Eye-Closed Sensitivity in a Patient with Idiopathic Generalized Epilepsy

In certain epilepsy syndromes, uncommon electroencephalogram (EEG) patterns linked to oculo-visual responses may yield valuable diagnostic clues. A 16-year-old boy presented with a history of generalized tonic-clonic seizures spanning 4 years. Birth and developmental milestones were normal prior to seizure onset. He denied myoclonic jerks but reported a doubtful history of absences. There was no family history of seizures. He was on carbamazepine with poor seizure control. EEG showed normal background activity with generalized, frontally dominant polyspike and wave discharges at a frequency of 3 Hz. Interestingly, eye closure activated generalized epileptiform discharges, which persisted until eye opening suggesting eye-closed sensitivity ([Fig. 1A]). Photic stimulation revealed a grade IV photo paroxysmal response at 20 Hz ([Fig. 1B]). Magnetic resonance imaging was normal. A diagnosis of idiopathic generalized epilepsy (IGE), likely juvenile absence epilepsy (JAE), was made, and he was switched to sodium valproate, resulting in good seizure control.

Fig. 1 (A) Electroencephalogram (EEG) recorded in an average reference montage demonstrates posterior dominant spike-and-wave discharges (blue arrow) and generalized spike-and-wave discharges (red arrow) persisting throughout eye closure. The epileptiform activity is suppressed upon eye opening and reemerges with eye closure. (Average reference montage: Time base: 30 mm/sec; Sensitivity: 14 uV/mm; High pass filter: 0.3 s; Low pass filter: 70 Hz.) (B) EEG recorded in average reference montage demonstrates a reproducible grade IV photoparoxysmal response elicited by photic stimulation at 20 Hz. (Average reference montage: Time base: 30 mm/sec; Sensitivity: 40 uV/mm; High pass filter: 0.3 s; Low pass filter: 70 Hz).

Epileptiform EEG patterns triggered by eye closure have been categorized into three related phenomena: eye closure sensitivity (ECS), eye-closed sensitivity, and the related term fixation-off sensitivity (FOS). Of these, ECS is more frequent and refers to brief generalized or occipital epileptiform discharges occurring within 2 to 4 seconds of eye closure, typically lasting 1 to 4 seconds, and not persisting throughout the eye-closed state ([Fig. 2]).[1] It has been reported in eyelid myoclonia with absences, idiopathic generalized epilepsies—notably juvenile myoclonic epilepsy, JAE, childhood absence epilepsy, and idiopathic occipital epilepsies.[1] [2] [3] Studies have associated ECS with poorer seizure control and drug-resistant epilepsy in IGE.[3]

Fig. 2 Comparative example of eye-closure sensitivity in a 22-year-old patient with idiopathic generalized epilepsy. Electroencephalogram (EEG) recorded in reference montage reveals transient generalized epileptiform discharges consistently triggered by eye closure, lasting approximately 2 seconds post-eye closure. (Average reference montage: Time base: 30 mm/sec; Sensitivity: 14 uV/mm; High pass filter: 0.3 s; Low pass filter: 70 Hz.)

In contrast, eye-closed sensitivity is a relatively rarer phenomenon, characterized by epileptiform discharges that begin immediately upon eye closure, persist throughout the eye-closed state, and cease with eye opening.[1] [4] Given its link to visual fixation, the term FOS has been used interchangeably.[5] FOS is elicited by eliminating central visual fixation with techniques that include the use of Frenzel goggles, diffusing filters, or eye closure in dim light—allowing ambient light while preventing central fixation. Eye-closed sensitivity/FOS typically manifests as persistent posterior or generalized discharges that begin shortly after eye closure and persist for the duration of fixation loss, disappearing immediately upon eye opening or restoration of fixation.[1] [2] [5] Eye-closed sensitivity/FOS are classically described in childhood occipital epilepsies but have been associated with IGE and occipital lesions too.[1] [2] [5] [6] Patients with eye-closed sensitivity have demonstrated a greater persistence of these abnormalities with advancing age compared to those with ECS.[1] Associated photosensitivity maybe less frequent in eye-closed sensitivity/FOS compared to ECS.[1] [6] In rare instances, both ECS and eye-closed sensitivity/FOS have been reported in patients with IGE.[2] The prognostic implications of eye-closed sensitivity/FOS remain unclear and warrant further investigation.

Photosensitivity, ECS, and eye-closed sensitivity/FOS represent distinct reflex epileptic phenomena mediated by occipital hyperexcitability, though they may overlap in clinical and EEG presentations. A clearer understanding of their appearance and elicitation techniques can aid accurate EEG interpretation and epilepsy diagnosis.

Publication History

Article published online:
24 September 2025

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