Cortical myoclonic tremor induced by fixation-off sensitivity An unusual cause of insomnia

Fixation-off sensitivity (FOS) refers to seizures or EEG abnormalities elicited by the elimination of central vision/fixation, even in the presence of light. Typically, a paroxysmal discharge occurs within 1–3 seconds of eye closure, persists throughout the eye-closed state, and disappears immediately on eye opening. FOS occurs mainly in childhood occipital epilepsies.1 It has also been reported in generalized and focal epilepsies of structural/unknown etiology, eyelid myoclonia with absences, and rarely in non-epileptic individuals. We describe a patient with FOS associated with cortical myoclonic tremor (CMT) so intense and severe at wake–sleep transition to cause sleep-onset insomnia as the main complaint.