Abstracts

Rationale: Surgery for occipital lobe epilepsy remains challenging and can leave the patient with a visual field deficit. Predictors of a seizure free outcome need to be identified.Methods: Retrospective review of surgical outcome in occipital lobe epilepsy in a single center series. Clinical variables and location of seizure origin was correlated with outcome.Results: Of 14 patients with occipital seizure onset confirmed by intracranial EEG, 12 underwent epilepsy surgery with corticectomies of the occipital region. One patient was not operated on due to the risk of a visual field deficit, another had a previous temporal lobectomy and refused further corticectomy after occipital seizure onset was confirmed by a second intracranial study. 5 patients had two intracranial studies. Mean age at surgery was 34.5 years and median follow up after surgery was 5.5 years (1- 13.5 years). 6 patients (50%) were Engel’s class I,1 patient (9%) class III and 5 patients (41%) had no lasting improvement (IV). One patient in class IV was initially seizure free for 22 month then recurred. Patients with seizure origin in the inferior or medial surface of the occipital lobes had more often successful surgery (62%) than patients with onset in the lateral occipital regions (25%). Two patients who’s resection included the hippocampus were seizure free and both patients also demonstrated neuronal cell loss in the hippocampus. The one patient with temporal lobectomy, who later on refused further occipital corticectomy, had significant improvement of his seizures but did not become seizure free after the temporal lobectomy. Six patients had a preexisting visual field deficit. Two patients with complete preexisting hemianopsia on visual fields reported postoperative worsening of their vision, which may reflect worsening of motion detection. Three patients had new, expected visual field deficits after surgery. Two patients reported difficulties writing after left sided resection. Presurgically 50% of patients had visual auras. Of the four patients with elementary visual hallucinations three had lateral occipital seizure onset. The presence of visual auras did not correlate with specific location within the occipital lobes and did not predict outcome. Two patients (one seizure free) were non-lesional, all other patients had lesions. Lesionectomy did not guarantee a seizure free outcome.Conclusions: Occipital epilepsy surgery can render patients seizure free in up to 50% of cases. Inferior and mesial occipital onset was associated with a better outcome in this series. The network connections between the occipital cortex and the temporal lobes especially the hippocampus warrant further investigation.