Idiopathic photosensitive occipital lobe epilepsy is an idiopathic epilepsy syndrome with visually induced seizures that usually begins around puberty. Ictal manifestations are described as bright, colorful, or multicolored rings or spots in the periphery of the visual field. Some patients report ictal blindness or severe blurring of vision. Visual phenomena are often followed by a versive phase, with head and eye deviation, and when the seizures progress, the most frequent ictal sequence is epigastric discomfort, unresponsiveness, and vomiting. Single or repeated seizures may occur without a previous history of spontaneous seizures while playing video games or watching television. Developmental delay and learning difficulty may be seen in some patients. Visually triggered seizures are associated with the inability of the visual cortex to process afferent inputs of high luminance and contrast through the normal mechanisms of cortical gain control. Critical neuronal mass activation in the occipital cortex, propagation of the abnormal discharges along the cortico-cortical or cortico-subcortical pathways, and the influence of specific epilepsy genes predisposing to this phenotype were also found to be important contributors.
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• Idiopathic photosensitive occipital lobe epilepsy is typical of, although not exclusive to, adolescence.
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• Misdiagnosis with migraine is frequent.
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• Differentials include Lafora body disease, symptomatic occipital epilepsy with photosensitivity, and other idiopathic epilepsies with photosensitivity.
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• Seizure control is related more to avoidance of precipitants than to treatment.
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• Overall prognosis is generally good.
Historical note and terminology
Reflex epilepsies are characterized by specific modes of seizure precipitation and have been incorporated in the new definition of epilepsy (14; 20; 24). The most frequent forms of reflex epilepsies are the photosensitive epilepsies, in which seizures are provoked by environmental light stimulation. Gastaut and colleagues provided the first evidence of the electroclinical correlates of intermittent photic stimulation in photosensitive patients stimulated with a flash lamp (27). Numerous studies have since clarified many characteristics of visually induced seizures (50; 06; 40; 38; 84). Visually-induced seizures are frequently seen as one element of idiopathic generalized epilepsies also featuring other seizure types (14; 20; 31; 38; 84) or as the only type of seizures in 'pure' photosensitive epilepsies. Most often they appear to be generalized, but in up to 17% of photosensitive patients, they may originate from the occipital lobe (29; 84). Although photic-induced occipital seizures are associated with a brain lesion in some patients, the more typical pattern of recurrent photosensitive occipital seizures is usually observed in the context of idiopathic epilepsy, with onset around puberty (73; 63; 30; 29). The clinical and EEG characteristics indicating an idiopathic localization-related epilepsy were not always specifically detailed, especially in the early reports (16; 35; 49; 23; 18; 03; 45; 11; 47; 63; 22; 30; 28; 71; 85), where generalized features received much emphasis. Idiopathic photosensitive occipital lobe epilepsy may be defined as an idiopathic focal (local, localization-related, partial) epilepsy with age-related onset and specific mode of precipitation. The syndrome has been recognized by the ILAE task force on classification and terminology and should be included in the self-limited focal epilepsies according to the 2017 ILAE classification (20; 66).