Purpose: The individual electroclinical patterns--tonic seizures with generalized paroxysmal fast activity (GPFA, activity >13 Hz), and absence seizures with generalized slow spike-and-wave activity (GSS&W, <3 Hz)--have been extensively described in the literature. However, only passing reference was made to the pattern of GPFA followed by GSS&W. In addition, these descriptions were formulated in the pre-EMU (Epilepsy Monitoring Unit) era, without benefit of video/clinical correlation. We now characterize this underrecognized seizure type.
Methods: We retrospectively reviewed the data from eight patients with seizures that demonstrated this stereotyped EEG and clinical pattern.
Results: We identified eight patients (six female patients; age 6-29 years; age at seizure onset, neonate to 10 years) who were evaluated at the Columbia University Epilepsy Monitoring Units between 1993 and 2002. All eight had an International League Against Epilepsy (ILAE) diagnosis of symptomatic generalized epilepsy, with six of eight manifesting multiple seizure types, six of eight with mild static encephalopathy, and two with normal cognition. A total of 29 seizures of this pattern was recorded; 26 of 29 seizures demonstrated GPFA (frequency between 14 and 30 Hz, lasting 2-8 s) followed by GSS&W (frequency range between 1 and 2 Hz, lasting 3-50 s). The predominant clinical correlate was bilateral tonic activity followed by a period of inattentiveness. In general, these seizures were differentiated from the patient's typical tonic seizures by this protracted period of impaired attentiveness.
Conclusions: We describe a heretofore underrecognized and poorly characterized seizure type in patients with symptomatic generalized epilepsy, which we have termed tonic-absence seizures. Clinically and electrographically, this consists of a tonic seizure with GPFA followed by an absence seizure with GSS&W.