Abstracts

Influenza encephalopathy is associated with acute seizures, significant mortality and high risk for long term neurological sequelae. Little information exists about EEG patterns in this condition or their relationship to prognosis. EEG findings and seizure characteristics in children treated for influenza encephalopathy were reviewed to determine association with clinical course and outcome., In the past 3 years 6 children with influenza encephalopathy were treated at UT Southwestern Medical Center/Children[apos]s Medical Center, Dallas. Medical records were reviewed to identify the incidence and clinical characteristics of seizures, neuroimaging findings and EEG abnormalities. When possible information regarding neurological outcome was also obtained., 3 boys and 3 girls with influenza encephalopathy were identified. Ages ranged from 6 months to 9 years. All had clinical seizures within 4 days after onset of influenza symptoms. The oldest child was on immunosuppressive steroid therapy which may explain her severe course and fatal outcome. She presented with hallucinations, hepatic failure and hypotensive shock and developed seizures on the second hospital day. The other 5 children all presented with seizures at the time of hospital admission, 4 with status epilepticus, and 1 with 3 seizures within 24 hours. In 2 cases the seizures had focal features. Of the 5 survivors, 2 had no evident disability, 1 had transient speech and cognitive slowing which resolved within 6 weeks, and 2 had significant disability with loss of speech and ambulation and were transferred to a rehabilitation facility. EEG was performed within 2 days of hospital admission in all cases. All EEGs showed abnormal slowing of the background activity. The 3 cases with favorable outcome had either sleep spindles or an awake posterior dominant rhythm. The 3 cases with poor outcome lacked these features and showed diffuse delta activity with poor reactivity to external stimuli. None of the acute EEGs had epileptiform findings. Only the 2 survivors with poor outcomes had recurrent seizures and required chronic antiepileptic therapy. Neuroimaging showed basal ganglia infarction in 4 cases (including 1 with transient disability but favorable outcome), diffuse atrophy in 1 and was normal in 2 (both with good outcome)., Influenza encephalopathy commonly presents with seizures or status epilepticus, but epileptiform activity is not present on EEGs performed acutely. The presence of any normal awake or sleep EEG patterns was associated with a favorable outcome in our series, even when basal ganglia infarction was seen on MRI. In the absence of these features outcome was poor with significant neurological disability and epilepsy in surviving children. These finding suggest that EEG may be helpful in determining prognosis, especially when combined with neuroimaging results.,