The primary goal in the acute management of severe traumatic brain injury (TBI) is to prevent secondary brain damage caused by a sharp rise of intracranial pressure (ICP). Trauma related etiologies of increased ICP include hemorrhagic contusions, epidural hematomas, subdural hematomas, and diffuse axonal injury.
Approximately 10-15% of patients who have suffered a severe TBI have sustained elevations in ICP that will not respond to medication management. This produces an unsustainable elevation in ICP that will impair blood flow to the brain, decrease function, and potentially lead to brain herniation and death. Sustained ICP will cause secondary brain damage beyond what was caused by the original injury to the brain by interfering with cerebral oxygen supply and cerebral blood flow.
A decompressive craniectomy (DC) results in the lowering the ICP to a safe level in 80% of patients by removing a section of skull that will allow for the brain to expand rather than to be compressed by the increasing ICP in the closed cranial vault that composes the skull. In addition, a DC can prevent imminent brain herniation in a scenario where the increased ICP is causing a shift of the brain and brainstem down into the spinal canal, which ultimately causes death.
Outcome studies are by no means conclusive that providing a DC provides for a superior outcome but there is evidence suggesting a decreased mortality and increased proportion of patients that achieve a good functional outcome with this intervention.
As with any medical or surgical intervention there are risks versus benefits involved with a DC. Complications include the potential for hemorrhagic cerebral contusion expansion, subdural hygromas, infection, post-traumatic hydrocephalus, paradoxical brain herniation, and the sinking skin flap syndrome referred in the literature as the Syndrome of the Trephined.
Studies are mixed regarding the potential for hemorrhagic cerebral contusion to increase in size following a DC. Expansion is believed to be related to the increased ICP that will prevent further bleeding in the hemorrhagic contusion by applying pressure to the bleeding area and by providing a DC the bleeding will resume or continue. It is also unclear if the expansion of a cerebral contusion following a DC clinically leads to a worse outcome. Regardless of the above serial CT scans beginning 24 hours after a DC are necessary to follow for clinically significant cerebral contusion expansion.
Subdural hygromas is a fluid collection in the subdural space that may develop in up to 50% of patients who undergo at DC. Studies indicate that a vast majority will resolve within four months without surgery. Hygromas that develop on the side opposite of the DC should be followed closely since opposite side hygromas tend to be the ones with the greatest tendency to cause neurological compromise.
Post-traumatic hydrocephalus is also associated with decompressive craniectomies. Diagnosis is based on neurological compromise with imaging studies consistent with increased size of the cerebral ventricles. Difficult clinical decision in the DC patient regarding necessary interventions may include shunt placement, cranioplasty (surgical replacement of the skull fragment), and shunt placement following cranioplasty.
The Syndrome of the Trephined is delayed neurological decompensation related to atmospheric pressure effects on the brain through the skull defect. Symptoms may include headaches, dizziness, decreased concentration, mood disturbances, and potentially motor defects. Early treatment with an early cranioplasty is indicated to treat this reversible complication.
Academic Physician Life Care Planners and catastrophic case managers must be involved early in the clinical recovery of a TBI patient who is post-operative from a DC. Rehabilitation must be provided at a facility with similar capabilities as a TBI Model Systems Hospital with Neurosurgeons and Physical Medicine and Rehabilitation specialist working closely together to timely diagnose and intervene when complications arise. Patients requiring a DC and subsequent cranioplasty will require lifetime imaging studies and physician follow up care monitoring for hydrocephalus.