Absence-to-bilateral-tonic-clonic seizure: A generalized seizure type.

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 4 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. 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.