ABSTRACT
Encephalitis is usually due to a viral infection of the brain and is most often of viral etiology. Encephalitis presents as encephalopathy, i.e., with mental confusion. Meningitis is characterized by meningeal irritation and nuchal rigidity without mental confusion and is usually due to bacteria. Viral encephalitis is characterized by mental confusion, but nuchal rigidity is not a feature of the infection. Some organisms, i.e., Mycoplasma pneumoniae, Listeria monocytogenes, may present as meningoencephalitis or encephalitis. Patients with meningoencephalitis present with both mental confusion and nuchal rigidity. Patients are usually admitted to the critical care unit (CCU) with the diagnosis of encephalitis and some become encephalopathic while in the CCU. The main diagnostic problem in the CCU is to differentiate noninfectious from infectious causes as well as to identify the treatable causes of acute encephalopathy (1-4).
