Head trauma can occur from numerous causes. The most common causes are being hit by a car or from an animal bite.
Traumatic brain injury can be divided into two main categories:
- Primary brain injury, which occurs immediately upon impact and consists of contusion, laceration, diffuse axonal injury and vascular injury from hemorrhage, vasogenic edema, and decreased perfusion. Primary brain injury cannot be prevented or ameliorated with treatment. The degree of brain injury is correlated with the amount of brain deformation rather than the amount of force per unit of area. The cerebral cortex is more vulnerable than the brainstem to the forces of acceleration/deceleration.
- Secondary brain injury consists of a cascade of metabolic changes that rapidly follow primary brain injury, including ATP depletion, increased intracellular sodium and calcium, cytotoxic (intracellular) edema, neuronal depolarization, increased release of excitatory neurotransmitters, oxygen free radical production, increased cytokine production, nitric oxide accumulation, activation of arachidonic acid, kinin, complement, coagulation and fibrinolytic cascades, and lactic acidosis. Secondary brain injury causes increased intracranial pressure, which is the major cause of death in head trauma patients. Hypotension, hypoxemia, and ischemia perpetuate secondary brain injury and increase lactic acid accumulation, which further damages the brain. Prompt preventive measures to avoid hypoxia, hypercarbia, hypotension, and hypovolemia can be effective in minimizing secondary brain injury by maintaining cerebral perfusion pressure.
Head trauma patients are usually presented with some degree of altered consciousness. Motor deficits and cranial nerve alterations may or may not be present. The Modified Glasgow Coma Scale is useful in assessing the degree of brain injury and determining prognosis based on a combination of clinical signs.
Medical treatment consists of medications to reduce swelling and general supportive measures. Some case may require surgery, especially if the skull is fracture and displaced significantly.
The prognosis depends on the severity of the clinical signs and how they respond to initial treatment.