Electroclinical Presentations of Fixation-off Sensitivity in Adults With Symptomatic Epilepsy

Fixation-off sensitivity (FOS) is a discharge pattern on EEG that occurs owing to the loss of central vision or fixation. Knowledge regarding the relationship between FOS and symptomatic epilepsy is limited. Therefore, we aimed to evaluate the electroclinical features of FOS in adult patients with symptomatic epilepsy.

Outpatient video-EEG records of the Hacettepe University Faculty of Medicine were reviewed from 2009 to 2019. Patients aged >18 years with symptomatic epilepsy with a FOS pattern were included. Demographic, clinical, EEG, and neuroimaging data were retrospectively evaluated from an electronic database and patient files.

Eight patients (50% female) were included in this study; seven (87%) had refractory epilepsy. Prominent risk factors were family history of epilepsy in five patients and prenatal/natal insult in four patients. Notable MRI signs included cortical developmental malformation, posterior gliosis, and frontoparietal porencephalic cyst. The FOS pattern was generalized with posterior emphasis in two patients and lateralized or localized in six patients: frontocentroparietal ( n = 1) and temporoparietooccipital ( n = 5). Fixation-off sensitivity discharges were found to be increased by hyperventilation and decreased by drowsiness and sleep in 50% of patients. Fixation-off sensitivity disappeared in one patient with good seizure control.

In this study, the disappearance of FOS in an epileptic patient with a structural lesion and detection of FOS activity related to a frontoparietal porencephalic cyst were remarkable. Family history of epilepsy was also substantially high. Our results indicate that the underlying mechanism of FOS is much more complicated than previously thought.