Etiology of Acute Childhood Encephalitis at The Hospital for Sick Children, Toronto, 1994–1995

Abstract

Of 145 patients admitted to our hospital because of encephalitis-like illness, 50 patients hospitalized for > or =72 hours underwent standardized microbiological investigations. A confirmed or probable etiologic agent was identified in 20 cases (40%), including Mycoplasma pneumoniae (9 cases). M. pneumoniae and enterovirus (2), herpes simplex virus (4), Epstein-Barr virus (1), human herpes-virus 6 (HHV-6) (1), HHV-6 and influenza virus type A (1), influenza virus type A (1), and Powassan virus (1). In 13 cases (26%), a possible pathogen was identified, including M. pneumoniae in nine cases. Presenting features included fever (80% of patients), seizures (78%), focal neurological findings (78%), and decreased consciousness (47%). The frequency of findings at the time of admission vs. later in hospitalization was as follows: pleocytosis, 59% vs. 63%; electroencephalogram abnormalities, 87% vs. 96%; and neuroimaging abnormalities, 37% vs. 69%, respectively. 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% (severe, 6; mild, 2); mental status changes, 14% (7); visual defects, 8% (4); and hearing impairment, 2% (1).

Infectious and Autoantibody-Associated Encephalitis: Clinical Features and Long-term Outcome

“…Immunotherapy has only recently become established in the treatment of autoantibody-associated encephalitis (other than ADEM), 3 and prospective studies are needed to determine the benefit of immunotherapy in patients with encephalitis irrespective of whether an autoantibody is detected. The percentage of unknown encephalitis (28%) in this study is the lowest among substantial pediatric cohorts, [6][7][8]40,41 but it represents an important subgroup that is comparable in size to the prospective UK cohort in adults and children. 5 There were no distinguishing clinical or radiologic characteristics of the unknown subgroup, mainly because of the likely heterogenous etiologies.…”

“…Although by definition ADEM is an encephalomyelitis, it is notable that many previous encephalitis cohorts do not include ADEM but generally focus on infectious encephalitis alone. [6][7][8]21 NMDAR-Ab encephalitis was diagnosed in 6% of patients, who had typical clinical features of the disease, with dominant movement, psychiatric, sleep, speech, and autonomic features. The number could be an underestimate, because serum testing was performed on only 103 out of 129 (81%) of the patients without ADEM.…”

“…5 However, most of the previous larger studies of encephalitis in children were undertaken before the advent of neuronal autoantibody testing. [6][7][8] We studied clinical and radiologic features, serum autoantibodies in acute archived samples, and longterm outcomes in a large retrospective cohort of pediatric encephalitis from a single center. …”

Delayed Primary HHV-7 Infection and Neurologic Disease

“…Encephalitis cases were identified from the hospital' s Encephalitis Registry, which has been in place since 1994 and for which inclusion criteria and investigations have previously been described. 11,12 All other cases were identified from the hospital' s Microbiology Laboratory database. Clinical data were extracted from the hospital charts.…”

Long-term Motor and Cognitive Outcome of Acute Encephalitis

“…2 Viruses are the most frequently diagnosed infectious cause of encephalitis; bacteria, fungi, and parasites are less common. 3,4 The frequency and distribution of viruses or other infectious agents causing encephalitis vary according to geographical region. In Asia, the major identified cause of acute encephalitis is the Japanese encephalitis virus.…”