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Fixation-off sensitivity
Summary
Fixation-off sensitivity (FOS) is an EEG abnormality triggered by eye closure, often seen in childhood epilepsy. While it can cause seizures, its inherent risk for epilepsy is considered low.
Area of Science:
- Neurology
- Epileptology
- Clinical Neurophysiology
Background:
- Fixation-off sensitivity (FOS) is a phenomenon characterized by EEG abnormalities upon cessation of central vision.
- It manifests as posterior or generalized epileptiform discharges consistently occurring after eye closure.
Purpose of the Study:
- To define and differentiate Fixation-off sensitivity (FOS) from related phenomena like scotosensitivity and eye closure sensitivity.
- To describe the clinical and EEG characteristics of FOS and its association with various epilepsy types.
Main Methods:
- Review of clinical and EEG data from patients with and without epilepsy, focusing on responses to eye closure.
- Differential diagnosis of FOS, scotosensitivity, and eye closure sensitivity based on established criteria.
Main Results:
- FOS is observed in idiopathic childhood occipital epilepsies, symptomatic epilepsies, and even in non-epileptic individuals.
- It is distinguished from scotosensitivity (darkness-induced) and eye closure sensitivity (triggered by the act of closing eyes).
- FOS is associated with occipital hyperexcitability but has a presumed low intrinsic epileptogenic potential.
Conclusions:
- Fixation-off sensitivity is a distinct phenomenon related to visual fixation cessation.
- While potentially indicative of underlying hyperexcitability, FOS itself has a low risk of causing epilepsy.
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