Sequelae of Western Equine and Other Arthropod‐Borne Encephalitides

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Abstract
The clinical features of sequelae to the North American arthropod-borne encephalitides were presented on the basis of a review of the literature. Noteworthy was the greater incidence (13.5%) of sequelae to western equine encephalitis (WEE) as contrasted to a lower ratio in St. Louis encephalitis, and the increased frequency and severity of sequelae in infants following WEE infection. The pathoanatomic features in a case showing sequelae were reported, this apparently being the 1st such report in a serologically-confirmed case. In a 5-year-old boy showing severe intellectual and milder neurologic residua following an attack of WEE at 4 weeks of age, extensive glial scars confined to the subcortical cerebral white matter, the cortex by extension of the white matter lesions, and to the thalamus were found. Within these scars an unusual deposition of "calcifications" had occurred. When compared to the findings usually observed in the acute stage of the disease, in distribution these lesions appeared to be related to, and the residua of, the neerotic rather than the inflammatory component of the acute disease. A unique finding was the presence of such inflammatory activity as microglial nodes and perivascular lymphocytic cuffing. These lay adjacent to the chronic lesions. It was suggested that this might well represent evidence of persistent virus activity.