Head Trauma


17	Head Trauma

EPIDEMIOLOGY

Estimates of the annual number of head injuries in the United States range from 500,000 to 1.5 million, with the large majority being mild in severity. In young adults, motor vehicle accidents are the most common cause of head trauma, whereas in the elderly, falls are the most common. Men are more often the victims of head trauma than are women, by a ratio of at least 2:1.

TYPES OF HEAD TRAUMA

EPIDURAL HEMATOMA

An epidural hematoma is an accumulation of blood between the skull and dura mater. It is usually the result of a severe head injury with a temporal bone fracture and resulting laceration of the middle meningeal artery. Less frequently, laceration of the middle meningeal vein or a dural venous sinus may produce an epidural hematoma. The classic presentation of epidural hematoma is a “lucid interval” in which the patient has preserved consciousness immediately after the precipitating event, followed by a decline in the level of consciousness, often with rapid progression to coma as the hematoma enlarges. Brain herniation, especially uncal herniation (see later discussion), may develop as a result of the hematoma expansion. The characteristic computed tomography (CT) scan appearance of an epidural hematoma is a lens-shaped hyperdense lesion between the skull and dura (Fig. 17-1). Surgical evacuation is required and, if performed in a timely fashion, can be life-saving.

FIGURE 17-1. Computed tomographic scan of the head demonstrating the typical hyperdense lens-shaped appearance of an epidural hematoma (arrows). Note the compression of the ipsilateral ventricles and modest midline shift. (Reproduced with permission from Daffner RH. Clinical Radiology: The Essentials. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.)

SUBDURAL HEMATOMA

A subdural hematoma is an accumulation of blood between the dura mater and the brain. It results from tearing of bridging veins that connect the surface of the brain and the dural sinuses. Subdural hematoma may have an acute or chronic presentation. Acute subdural hematoma develops shortly after head trauma and can be life-threatening. Headache is the most common symptom, but the hematoma may also lead to contralateral hemiparesis, seizures, and a wide variety of cortical dysfunction. If sufficiently large, a subdural hematoma can increase intracranial pressure (ICP), with a resulting diminution in the level of consciousness. The CT scan in Figure 17-2 shows a subdural hematoma as a crescent-shaped hyperdensity overlying the brain surface and underlying the skull. Subdural hematoma can be distinguished radiologically from an epidural hematoma by its ability to cross suture lines. Acute subdural hematoma may require treatment with surgical drainage depending on its size, severity, and clinical progression.

FIGURE 17-2. Computed tomographic scans of the head showing subdural hematomas overlying the right cerebral hemisphere: a smaller hematoma with classic crescent shape in A and major mass effect with compression of the right lateral ventricle and marked shift of the midline in B. (Modified with permission from Haines DE. Neuroanatomy in Clinical Context. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2014. Figure 4-5.)

Chronic subdural hematoma typically develops after mild head trauma and is more common in the elderly, particularly those who are anticoagulated. Like the acute variety, chronic subdural hematoma may produce one of several neurologic symptoms, including headache, hemiparesis, seizures, and behavioral changes. A chronic subdural hematoma may resolve on its own; indications for operation include rapidly expanding lesions and progressive clinical deficits. Anticoagulation should be discontinued to allow the best chance for recovery.

CONCUSSION

A concussion is an alteration of brain function produced by head trauma. The symptoms of a concussion are the result of a functional rather than structural change, and brain imaging studies are typically normal. Patients may have loss of consciousness (though this is not required for the diagnosis of concussion), short periods of amnesia for events that occurred before the injury (retrograde amnesia), and difficulty learning new material after the incident (anterograde amnesia). The severity of a concussion is correlated with the duration of loss of consciousness and consequent amnesia. Other consequences of concussion include headache, disorientation, dizziness and vertigo, nausea, and cortical blindness. Concussions are frequent in sporting events, particularly in children. Athletes who are suspected of having had a concussion should be removed from play. There is no clear consensus for when return to play should be allowed, but gradual reintroduction of activity is recommended until an athlete is asymptomatic, because a history of concussions increases the risk for future concussions.

POSTCONCUSSION SYNDROME

Postconcussion syndrome is usually the consequence of mild traumatic brain injury. The cause of the syndrome is unclear, but structural, biochemical, and psychological components have been implicated. Features of the syndrome include headache, dizziness, sleep disturbance, cognitive impairment, and behavioral abnormalities such as irritability. Neuroimaging studies are almost always normal. Pending litigation or workers’ compensation issues and depression are associated with prolonged postconcussion syndrome. Management should focus on the individual components of the syndrome, with treatment of headache, sleep disturbance, and psychological problems, including mood problems.

FIGURE 17-3. Diffuse axonal injury shown on magnetic resonance imaging with fluid-attenuated inversion recovery sequences.

DIFFUSE AXONAL INJURY

Diffuse axonal injury is associated with severe head trauma and may be seen on CT as multiple areas of punctate hemorrhage in the deep white matter and corpus callosum (Fig. 17-3). In many cases, though, it is not well visualized with standard neuroimaging studies. The presence of diffuse axonal injury is usually associated with poor prognosis.

KEY POINTS

●Epidural hematoma is usually caused by laceration of the middle meningeal artery; it is often clinically associated with a “lucid interval.”

●Subdural hematoma is usually caused by tearing of bridging veins and can produce a variety of neurologic deficits including headache, hemiparesis, and seizures.

●Concussion is a loss or alteration of consciousness produced by head injury and is usually accompanied by normal neuroimaging.

●Components of the postconcussion syndrome include headache, dizziness, cognitive impairment, sleep disturbance, and behavioral abnormalities.

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