The evolution and disappearance of photosensitivity (PS) was studied long-term in 42 patients (17 males, 25 females; mean age at onset 6 years 9 months, range 5 to 12 years) with electroencephalographic evidence of photosensitive epilepsy at University of Chieti, San Valentino Hospital, and Brindisi Hospital, Italy. Valproate (VPA) monotherapy was begun after the second seizure in 36 patients, VPA with carbamazepine or lamotrigine in 4, and stimuli avoidance but no drugs in 2. Mean duration of follow-up was 8 years 1 month, and the mean age at end of follow-up was 15 years 2 months. At end of follow-up, photoparoxysmal responses (PPRs) were present in 25 and had disappeared in 15. Of 31 (75%) responding to antiepileptic drugs (AEDs), 19 had persistent PS and 12 were PS free. Photosensitive epilepsy has a good prognosis for seizure control, independent of persistence or disappearance of PS. Response to AEDs is not dependent on disappearance of PS. PS is probably not linked to a genetic susceptibility to epilepsy. [1]

COMMENT. Photosensitive epilepsy is defined as recurrent seizures in photosensitive patients, with EEG-PPRs in response to intermittent photic stimulation. According to several references cited by the authors, photosensitivity (PS) occurs in 2 to 20% of patients with epilepsy, and may also be present in non-epileptic individuals. PS can occur in any type of epileptic disorder and is not a specific epileptic syndrome. Pure PS epilepsy is characterized by generalized paroxysmal epileptiform discharges exclusively provoked by flicker, usually in adolescence, predominantly females. PS epilepsy has a good prognosis, independent of disappearance or persistence of PS

Short-term outcome of Pokemon phenomenon and TV-induced seizures was determined at Nagoya University, Japan [2]. Of 103 patients with epileptic seizures during the TV program, 25 (24%) had unprovoked seizures before the incident (Epilepsy group), and 78 (76%) did not (Non-epilepsy group). Twenty-three (22%) had seizures after the incident, 15 visually induced. Patients in the Epilepsy group had more seizure recurrences (both unprovoked or visually induced) than the Non-epilepsy group (56% vs 9%; p<0.0001). PPRs on EEG were present in 45 (46%) patients, and spontaneous epileptiform discharges in 49 (50%). PPRs were not correlated with recurrence of seizures, whereas spontaneous epileptiform discharges were significantly correlated (34% vs 8%; p<0.01). Of patients with seizures during the TV incident, 70 (68%) had no seizures before or during the 3 year follow-up. Color changes, specifically red, rather than luminance was found to be the critical seizure-inducing factor in the TV scene, prompting color restrictions in TV cartoon programs in Japan.

For reports and commentaries on visually-induced seizures, including video game seizures and pattern sensitive seizures, see Progress in Pediatric Neurology III, PNB Publishers, 1997;64-67.