Infectious lesions of the brain stem.

Infectious lesions of the brain stem are rare and include primarily abscess and encephalitis. The most common etiologic agents for abscess formation are Streptococcus sp., Staphylococcus sp., and M. tuberculosis. Encephalitis is associated most often with L. monocytogenes and herpes simplex virus infection. Classical brain stem syndromes are uncommon with brain stem infections, and CSF obstruction can be seen with neurocysticercosis. The diagnosis of these lesions has been greatly aided by CT and MR imaging. Microsurgery and stereotaxis are both appropriate techniques for the treatment of brain stem abscess that establish a diagnosis, identify the causative agent, and relieve mass effect on important neural structures. Symptoms of hydrocephalus should be treated with temporary or permanent CSF diversion. Viral involvement of the brain stem is usually self-limited, and improved antimicrobial therapy has contributed to a decrease in the morbidity and mortality of bacterial and parasitic infections. Although once believed to be uniformly fatal, infections of the brain stem have now been successfully treated for more than a decade.