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 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.