Abstracts

Absence seizures are defined as paroxysmal alteration of consciousness of sudden onset and end, associated with bursts of bilaterally synchronous spike-and-wave discharges on EEG. The length of the 3 Hz spike and wave pattern is variable, but is usually brief lasting less than 5 seconds.
Absence epilepsy is considered an idiopathic epilepsy, carrying a favorable prognosis. However, little is described about the correlation between the length of spike wave bursts, the clinical manifestations and seizure outcome.
The objectives of this study was to review the clinical manifestations and outcome of patients with prolonged bursts of generalized spike wave complexes (SWC).
We quired our EEG database containing more than 10000 EEG[apos]s for patients with generalized bursts of 3 Hz SWC lasting more than 5 seconds. A retrospective chart review was performed to analyze the clinical manifestations, ancillary tests, treatment and outcome. Patients with slow spike wave complexes were excluded from the study.
A total of 59 patients were identified. There were 31 males and 25 females. Mean age at diagnosis was 9.6 years. Average length of follow up was 4.5 years. EEG background was normal in 75%. Bursts of the SWC lasted 5-10 sec in 66%, 10-20 sec in 29%, and [gt] 20 sec in 6%. Follow up EEG on therapy normalized in only 7%.
Pure absence seizures were seen only in 58%, a combination of absence and generalized tonic clonic seizures were seen in 21% and pure generalized tonic clonic seizures were seen in 8%. Additional seizure types were seen in the remainder. Normal development was seen in 60%, mostly in the pure absence seizure group. Mild developmental delay was seen in 17%, moderate in 19%, and severe in 4%. Neurological examination was abnormal in 31%. The percentage of patients maintained on the initial therapy was similar in all groups (55-58%). 22-30% required therapy change to a second AED and the remainder of patients required additional AED changes. Patients with absence seizures became seizure free in 38%, had a significant ([gt]50%) reduction in their seizures in 24%, and had poorly controlled seizures in 38%. The outcome for patients with generalized tonic clonic seizures was 41%, 29%, and 30% respectively.
Prolonged bursts of SWC ([gt] 5 secs.) on EEG were associated with a relatively severe clinical syndrome as compared to patients with typical benign absence seizures. These patients had an increase incidence of generalized tonic clonic seizures (29%), developemental delay (40%) and an abnormal neurological examination (31%).
Seizure freedom was achieved in less than 40%. Follow up EEG revealed persistence of the EEG SWC abnormalities in most of the cases.
[Supported by: Department of Neurology, Children[apos]s Hospital of Buffalo (Internal funding). ]