Abstracts

Rationale: FOS phenomenon is characterized by posterior focal or generalized epileptfiform discharges or seizures that are induced by elimination of central vision/fixation typically by eye closure. FOS is observed in patients with idiopathic childhood occipital epilepsies, but may also be seen in symptomatic or cryptogenic focal and generalized epilepsies.[1] Though FOS may persist into adulthood, these cases are thought to represent a "prolongation" of the same phenomenon that arose in childhood. [2] [1] Brigo F, et al. Fixation-off sensitivity. Clin Neurophys. 2013; 124 (2): 221-227. [2] Fattouch J, et al. The spectrum of epileptic syndromes with fixation off sensitivity persisting in adult life. Epilepsia. 2013; 54 Supplement 7: 59-65. Methods: We present a case of FOS-like phenomenon observed in an adult patient who suffered acute embolic strokes in the parietal and occipital regions followed by new onset occipital seizures. Results: A 50 yo gentleman had aortic valve replacement surgery for aortic stenosis. Hours after the procedure, the patient had a generalized tonic-clonic seizure. Despite treatment with IV Levetiracetam and repeated doses of IV Lorazepam, the patient suffered additional secondarily generalized tonic -clonic events that were preceded by limb posturing and versive head turning to the left. He was intubated, started on continuous video-EEG monitoring (CEEG), and placed on a Propofol drip. CEEG recorded both clinical and subclinical seizures characterized by independent, bilateral seizures originating from the posterior regions. Propofol drip was titrated until modified burst suppression was achieved. Cardiac monitoring revealed atrial fibrillation with rapid ventricular rate of 110-140 beats per minute. MRI brain demonstrated multiple foci of diffusion restriction scattered throughout the white matter, most prominent in the parietal and occipital lobes strongly suggestive of acute embolic infarcts. No further seizures were recorded after 2 days of CEEG. The patient was successfully weaned off Propofol and extubated. A portable EEG 1 day later showed mild diffuse background slowing and frequent runs of high amplitude, spike/sharp wave complexes at 3-4 Hz frequency in the occipital regions lasting 10-20 seconds in duration. Other than the response to eye closure, there was no clinical correlate to the occipital activity (Figures 1 & 2). The patient was maintained on Levetiracetam and no further seizures were observed. Conclusions: Typically described in the pediatric population, FOS is thought to be modulated by α-rhythm generators and influenced by cortical hyperexcitability.[3] This is a novel case where FOS-like phenomenon was acutely observed in an adult patient with new onset seizures and posterior cerebral infarcts reflecting a shared mechanism of posterior cortical hyperexcitability. [3] Koutroumanidis M, et al. Fixation-off sensitivity in epilepsies other than the idiopathic epilepsies of childhood with occipital paroxysms: a 12-year clinical video-EEG study. Epileptic Disord. 2009:11:20-36.