Significance of spontaneous epileptiform abnormalities associated with a photoparoxysmal response

Spontaneous epileptiform abnormalities (SEAs) are reported to occur in up to 65% of patients with a photoparoxysmal response (PPR). Although the PPR is usually assumed to indicate primary generalized epilepsy, the clinical significance of associated SEAs is not known. We conducted the first study designed to correlate seizure classification with type of SEA in photosensitive patients. We examined seizure classifications and SEAs in 115 consecutive patients who had a PPR. A PPR was the only epileptiform abnormality in 47 patients (41%). Twenty-seven patients (24%) had focal SEAs and 41 (36%) had only generalized SEAs. Seventeen patients (15%) had partial seizures and 40 (35%) had only generalized seizures. Seizure classification was strongly associated with type of SEA (p < 0.0001). Patients with focal SEAs tended to have partial seizures, while patients with generalized SEAs tended to have only generalized tonic-clonic or absence seizures. Also, the presence of SEAs was significantly associated with a history of seizures (p < 0.0001), compared with patients who had a PPR but no SEAs. Although the PPR is often presumed to signify primary generalized epilepsy, most patients with a PPR and focal SEAs have partial seizures.