ETIOLOGY OF ACUTE CHILDHOOD ENCEPHALITIS AT THE HOSPITAL-FOR-SICK-CHILDREN, TORONTO, 1994-1995

Of 145 patients admitted to our hospital because of encephalitis-like illness, 50 patients hospitalized for greater than or equal to 72 hour s underwent standardized microbiological investigations, A confirmed o r probable etiologic agent was identified in 20 cases ( 40%), includin g Mycoplasma pneumoniae (9 cases), ill. pneumoniae and enterovirus (2) , herpes simplex virus (4), Epstein-Barr virus (1), human herpesvirus 6 (HHV-6) (1), HHV-6 and influenza virus type A (1), influenza virus t ype A(1), and Powassan virus (1), In 13 cases (26%), a possible pathog en was identified, including M. pneumoniae in nine cases. Presenting f eatures included fever (80% of patients), seizures (78%), focal neurol ogical findings (78%), and decreased consciousness (47%), The frequenc y of findings at the time of admission vs, later in hospitalization wa s as follows: pleocytosis, 59% vs, 63%; electroencephalogram abnormali ties, 87% vs. 96%; and neuroimaging abnormalities, 37% vs. 69%, respec tively, The outcomes at the time of discharge were as follows: normal results of physical examination, 32% (16) of the patients; death, 2% ( 1); motor difficulties, 26% (13); global neurological deficits, 16% (s evere, 6; mild, 2); mental status changes, 14% (7); visual defects, 8% (4); and hearing impairment, 2% (1).