Intractable epilepsy after a functional hemispherectomy: important lessonsfrom an unusual case - Case report

Residual seizures after functional hemispherectomy occur in approximately 2 0% of patients with catastrophic epilepsy. These episodes are traditionally attributed to incomplete disconnection, persistent epileptogenic activity in the ipsilateral insular cortex, or bilateral independent epileptogenic a ctivity. The authors report on the case of an 8-year-old boy with an intrac table seizure disorder who had classic frontal adversive seizures related t o extensive unilateral left hemispheric cortical dysplasia. The initial int ervention consisted of extensive removal of the epileptic frontal and prece ntral dysplastic tissue and multiple subpial transections of the dysplastic motor strip, guided by intraoperative electrocorticography. Subsequently, functional hemispherectomy including insular cortex resection was performed for persistent attacks. After a seizure-free period of 6 months, a new pat tern ensued, consisting of an aura of fear, dystonic posturing of the right arm, and unusual postictal hyperphagia coupled with an interictal dienceph alic-like syndrome. Electroencephalography and ictal/interictal single-phot on emission computerized tomography were used to localize the residual epil eptic discharges to deep ipsilateral structures. Results of magnetic resona nce imaging indicated a complete disconnection except for a strip of residu al frontobasal tissue. Therefore, a volumetric resection of the epileptogen ic frontal basal tissue up to the anterior commissure was completed. The ch ild has remained free of seizures during 21 months of follow-up review. Standard hemispherectomy methods provide extensive disconnection, despite t he presence of residual frontal basal cortex. However, rarely, and especial ly if it is dysplastic, this tissue can represent a focus for refractory se izures. This is an important consideration in determining the source of ong oing seizures posthemispherectomy in patients with extensive cortical dyspl asia. It remains important to assess them fully before considering their di sease refractory to surgical treatment.