Head injury refers to trauma to the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in the medical literature.
The incidence (number of new cases) of head injury is 300 per 100,000 per year (0.3% of the population), with a mortality of 25 per 100,000 in North America and 9 per 100,000 in Britain. Head trauma is a common cause of childhood hospitalization.
Common causes of head injury are traffic accidents, home and occupational accidents, falls, and assaults. Bicycle accidents are also a common cause of head injury-related death and disability, especially among children.
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull.
Head injuries may be closed or open. A closed (non-missile) head injury is one in which the skull is not broken. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area.
A head injury may cause a minor headache skull fracture, which may or may not be associated with injury to the brain. Some patients may have linear or depressed skull fractures.
If intracranial hemorrhage occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hemorrage include subdural, subarachnoid, extradural, and intraparenchymal hematoma. Craniotomy surgeries are used in these cases to lessen the pressure by draining off blood.
Brain injury can be at the site of impact, but can also be at the opposite side of the skull due to a contrecoup effect (the impact to the head can cause the brain to move within the skull, causing the brain to impact the interior of the skull opposite the head-impact).
If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull causing additional impacts, or the brain may stay relatively still (due to inertia) but be hit by the moving skull (both are contrecoup injuries).
Specific problems after head injury can include:
Mild concussions are associated with sequelae. However, a slightly greater injury is associated with both anterograde and retrograde amnesia (inability to remember events before or after the injury). The amount of time that the amnesia is present correlates with the severity of the injury. In all cases the patients develop postconcussion syndrome, which includes memory problems, dizziness, tiredness, sickness and depression. Cerebral concussion is the most common head injury seen in children.
Epidural hematoma (EDH) is a rapidly accumulating hematoma between the dura mater and the cranium. These patients have a history of head trauma with loss of consciousness, then a lucid period, followed by loss of consciousness. Clinical onset occurs over minutes to hours. Many of these injuries are associated with lacerations of the middle meningeal artery. A “lenticular”, or convex, lens-shaped extracerebral hemorrhage will likely be visible on a CT scan of the head. Although death is a potential complication, the prognosis is good when this injury is recognized and treated.
Subdural hematoma occurs when there is tearing of the bridging vein between the cerebral cortex and a draining venous sinus. At times they may be caused by arterial lacerations on the brain surface. Acute subdural hematomas are usually associated with cerebral cortex injury as well and hence the prognosis is not as good as extra dural hematomas. Clinical features depend on the site of injury and severity of injury. Patients may have a history of loss of consciousness but they recover and do not relapse. Clinical onset occurs over hours. A crescent shaped hemorrhage compressing the brain will be noted on CT of the head. Craniotomy and surgical evacuation is required if there is significant pressure effect on the brain.Complications include focal neurologic deficits depending on the site of hematoma and brain injury, increased intra cranial pressure leading to herniation of brain and ischemia due to reduced blood supply and seizures.
Cerebral contusion is bruising of the brain tissue. The majority of contusions occur in the frontal and temporal lobes. Complications may include cerebral edema and transtentorial herniation. The goal of treatment should be to treat the increased intracranial pressure. The prognosis is guarded.
Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of damage.
Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without neurologic deficit.
Patients with concussion may have a history of seconds to minutes unconsciousness, then normal arousal. Disturbance of vision and equilibrium may also occur.
Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.
Symptoms of skull fracture can include:
Because brain injuries can be life threatening, even people with apparently slight injuries, with no noticeable signs or complaints, require close observation. The caretakers of those patients with mild trauma who are released from the hospital are frequently advised to rouse the patient several times during the next 12 to 24 hours to assess for worsening symptoms.
The Glasgow Coma Scale is a tool for measuring degree of unconsciousness and is thus a useful tool for determining severity of injury. The Pediatric Glasgow Coma Scale is used in young children.
Head injury may be associated with a neck injury. Bruises on the back or neck, neck pain, or pain radiating to the arms are signs of cervical spine injury and merit spinal immobilization via application of a cervical collar and possibly a long board.
If the neurological exam is normal this is reassuring, however a serious intra-cranial injury may still be present. If the patient developing a worsening headache, has a seizure, develops one sided weakness, or has persistent vomiting than the patient should be advised to return and a CT should be immediately obtained.
In some cases transient neurological disturbances may occur, lasting minutes to hours. Malignant post traumatic cerebral swelling can develop unexpectedly in stable patients after an injury, as can post traumatic seizures. Recovery in children with neurologic deficits will vary. Children with neurologic deficits who improve daily are more likely to recover, while those who are vegetative for months are less likely to improve. Most patients without deficits have full recovery. However, persons who sustain head trauma resulting in unconsciousness for an hour or more have twice the risk of developing Alzheimer’s disease later in life.
The need for imaging in patients who have suffered a minor head injury is debated. A non-contrast CT of the head should be performed immediately in all those who have suffered a moderate or severe head injury.
Unfortunately, once the brain has been damaged by trauma, there is no quick fix. However, there are some steps that can be taken to prevent secondary damage. If left untreated many patients with head injury will rapidly develop complications which may lead to death or permanent disability. Prompt medical treatment may prevent the worsening of symptoms and lead to a better outcome. Medical treatment should begin at the scene of the trauma. Paramedics will generally immobilize the patient to ensure no further damage to the spine or nervous system, insert an airway to ensure uninterrupted breathing, and perform endotracheal intubation if indicated. One or more IVs will be inserted to maintain perfusion status. In some cases medications may be administered to sedate or paralyze the patient to prevent additional movement which may worsen the brain injury. The patient should be delivered promptly to a hospital with neurosurgical capabilities. The management of brain injury requires the involvement of subspecialists who are generally available only at larger hospitals. Primary treatment involves controlling elevated intracranial pressure. This can include sedation, paralytics, cerebrospinal fluid diversion. Second line alternatives include decompressive craniectomy (Jagannathan et al. found a net 65% favorable outcomes rate in pediatric patients), barbiturate coma, hypertonic saline and hypothermia. Although all of these methods have potential benefits, there has been no randomized study that has shown unequivocal benefit.
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