Interictal epileptiform activity Fixation-off epileptiform discharges 2021-03-30T15:42:07Z FOS occurs mainly in children who have non-acquired focal epilepsies with occipital epileptiform discharges and in people with generalized epilepsies with photosensitivity such as eyelid myoclonia with absences. It has been observed in people with epilepsies due to structural brain lesions and people without epilepsy who have posterior epileptiform discharges. Fixation-off sensitivity Fixation off sensitivity (FOS) is characterized by posterior or generalized epileptiform discharges that consistently occur with conditions that eliminate central vision, such as closed eyes, complete darkness, modified Ganzfeld stimulation (using a large white surface without visual cues), and Frenzel lenses. The FOS electroencephalogram (EEG) pattern usually consists of spikes/polyspikes and waves localized in occipital regions (bilateral or unilateral) or generalized discharges. It is usually inhibited by fixation of gaze, observing patterns, or intermittent photic stimulation (e.g., flashing light or patterns used as stimuli during the recording of the EEG).