type 1, in particular, is so varied in its manifestation, that it is difficult to predict outcome, as phenotype is so variable even within affected families.
    • Most people with NF1 lead relatively long and healthy lives, but it does reduce life expectancy by around 15 years. The major complications are hypertension and malignancy.
    • NF2 generally has a worse prognosis. Much of the morbidity from these tumours results from their treatment. Early detection and prompt attention to complications may reduce overall morbidity and mortality.

    Prevention

    The risk of an affected individual with type 1 neurofibromatosis (NF1) or type 2 neurofibromatosis (NF2) transmitting the disease to their child is 50% but this cannot predict the severity of any inherited disease. When the complications that cause lifelong morbidity or early mortality in NF1 are considered, the risk of having a severely affected child is about 1 in 12.
    
    Where parents have had the first affected child known in a family, they should be examined for cutaneous stigmata or Lisch nodules. They may be found to have a segmental or mosaic form of NF and thus be at risk of having another affected child. Where there are no clinical signs, their affected child's condition will have arisen due to a de novo mutation, and the risk to the parent of having another child with NF1 is extremely small (less than 1%).
    
    The NF1 gene mutation can now be found in 85-95% of cases. Prenatal testing is possible using fetal DNA extracted from chorionic villous sampling or from amniocentesis. Many do not want prenatal assessment because it cannot determine disease severity. Pre-implantation genetic diagnosis is also available. Genetic counselling prior to conception should be advised in all individuals with NF.

Neurosurgery for Hydrocephalus

 History of the Procedure

Hydrocephalus was first described by Hippocrates. Hydrocephalus was not treated effectively until the mid 20th century, when the development of appropriate shunting materials and techniques occurred. Interestingly, at the beginning of the 20th century, doctors (including urologists) attempted to introduce scopes into the ventricular system. Attempts were also made to remove the choroid plexus, which generates much of the cerebrospinal fluid (CSF), in an attempt to treat hydrocephalus. Today, the focus of hydrocephalus research is on pathophysiology, valve design in shunting, and minimally invasive techniques of treatment.

An image depicting hydrocephalus can be seen below.

 Noncommunicating obstructive hydrocephalus caused by obstruction of the foramina of Luschka and Magendie. This MRI sagittal image demonstrates dilatation of lateral ventricles with stretching of corpus callosum and dilatation of the fourth ventricle. 

Problem

Hydrocephalus is the abnormal rise in CSF volume and, usually, pressure, that results from an imbalance of CSF production and absorption.

Epidemiology

Frequency

The overall incidence of hydrocephalus is unknown. When cases of spina bifida are included, congenital hydrocephalus occurs in 2-5 births per 1000 births. Incidence of acquired types of hydrocephalus is unknown.
Tanaka et al concluded that the incidence of idiopathic normal pressure hydrocephalus was 1.4% in their study of an elderly Japanese population.

Etiology

The etiology of hydrocephalus in congenital cases is unknown. Very few cases (< 2%) are inherited (X-linked hydrocephalus). The most common causes of hydrocephalus in acquired cases are tumor obstruction, trauma, intracranial hemorrhage, and infection.

Pathophysiology

Hydrocephalus can be subdivided into the following 3 forms:

• Disorders of CSF production: This is the rarest form of hydrocephalus. Choroid plexus papillomas and choroid plexus carcinomas can secrete CSF in excess of its absorption.
• Disorders of CSF circulation: This form of hydrocephalus results from obstruction of the pathways of CSF circulation. This can occur at the ventricles or arachnoid villi. Tumors, hemorrhages, congenital malformations (such as aqueductal stenosis), and infections can cause obstruction at either point in the pathways.
• Disorders of CSF absorption: Conditions, such as the superior vena cava syndrome and sinus thrombosis, can interfere with CSF absorption. Some forms of hydrocephalus cannot be classified clearly. This group includes normal pressure hydrocephalus and pseudotumor cerebri. 
   

  Presentation

  The various types of hydrocephalus can present differently in different age groups.
  Acute hydrocephalus typically presents with headache, gait disturbance, vomiting, and visual changes. In infants, irritability or poor head control can be early signs of hydrocephalus. When the third ventricle dilates, the patient can present with Parinaud syndrome (upgaze palsy with a normal vertical Doll response) or the setting sun sign (Parinaud syndrome with lid retraction and increased tonic downgaze). Occasionally, a focal deficit, such as sixth nerve palsy, can be the presenting sign. Papilledema is often present, although it may lag behind symptomatology. Infants present with bulging fontanelles, dilated scalp veins, and an increasing head circumference. When advanced, hydrocephalus presents with brainstem signs, coma, and hemodynamic instability.
  Normal pressure hydrocephalus has a very distinct symptomatology. The patient is older and presents with progressive gait apraxia, incontinence, and dementia. This triad of symptoms defines normal pressure hydrocephalus.
  
  

  Indications

  Most cases of symptomatic hydrocephalus need to be treated before permanent neurologic deficits result or neurologic deficits progress.
  When an etiologic factor is known, hydrocephalus can be treated with temporary measures while the underlying condition is treated. Examples of temporary treatment measures are ventriculostomy until a posterior fossa tumor is resected or lumbar punctures in a neonate with intraventricular hemorrhage until the blood is absorbed and normal cerebrospinal fluid (CSF) absorption resumes.

  Relevant Anatomy

  See Intraoperative details for a discussion of relevant anatomy.

  Contraindications

  Few cases of hydrocephalus should not be treated. Cases in which treatment should not be implemented include the following:
  

  • The patient in whom a successful surgery would not affect the outcome (eg, a child with hydranencephaly)
  • In ventriculomegaly of senescence, the patient who does not have the symptom triad
  • Ex vacuo hydrocephalus is merely the replacement of lost cerebral tissue with cerebrospinal fluid. Because no imbalance in fluid production and absorption exists, this technically is not hydrocephalus.
  • Arrested hydrocephalus is defined as a rare condition in which the neurologic status of the patient is stable in the presence of stable ventriculomegaly. The diagnosis must be made extremely carefully because children can present with very subtle neurological deterioration (eg, slipping school performance) that is difficult to document.
  • Benign hydrocephalus of infancy is found in neonates and young infants. The children are asymptomatic, and head growth is normal. CT scan shows mildly enlarged ventricles and subarachnoid spaces.

   

Spinal Cord Abscess

Background

Intramedullary spinal cord abscesses are infrequently encountered in everyday neurosurgical practice. Hart reported the earliest documented spinal cord abscess in 1830. Since then, fewer than 100 cases have been reported in the medical literature. With modern antibiotics and neurosurgical techniques, even fewer of these infections are expected to be encountered in the future.
Since the original publication of this article, several other case reports have been published that discuss intramedullary spinal cord abscesses.These case reports, while detailing several unusual presentations of patients with intramedullary spinal cord abscesses, add little to the core concepts promulgated in the original article. Patients with intramedullary spinal cord abscesses present with neurological findings related to the level of spinal cord involvement; MRI with gadolinium is still the procedure of choice for early diagnosis; and successful outcomes depend upon early diagnosis, aggressive surgical treatment, and appropriate antibiotic treatment following surgery. Even when these guidelines are followed, 70% of patients are left with neurological sequelae.
see the image below:-

 Abscess that compresses the spinal cord and its vasculature.

Problem

Spinal cord abscesses arise in spinal cord parenchyma and can be solitary or multiple, contiguous or isolated, and chronic or acute, depending upon the organism and individual patient. As may be expected, solitary lesions are more common and most likely appear in the thoracic cord. Holocord abscesses have been reported in approximately 5 patients. Some authors divide these abscesses into primary and secondary, depending on the source of infection. Abscesses are considered primary when no other infection source can be found. Secondary abscesses arise from another infection site, either distant from or contiguous to the spinal cord, most commonly from the lung, spine, heart valves, and genitourinary system. Intramedullary spinal cord abscesses most commonly arise from a secondary source such as the cardiopulmonary system or from a contiguous source such as the mediastinum. These classifications rarely affect treatment or patient outcome.

Epidemiology

Frequency

Fewer than 100 cases have been reported. Spinal cord abscesses occur more frequently in males than females with a peak incidence in the first and third decades of life. Too few cases have been reported to define any racial predilection. Patients with a history of intravenous drug abuse are at particularly high risk, as are other immunocompromised patients such as those with HIV, diabetes, or multiple organ failure.

Etiology

The most common organisms cultured from spinal cord abscesses include Staphylococcus and Streptococcus species, followed by gram-negative organisms. Mixed flora abscesses are also encountered. Other unusual organisms have been reported, including Actinomyces, Listeria, Proteus, Pseudomonas, Histoplasma capsulatum, and the tapeworm Sparganum. In 1899, Hoche demonstrated that abscesses may occur in areas of infarction, thus explaining the common incidence of septic spread to the lower half of the thoracic cord. The Batson plexus (the confluence of epidural veins in the spinal canal) may contribute to the origin of an abscess by allowing organisms to lodge and thus develop in the spinal cord and its surrounding parenchyma.

Pathophysiology

Spinal cord abscesses have many of the same characteristics of abscesses in other locations. Blood vessel involvement surrounded by an area of infection characterizes hematogenous spread. Areas of softening and early abscess formation characterize subacute infections (1-2 wk duration), whereas a classic abscess wall of fibrotic gliosis surrounding necrotic purulent material characterizes chronic infections. However, spinal cord abscesses do not destroy fiber tracts. Instead, the abscess displaces fiber tracts and spreads along axonal pathways.

Presentation

As with most neurological diseases, signs and symptoms depend upon the abscess location and duration. In an acute presentation, symptoms of infection (eg, fever, chills, back pain, malaise) are common. Neurological symptoms and signs include weakness, paresthesia, dysesthesia, bladder and bowel incontinence, and acute paraplegia. The neurological signs and symptoms are dependent upon the location in the spinal cord of the abscess; the most common location for an intramedullary abscess is the thoracic spinal cord. Clinical symptoms are similar to those of patients with epidural abscesses, but percussion tenderness is not noted.
In more chronic cases, signs and symptoms mimic those of an intramedullary tumor, and neurological symptoms predominate over those of a systemic infection. The neurological progression is gradual. A high degree of awareness is necessary to diagnose chronic spinal cord abscess; in contrast, acute abscesses are generally encountered in extremely ill patients presenting with acute onset of back pain.

Indications

The presumptive diagnosis of intramedullary abscess requires prompt definitive diagnosis. This of course necessitates demonstration of an infection with subsequent identification of that organism; therefore, laminectomy to diagnose and culture the organism is usually required.

Relevant Anatomy

Since abscesses may occur anywhere along the spinal axis, anatomy varies with location involved. As noted above, the most common location for an intramedullary abscess is the posterior thoracic spinal cord.

Contraindications

No well-defined contraindications exist to treating spinal cord abscesses.

Closed Head Trauma

 Background

In the United States, the incidence of closed head injury is estimated to be approximately 200 cases per 100,000 persons per year.In a population of 291.6 million people, this rate equates to more than 570,000 patients annually.Approximately 15% of these patients succumb to the injury upon arrival to the emergency department.
Traumatic injuries remain the leading cause of death in children and in adults aged 45 years or younger. Head injuries cause immediate death in 25% of acute traumatic injuries.Traumatic brain injury (TBI) results in more deaths than does trauma to other specific body regions.Penetrating intracranial injuries have worse outcomes than closed head injuries.Motor vehicle collisions (MVCs) are the most common cause of closed head injuries for teenagers and young adults.Alcohol or drug use contributes to as many of 38% of cases of severe head trauma in younger patients.A recent development has been the apparent increase in brain injuries among the elderly; this increase is thought to be related to the use of anticoagulant and antiplatelet drugs.
A CT scan of left frontal acute epidural hematomais shown below.

CT scan of left frontal acute epidural hematoma (black arrow) with midline shift (white arrow). Note the left posterior falx subdural hematoma and left frontoparietal cortical contusion.
Head injury significantly contributes to deaths from trauma.Annual mortality from closed head injuries is approximately 100,000 patients or 0%, 7%, and 36% of mild, moderate, and severe head injuries, respectively. Patients with severe head injury have a 30-50% mortality rate, and those who survive are often left with severe neurological deficits that may include a persistent vegetative state.Permanent disability in survivors ranges from 10-100%, depending on the severity of the injuries. This produces more than 90,000 newly disabled patients annually, including 2500 who are in a persistent vegetative state.
The financial burden of head injuries in the United States is estimated to be $75-100 billion annually.Injuries to the central nervous system tend to be the most costly on a per-patient basis because they often result in debilitating physical, psychological, and psychosocial deficits that, in turn, require extensive long-term rehabilitation and care.
The last 3 decades have been alternately exhilarating and frustrating for clinicians and researchers interested in TBI. Laboratory and bedside research has greatly improved our understanding of posttraumatic cerebral pathophysiology. These new insights have failed to make the transition to clinically used therapies. Many of the major clinical trials of the last decades have been negative studies that have shown us what does not work. Demonstrating the efficacy of new treatments has been extraordinarily difficult.
 Pathophysiology
 Closed head injuries are classified as either primary or secondary. A primary injury results from the initial anatomical and physiological insult, which is usually direct trauma to the head, regardless of cause. A secondary injury results from hypotension, hypoxia, acidosis, edema, or other subsequent factors that can secondarily damage brain tissue (see Secondary injuries). Free radicals are thought to contribute to these secondary insults, especially during ischemia.
Primary injury
The primary injury usually causes structural changes, such as epidural hematoma, subdural hematoma, subarachnoid hemorrhage, intraventricular hemorrhage, or cerebral contusion.
Concussions
Cerebral concussion is defined as an altered mental state that may or may not include loss of consciousness that occurs as a result of head trauma. Concussion is also known as mild traumatic brain injury (MTBI). The American Academy of Neurology grading scale is widely used to categorize the degree of concussions.

Sport-related concussions are frequent, with 300,000 cases reported each year. Football players and boxers are particularly exposed to repetitive concussions, leading to the condition now known as chronic traumatic encephalopathy syndrome. Repetitive concussions may result in chronic subclinical motor dysfunctions linked to intracortical inhibitory system abnormalities.Parkinsonian cognitive decline due to strionigral degeneration is now a well-known consequence of repetitive concussions; cumulative diffuse axonal injury effects in the midbrain are due to increased vulnerability to shear forces in that region. Increasing a player’s neck strength may be an effective way to minimize the risk of future concussions, as studies with Hybrid III dummies seem to indicate.
Cerebral contusion
Cerebral contusions are commonly seen in the frontal and temporal lobes. They may accompany skull fracture, the so-called fracture contusion. The most worrisome trait of these contusions is their tendency to expand. This usually occurs from 24 hours to as long as 7-10 days after the initial injury. For this reason, cerebral contusions are often followed with a repeat head CT scan within 24 hours after injury.
Coup injuries (contusions) are caused by direct transmission of impact energy through the skull into the underlying brain and occur directly below the site of injury. Contrecoup injuries are caused by rotational shear and other indirect forces that occur contralateral to the primary injury. Rotational force causes the basal frontal and temporal cortices to impact or sweep across rigid aspects of the skull, the sphenoid wing, and petrous ridges. Delayed enlargement of traumatic intraparenchymal contusions and hematomas is the most common cause of clinical deterioration and death. However, progression of contusion is highly variable, and although most remain unchanged for days, a few enlarge, some quite rapidly.
In a retrospective study, well-known prognostic factors were found to predict contusion enlargement. The strongest prognostic factor is the presence of traumatic subarachnoid hemorrhage. The size of the intraparenchymal hemorrhage means that large lesions are probably in an active phase of progression at the time of the initial CT scan. The concurrent presence of a subdural hematoma was also predictive. Clinical features, such as the initial Glasgow Coma Score (GCS) and intracranial pressure (ICP), were not predictive of progression. The ideal time for a rescan is unclear, although most of the growth seems to occur within the first 24 hours of injury.
Epidural hematoma
The incidence of epidural hematomas is 1% of all head trauma admissions, as depicted in the image below. Epidural hematomas most commonly (85%) result from bleeding in the middle meningeal artery. Epidural hematomas, however, may occur in locations other than in the distribution of the middle meningeal artery. Such hematomas may develop from bleeding from diploic vessels injured by overlying skull fractures.Epidural hematomas are often associated with a "lucid interval," a period of consciousness between states of unconsciousness. The lucent period is presumed to end when the hematoma expands to the point that the brainstem is compromised.

Subdural hematoma
The most common surgical intracranial lesion is a subdural hematoma. These occur in approximately 20-40% of patients with severe injuries, as depicted in the image below. A surface or bridging vessel (venous) can be torn because the brain parenchyma moves during violent head motion. The resulting bleeding causes a hematoma to form in the potential space between the dural and arachnoid. A lucid interval is less likely to develop in this type of injury than in epidural hematomas. Subdural hematomas can be the result of an arterial rupture as well; these hematomas have the peculiar location in the temporoparietal region and differ in form from those caused by the bridging vein rupture, which typically rupture in the frontoparietal parasagittal region. Hematoma thickness and the midline shift of the brain are often analyzed; when the midline shift exceeds the hematoma thickness (positive displacement factor), a poorer prognosis has been found.

Intraventricular hemorrhage
An intraventricular hemorrhage is another intracerebral lesion that often accompanies other intracranial hemorrhages, as depicted in the image below. Intraventricular blood is an indicator of more severe head trauma. Intraventricular blood also predisposes the patient to posttraumatic hydrocephalus and intracranial hypertension, which may warrant placement of an intraventricular catheter (if emergent drainage needed) or ventriculoperitoneal shunt for chronic hydrocephalus.

CT scan of bilateral acute intraventricular hemorrhages (black arrow). Note the comminuted skull fractures that involve bilateral frontal, temporal, and parietal bones (white arrow). Note the ischemic changes in both frontal lobes, subarachnoid hemorrhages in the intrahemispheric fissure and left frontal lobe, and multiple intraparenchymal hemorrhages in both frontal poles. 


Diffuse axonal injury
Despite the absence of any intracranial mass lesion or history of hypoxia, some patients remain unconscious after a TBI. Brain MRI studies have demonstrated a clear correlation between white matter lesions and impairment of consciousness after injury. The deeper the white matter lesion, the more profound and persistent the impairment of consciousness.
The usual cause for persistent impairment of consciousness is the condition referred to as diffuse axonal injury, as depicted in the image below. Approximately 30-40% of individuals who die from TBI reveal postmortem evidence of DAI and ischemia.This type of injury commonly results from traumatic rotation of the head, with mechanical forces that act on the long axons, leading to axonal structural failure. DAI is caused by an acceleration injury and not by contact injury alone. The brain is relatively incompressible and does not tolerate tensile or shear strains well. Slow application of strain is better tolerated than rapid strain. The brain is most susceptible to lateral rotation and tolerates sagittal movements best.

MRI of the brain that shows diffuse axonal injury (DAI) and hyperintense signal in the corpus callosum (splenium), septum pellucidum, and right external capsule. 


Recent studies suggest that the magnitude of rotational acceleration needed to produce DAI requires the head to strike an object or surface. These factors also increase the likelihood that DAI will be accompanied by other intracranial lesions.These mechanical forces physically dissect these axons into proximal and distal segments. If a sufficient number of axons are involved, profound neurologic deficits and unconsciousness may ensue.
These same forces may act on the cerebral circulation, causing disruption of vessels and various forms of micro–intracerebral hemorrhages and macro–intracerebral hemorrhages, including Duret hemorrhages, which are commonly lethal when they occur in the brainstem. Duret hemorrhages of the midbrain and pons are small punctate hemorrhages that are often caused by arteriole stretching during the primary injury, as depicted in the image below. They may also result during transtentorial herniation as a secondary injury when arterial perforators are compressed or stretched.

MRI of the brain (sagittal view) that shows a Duret hemorrhage in the splenium of the corpus callosum. 

A recent study indicates that DAI and younger age may contribute to an increased risk of developing dysautonomia.

Secondary injuries

Secondary insults can take many forms and can be summarized as follows:

• Secondary intracranial insults to the brain
  

  • Hemorrhage
  • Ischemia
  • Edema
  • Raised intracranial pressure (ICP)
  • Vasospasm
  • Infection
  • Epilepsy
  • Hydrocephalus
• Secondary systemic insults to the brain
  

  • Hypoxia
  • Hypercapnia
  • Hyperglycemia
  • Hypotension
  • Severe hypocapnia
  • Fever
  • Anemia
  • Hyponatremia

The major focus in the management of acute closed head injury is the prevention of secondary injuries and the preservation of neurological functions that are not damaged by the primary injury.
Posttraumatic vasospasm can be a cause of ischemic damage after severe traumatic brain injury, with parenchymal contusions and fever being risk factors. Diffuse mechanical injury and activation of inflammatory pathways may be secondary mechanisms for this vasospasm. Patients with parenchymal contusions and fever may benefit from additional screening.
Cerebral ischemia
Cerebral ischemia is inadequate oxygen perfusion to the brain as a result of hypoxia or hypoperfusion. The undamaged brain tolerates low PaO₂ levels better than the severely injured brain. Traumatized brain tissues are very sensitive to even moderate hypoxia (90 mm Hg). Gordon and Ponten proposed 2 explanations for this phenomenon: Respiratory alkalosis may shift the oxygen-hemoglobin curve to the left, thereby increasing the affinity of the hemoglobin to the oxygen and decreasing the ease of oxygen release, and  uneven cerebral blood flow (CBF) may result from focal vasospasm with loss of focal autoregulation in the area of injured brain tissue.Approximately one third of patients with severe head injuries have been demonstrated to experience ischemic levels of CBF
CBF is normally kept constant over a range (about 50-150 mm Hg) of cerebral perfusion pressure, as depicted in the image below. This is made possible by adjustments in vascular tone known as autoregulation (solid line). In patients with brain trauma, this autoregulation may malfunction, and CBF may become dependent on the CPP (dashed lines). Autoregulation is absent, diminished, or delayed in 50% of patients with severe head injuries.The lowest CBF values occur within the first 6-12 hours after injury.The overall outcome of patients who experience ischemia is much worse than that of initially nonischemic patients.The initial ischemia is thought to cause permanent irreversible damage even if CBF is eventually optimized. The use of Xenon CT scan to measure CBF is now part of the armamentarium to diagnose and treat abnormalities in the CBF.

 Cerebral blood flow/cerebral perfusion pressure chart. 
Brain edema
Brain edema is another form of secondary injury that may lead to elevated ICP and frequently results in increased mortality. Brain edema is categorized into 2 major types: vasogenic and cellular (or cytotoxic) edema.
Vasogenic edema occurs when a breach in the blood-brain barrier allows water and solutes to diffuse into the brain. Most of this fluid accumulates in the white matter and can be observed on head CT scans as hypodense white matter (on T1-weighted images) or as a bright signal area on the T2-weighted MRI. The mechanism of cellular (cytotoxic) edema is less clear. Theories include the increased uptake of extracellular potassium by the injured brain cells or the transport of HCO₃^- and H⁺ for Cl^- and Na⁺ by the injured brain tissue as the mechanism of insult.
In one study, diffusion-weighted MR imaging was used to evaluate the apparent diffusion coefficient (ADC) in 44 patients with TBI (GCS < 8) and in 8 healthy volunteers. Higher ADC values have been associated with vasogenic edema, and lower ADC values have been associated with a predominantly cellular form of edema. Regional measurements of ADC in patients with focal and diffuse injury were computed. The final conclusion was that the brain swelling observed in patients with TBI appears to be predominantly cellular, as signaled by low ADC values in brain tissue with high levels of water content.

Epidemiology

Frequency

United States

The incidence of closed head injury is estimated to be approximately 200 cases per 100,000 persons per year.

Mortality/Morbidity

Traumatic injuries remain the leading cause of death in children and in adults aged 45 years or younger (see Background).

Race

The incidence in specific ethnic groups varies.

Sex

The incidence varies in males and females.

Age

The incidence varies by age, but children and young people experience closed head trauma more often than older populations.