Duration of transient amnesia correlates with cognitive outcome in acute encephalitis

Temporary periods of amnesia are encountered in acute encephalitides. We investigated the association between transient encephalitic amnesia (TENA) and outcome in 60 patients. Twenty-six patients had TENA lasting < or = 1 day (short TENA), 17 had TENA lasting 2-7 days, and 17 had TENA for > 7 days (long TENA). The long TENA group had more neuropsychological impairment, larger brain lesions, and more difficulty in daily activities than the short TENA group. The findings were not explained by the number of epileptic seizures, delay of acyclovir medication, or the aetiology of encephalitis. TENA is a useful new clinical tool in predicting the outcome of acute encephalitis and selecting patients who are in need of detailed neuropsychological evaluation.