Photosensitive absence seizures: a rare endophenotype with clinical and prognostic implications.

OBJECTIVE: Photosensitivity is a well-recognized phenomenon in epilepsy, yet its association with absence seizures (AS) is rarely described and poorly understood. This study aims to characterize the clinical and electrophysiological features of patients exhibiting AS induced by photic stimulation (PS) and evaluate their prognostic implications. METHODS: We retrospectively analyzed 48,000 EEG recordings from a tertiary epilepsy center (2009-2025). Patients were included if they experienced at least one electroclinical AS during PS. Their clinical and electrophysiological findings were evaluated. RESULTS: Data from 22 patients (16 females, 6 males) were analyzed. Median age was 21 years (IQR: 16-35), and median seizure onset age was 9 years (IQR: 6.5-13). Childhood absence epilepsy (CAE, 31.8%) was the most common epilepsy syndrome, followed by epilepsy with eyelid myoclonia (22.7%), juvenile myoclonic epilepsy (22.7%). Of the patients, 64% were drug-resistant, and only one of the CAE patients achieved remissions. 50% had a positive family history of epilepsy. During PS at 5-45 frequencies, the EEG showed multispike-wave discharges in the 3-3.5 Hz range. CONCLUSION: Photosensitive AS are rare but form a distinct endophenotype within idiopathic/genetic generalized epilepsies. Our findings indicate an unexpectedly poor prognosis, marked by significant drug resistance and low remission rates, even in CAE. SIGNIFICANCE: Describing the characteristics of photosensitive AS and their prognostic implications.