Medically Intractable, Localization‐related Epilepsy with Normal MRI: Presurgical Evaluation and Surgical Outcome in 43 Patients

• Published in: Epilepsia (Copenhagen) Vol. 42; no. 7; pp. 883 - 888
• Main Authors: Siegel, Adrian M., Jobst, Barbara C., Thadani, Vijay M., Rhodes, C. Harker, Lewis, Petra J., Roberts, David W., Williamson, Peter D.
• Format: Journal Article
• Language: English
• Published: Boston, MA, USA Blackwell Science Inc 01.07.2001; Blackwell
• Subjects: Adolescent; Adult; Biological and medical sciences; Cerebral Cortex - pathology; Cerebral Cortex - surgery; Cerebrospinal fluid. Spinal cord. Spinal roots. Spinal nerves; Electrodes, Implanted; Electroencephalography - statistics & numerical data; Epilepsies, Partial - diagnosis; Epilepsies, Partial - pathology; Epilepsies, Partial - surgery; Epilepsy; Epilepsy surgery; Epilepsy, Frontal Lobe - diagnosis; Epilepsy, Frontal Lobe - surgery; Epilepsy, Temporal Lobe - diagnosis; Epilepsy, Temporal Lobe - surgery; Female; Humans; Invasive evaluation; Magnetic resonance imaging; Magnetic Resonance Imaging - statistics & numerical data; Male; Medical sciences; Middle Aged; Neurosurgery; Normal MRI; Preoperative Care; Presurgical evaluation; Retrospective Studies; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon - statistics & numerical data; Treatment Outcome; Human; Intracranial; Nervous system diseases; Prognosis; Epilepsy; Epileptic focus; Surgical resection; Nuclear magnetic resonance imaging; Cerebral disorder; Electrodes; Refractory; Electrodiagnosis; Treatment; Partial; Surgery; Central nervous system disease; Medical imagery; Adult; Preoperative
• ISSN: 0013-9580; 1528-1167
• DOI: 10.1046/j.1528-1157.2001.042007883.x

Purpose: High‐resolution magnetic resonance imaging (MRI) plays a crucial role in the presurgical evaluation of patients with medically refractory partial epilepsy. Although MRI detects a morphologic abnormality as the cause of the epilepsy in the majority of patients, some patients have a normal MRI. This study was undertaken to explore the hypothesis that in patients with normal MRI, invasive monitoring can lead to localization of the seizure‐onset zone and successful epilepsy surgery. Methods: A series of 115 patients with partial epilepsy who had undergone intracranial electrode evaluation (subdural strip, subdural grid, and/or depth electrodes) between February 1992 and February 1999 was analyzed retrospectively. Of these, 43 patients (37%) had a normal MRI. Results: Invasive monitoring detected a focal seizure onset in 25 (58%) patients, multifocal seizure origin in 12 (28%) patients, and in six patients, no focal seizure origin was found. Of the 25 patients with a focal seizure origin, cortical resection was performed in 24, of whom 20 (83%) had a good surgical outcome with respect to seizure control. Six of the 12 patients with multifocal seizure origin underwent other forms of epilepsy surgery (palliative cortical resection in two, anterior callosotomy in two, and vagal nerve stimulator placement in two). Conclusions: Successful epilepsy surgery is possible in patients with normal MRIs, but appropriate presurgical evaluations are necessary. In patients with evidence of multifocal seizure origin during noninvasive evaluation, invasive monitoring should generally be avoided.