Objective: To test the hypothesis that absence seizures can evolve to generalized tonic-clonic seizures, we documented electro-clinical features of this novel seizure type.

Methods: In four large video-EEG databases, we identified recordings of seizures starting with impaired awareness and that, without returning to baseline interictal state, evolved to generalized tonic-clonic seizures. We extracted the detailed semiological and electrographical characteristics of these seizures, and we documented the clinical background, diagnoses and therapeutic responses in these patients.

Results: We identified 12 seizures from 12 patients, fulfilling the inclusion criteria. All seizures started with a period of impaired awareness and bursts of generalized spike or polyspike and slow-wave discharges – the hallmark of absence seizures. Without returning to baseline, the nonmotor (absence) phase was followed by tonic-clonic convulsions. We coined this novel generalized seizure type absence-to-bilateral-tonic-clonic seizure. Most patients had idiopathic generalized epilepsies, though with a high incidence of unusual features and poor therapeutic response.

Conclusions: Absence-to-bilateral-tonic-clonic seizures are a novel generalized seizure type. Clinicians should be aware of this seizure for correctly diagnosing the patients. This novel seizure type may further elucidate generalized ictogenesis.

Instructions:

The .exe-files are self-extracting files that installs an EEG-reader that can play video synchronized with EEG. They can be opened using a Microsoft Windows operating system, by double-clicking on the file. This will open a video-EEG reader with the video files synchronized with the EEG.