Encephalitis in the ICU setting

SummaryAcute encephalitis, also known as meningo-encephalitis and encephalomyelitis, constitutes a medical emergency. While the presence of focal neurological signs and seizures may differentiate it from encephalopathy, the involvement of other sites, such as the meninges (brain tissue) and spinal cord (myelitis) may make clinical differentiation difficult.It is relatively common with a broad spectrum of presentation which can include confusion, seizures, coma, respiratory depression, cranial nerve palsies and paralysis. The viral nature of the illness provides a wide range of associated symptoms and signs such as parotitis, herpangia, pleurodynia, myopericarditis, lymphadenopathy and hepatosplenomegally.During the acute event there are many possible associated problems due to the loss of consciousness, the raised intracranial pressure (ICP), or both. Respiratory problems include upper airway obstruction, pulmonary aspiration and central respiratory depression while general neurological manifestations include hyperpyrexia, convulsions and rapidly progressive cerebral oedema.HSV is the most common fatal sporadic encephalitis in humans but VZV, EBV, mumps, measles and entero-viruses are also responsible for of acute viral encephalitis in immuno-competent patients. TB, Rickettsial diseases and human African trypanosomiasis are important non-viral causes of meningo-encephalitis.The mainstay of treatment is supportive. Early institution of acyclovir chemotherapy has substantially improved the clinical outcome of HSV-encephalitis. It is, as yet unknown, whether the newer antiviral therapies (ribavarin and pleoconaril) will have an impact on the clinical outcome of non-herpes viral encephalitis. Immunisation may prevent certain types of non-herpes encephalitis (e.g. Measels, Mumps, Rubella, Rabies and Japanese encephalitis). Vector control and environmental sanitation are important in the prevention of large outbreaks of arboviral encephalitis (e.g. Japanese encephalitis).As a consequence of both the complications and the underlying disease, mortality and morbidity are high, and there is also a high incidence of long-term sequelae.