• Meningitis is inflammation of the meningeal membranes of the brain and spinal cord. Encephalitis is inflammation of the brain parenchyma with or without inflammation of the meninges. Cerebral perfusion is a function of arterial pressure and intracranial pressure (i.e., cerebral perfusion pressure = mean arterial pressure – intracranial pressure). Hypoperfusion results from cerebral edema and increased intracranial pressure (ICP). Meningitis is a life-threatening condition with up to 30% mortality and high risk of long-term neurological complications.

The differential diagnosis for meningitis and encephalitis includes subarachnoid hemorrhage, cerebral venous thrombosis, metabolic/toxic encephalopathy and other infections not involving the central nervous system (CNS).