Abstracts

Rationale: Occipital Lobe Epilepsy (OLE) is an under recognized epilepsy. Non-lesional (about 40%) have a poorer surgical outcome than lesional cases. The concordance of multiple presurgical studies in identifying the epileptogenic zone can help predict a good surgical outcome in published series of patients. Challenges in the evaluation of patients with OLE include rapid seizure spread, most often to the temporal lobe, the critical importance of the timing of ictal SPECT injections (especially during the simple partial seizure phase when the EEG may be bland), the frequent lack of reported visual aura, the lack of EEG specificity in the majority of cases, and intracranial electrode placement unless an occipital focus is suspected. There is also little known about functional impairment after resection of visual associative cortex, particularly in the language dominant hemisphere.Methods: We report three cases of OLE in children and the results of their evaluative studies along with a focused review of reported cases of OLE in the literature to illustrate the challenges outlined above. Results: See Table I. Case series reported in the literature underscore the challenges involved in OLE, with reports of lower usefulness of ictal SPECT studies (attributed to timing of the injection and the rapid propogation into other brain regions), patients with OLE who have had temporal lobectomies with generally an unfavorable outcome, occipital lobe resections with visual field cuts but no report of other deficits acquired. Additionally, a visual aura cannot distinguish idiopathic from symptomatic cases of OLE, and visual aura has been reported in cases of temporal lobe epilepsy as well.Conclusions: Occipital lobe epilepsy presents significant challenges in the clinical recognition of the seizure semiology, often non-localizing surface EEG , the interpretation of ictal SPECT data due to rapid seizure propogation, and in planning intracranial studies for possible surgical resection, as the occipital source of the seizure may easily be overlooked . In addition, there is inadequate information available regarding the functional deficits acquired through surgery in the occipital (non-striate) cortex. Despite these pitfalls, outcome from surgery appears to be very favorable in well-selected and localized candidates.