La crosse encephalitis in children.

Background: La Crosse encephalitis is a mosquito-borne disease that can be mistaken for herpes simplex encephalitis. It has been reported in 28 states but may be underrecognized. Methods: We investigated the manifestations and clinical course of La Cross e encephalitis in 127 patients hospitalized from 1987 through 1996. The dia gnosis was established by serologic testing for IgM and IgG antibodies to L a Crosse virus. Data were collected by chart review. Results: Most of the patients were school-aged children (mean [+/-SD] age, 7.8+/-3.5 years; range, 0.5 to 15.0). Symptoms included headache, fever, an d vomiting (each in 70 percent or more of the patients), seizures (in 46 pe rcent), and disorientation (in 42 percent). Thirteen percent had aseptic me ningitis. Hyponatremia developed in 21 percent, and there were signs of inc reased intracranial pressure in 13 percent. Six patients, including three w ith cerebral herniation, underwent intracranial-pressure monitoring. The 13 patients (11 percent) whose condition deteriorated in the hospital had dec reases in serum sodium levels (P=0.007) and increases in body temperature ( P=0.003) at the time of deterioration. At admission, these patients more of ten had a history of vomiting (P=0.047) and a score of 12 or lower on the G lasgow Coma Scale (P=0.02) than the others; a trend toward a greater preval ence of seizures at admission was also evident in this group (P=0.07). All the patients survived, but 15 of them (12 percent) had neurologic deficits at discharge. Follow-up assessments, performed in 28 children, suggested an increase in cognitive and behavioral deficits 10 to 18 months after the ep isode of encephalitis. Conclusions: La Crosse virus infection should be considered in children who present with aseptic meningitis or encephalitis. Hyponatremia and increasi ng body temperature may be related to clinical deterioration. (N Engl J Med 2001;344:801-7.) Copyright (C) 2001 Massachusetts Medical Society.