Surgical Treatment of the Occipital Lobe Epilepsy

Choi, Ha Young; Choi, Cheol; Kim, Hyoung ihl

Abstract

PURPOSE: Although occipital lobe epilepsy may be operable, localization of the epileptogenic zone can be difficult and there is a high risk of postoperative visual loss.
METHODS
Thirteen patients with intractable occipital lobe epilepsy underwent resective surgery. Preoperatively, all underwent video-EEG monitoring using extracranial electrodes and MRI; Nine had PET scans; In ten, who were cortically stimulated with subdural grid electrodes, invasive recordings were made. Foramen ovale electrodes had been previously used in two, and bitemporal depth electrodes in one; Nitemporal and occipital electrodes had been used in one, and a unilateral temporal depth electrode in one. Nine underwent partial occipital resection, which had spared the nonepileptogenic primary visual cortex, and two underwent a total unilateral occipital lobectomy: A temporal lobectomy was performed in two.
RESULTS
Twelve patients experienced visual aura prior to complex partial seizure, and five had quadrantanopsia. In no patient was noninvasive monitoring reliable in localizing the epileptogenic zone, and in eleven patients, this was localized by invasive recordings. Electrocortical stimulation with subdural grid electrodes evoked simple and complex visual phenomena in nine patients, reproduced the same auras in four, induced a typical seizure in two, and provided language mapping in five. Histopathologic findings revealed cortical dysplasia in five; Tuberous sclerosis was combined in one, hamartoma and ganglioglioma, each in two, and infarction and nonspecific change in the occipital lobe each in one, neuronal loss in the hippocampus and neuronal heterotopia in mesial temporal structures were reported in two patients who underwent temporal lobectomy. Ten were seizure-free during follow-up between six and 46(mean 22.3) months. Seizures recurred in two and were unchanged in one. Only two patients with preoperative quadrantanopsia developed homonymous hemianopsia.
CONCLUSION
This study suggests that in the surgical treatment of the occipital lobe epilepsy, the use of intracranial EEG and functional mapping with subdural grid electrodes, can achieve a good outcome, including the preservation of vision.