- Top of page
- PATIENTS AND METHODS
Summary: Purpose: We evaluated the results of cortical resection of epileptogenic tissue for treatment of intractable porencephaly-related epilepsy.
Methods: We examined clinical features, electrophysiological data, surgical findings, and seizure outcomes after cortical resection in eight patients with intractable epilepsy related to porencephalic cysts.
Results: All eight patients had hemiparesis. Five retained motor function in the hemiparetic extremities; six retained visual fields. All had partial seizures, six with secondary generalization. Seven patients had simple and three had complex partial seizures (CPSs); two also had drop attacks. Four patients had multiple seizure types. Long-term scalp video-EEG (LVEEG) localized interictal epileptic abnormalities that anatomically corresponded to the cyst location in three patients. LVEEG recorded ictal-onset zones in five; these anatomically corresponded to the cyst location in three of the five. EEG recorded generalized seizures in two patients, hemispheric in one, and multifocal in two. Intraoperative electrocorticography (ECoG) revealed interictal epileptic areas extending beyond the margins of the cyst in seven patients. We resected ECoG-localized interictal epileptic areas completely in five patients and partially in two. Cortical resection was based on seizure semiology and LVEEG in one patient whose ECoG showed no epileptiform discharges. After a minimum follow-up of 1 year, six patients had excellent seizure outcome (Engel class I), and two had a >90% seizure reduction (Engel class III) without complications.
Conclusions: Cortical resection guided by ECoG allows preservation of motor function and visual field and provides an effective surgical procedure for treatment of intractable epilepsy secondary to porencephaly.
Porencephalic cysts are cavities in the brain resulting from prenatal or perinatal vascular occlusion. Commonly congenital hemiparesis, intellectual impairment, and medically intractable epilepsy are present (1–6). Physicians often discourage surgical intervention because accurate localization of seizure foci in patients with intractable porencephaly-related epilepsy is difficult (7). When surgery is recommended, neurologic status determines the choice of the surgical procedure. Hemispherectomy is the classic treatment option for patients with porencephaly-related epilepsy and maximal or near-maximal congenital hemiparesis and hemianopsia (8–14), whereas partial hemispherectomy or cortical resection with excision of multiple lobes is used in patients who have relatively mild hemiparesis with useful finger movements or preserved visual fields. Lesionectomies, focal epileptogenic corticectomies, or lobectomies have occasionally been performed in patients with focal extratemporal or temporal lobe epilepsy and porencephalic cysts (15–21).
Recently some patients have benefited from temporal lobectomy for coexisting hippocampal sclerosis with extratemporal porencephaly when clinical and EEG findings are concordant with temporal lobe onset of seizures (22,23). However, the majority of patients have still undergone functional hemispherectomy (22).
No systematic studies have focused on focal cortical resection as a surgical option, as an alternative to hemispherectomy, in patients with porencephaly. In this study, we evaluate the benefit of cortical resection for seizure control in eight patients. We examine the clinical histories, electrophysiologic data, epileptogenic area localization corroborated by intraoperative electrocorticography (ECoG), surgical findings, and seizure outcomes.
PATIENTS AND METHODS
- Top of page
- PATIENTS AND METHODS
We studied eight patients who had undergone cortical resections for intractable epilepsy secondary to a porencephalic cyst between 1986 and 2002 at The Montreal Neurological Institute and Hospital. Six were male subjects. We included only patients whose conditions met the clinical diagnosis of porencephalic cyst: a circumscribed brain defect in any cerebral artery territory, revealed on computerized tomographs (CTs) or magnetic resonance images (MRIs) (3–5). Patients may have had a previous history of prenatal or perinatal ischemic brain insults but no other etiologic factors. We excluded patients with cystic lesions that occurred later in life (e.g., after trauma, tumor resection, circulatory disturbances, or infection) and cystic developmental malformations (e.g., schizencephaly or arachnoid cyst) that were visible on CT (24) or MRI (3,25,26). We classified seizures according to the International League Against Epilepsy guidelines (27,28).
We reviewed the medical records of all patients with respect to their past histories; neurologic findings, especially motor disabilities; seizure descriptions and frequencies; neuropsychological assessments; neuroimaging studies; scalp and intracranial EEG findings; and surgical findings. Motor disabilities were evaluated with specific attention to functional aspects. When patients had no voluntary finger movement or foot tapping, we considered them to have maximal hemiparesis. Usually in such patients, their hands barely moved or were spastic, their fists clenched, elbows were fixed, and they limped. When patients had voluntary finger movements, we considered them to have mild hemiparesis. All patients were referred to an ophthalmologist for visual field examination by Goldman perimetry.
All patients had long-term scalp video-EEG (LVEEG) monitoring with electrodes placed according to the International 10-20 system. Sphenoidal electrodes were used when we suspected seizure onset from the mesial temporal region. Preexcision ECoGs with 16 carbon-ball electrodes were recorded to cover the all the borders of the cysts, under general or local anesthesia, supplemented by neuroleptanalgesia with droperidol and fentanyl. One patient underwent intracranial EEG monitoring with depth and epidural electrodes before cortical resection. Only patient 2 was studied with positron emission tomography (PET) for motor-function mapping before the second operation.
We based the area of cortical resection on intraoperative ECoG, LVEEG data, seizure semiology, and anatomic location of the cystic lesion.
We evaluated seizure outcome by using Engel's classification (29) and postoperative complications after a minimum 1-year follow-up.