Abstracts

The 1997[ndash]2002 influenza epidemics in Japan were markedly neurovirulent, and many children died or had neurological sequelae of influenza-associated encephalitis or encephalopathy. We examined serial electroencephalographic changes and epilepsy as sequelae of influenza-associated encephalitis or encephalopathy. We experienced 21 patients with influenza-associated encephalitis or encephalopathy during the 1997[ndash]2002 influenza seasons. Five patients died, nine had residual neurological sequelae and the other seven completely recovered. Nine patients with sequelae of influenza-associated encephalitis or encephalopathy were included in this study. Their clinical course and serial electroencephalographic findings through 2004 were studied. In the acute phase, all patients showed frequent seizures. In convalescent phase, epileptic seizures were observed in five patients, two with symptomatic localization-related epilepsy and three with symptomatic generalized epilepsy. At the end of 2004, three patients suffered from epilepsy. Seven patients were administered anti-epileptic drugs. Their developmental quotient ranged from 22 to 62. Electroencehalography revealed high-voltage slow-waves in the acute phase in all patients, and two showed periodic discharges. One to twelve months later, focal spikes developed in seven patients, and 4 to 18 months later, diffuse polyspikes or spike and wave developed. Subsequently, epileptic abnormality disappeared in two patients one to two years later. However, focal spikes reappeared in these two patients. Serial electroencephalographic changes were common in our patients and might be a characteristic finding following influenza-associated encephalitis or encephalopathy. It is also important to examine electroencephalograms to detect any neurophysiological sequelae of influenza-associated encephalitis or encephalopathy, even if there are no epileptic seizures.