St Louis encephalitis - A review of 11 cases in a 1995 Dallas, Tex, epidemic

Objective: To update some of the clinical features of St Louis encephalitis (SLE), a common arboviral infection that occurs in epidemic patterns in th e southcentral and midwestern United States. Methods: Eleven patients with SLE from a 1995 epidemic in Dallas, Tex, were studied clinically, radiologically, neurophysiologically, and neuropatholo gically (in 1 case). Results: The electroencephalograms and magnetic resonance imaging (MRI) sca ns of our patients revealed features that have received little attention in previous studies. Of the 9 patients who were examined with electroencephal ography, all 9 had seizures or other abnormalities, and 1 had nonconvulsive status epilepticus. Two of 6 patients who had MRIs showed substantia nigra edema. Finally, 2 (18%) of our patients had coinfection with the human imm unodeficiency virus. Conclusions: The MRI findings of substantia nigra edema in patients with SL E have not been previously reported. Nonconvulsive status epilepticus can o ccur in patients with SLE and should be considered in patients with prolong ed encephalopathy. Finally, human immunodeficiency virus coinfection may be a risk factor for symptomatic SLE infection.