Primary generalized seizure disorder: correlation of epileptiform discharges with seizure frequency

The role of routine follow-up EEG in assessment of severity of a seizure disorder is not known. This retrospective chart review study of patients with primary generalized seizure disorders explored the relation between parameters of epileptiform discharge bursts on EEG and number of seizures experienced in the preceding months. Eighty-seven such patients were found, each with one to seven EEGs and corresponding clinical records, comprising a total of 201 clinicoelectrographic epochs. The 56 chronically attending patients (more than two attendances) differed from the 31 nonchronic attenders in receiving more antiepileptic drugs (AEDs) and having fewer EEG polyspikes; otherwise, the two groups were similar and were analyzed together. We noted a strong relation between number and maximum length of epileptiform bursts in the resting EEG record and number of absence seizures reported in the months preceding the EEG. Age did not affect this relation. After stepdown regression analysis, only the maximum length of epileptiform bursts remained significantly related to the reported number of absence seizures. These findings may prove useful in assessing clinical progress, e.g., in patients whose ability to estimate numbers of attacks is suspect. Neither number nor maximum length of epileptiform bursts in the resting EEG record had a significant relation with the number of generalized tonic-clonic seizures. Presence of polyspikes on resting or "activated" EEG had no added predictive value. The presence of epileptiform bursts after activation by sleep, hyperventilation, or photic stimulation was not associated with an increased likelihood of having had seizures.