Effect of epilepsy magnetic source imaging on intracranial electrode placement

• Published in: Annals of neurology Vol. 65; no. 6; pp. 716 - 723
• Main Authors: Knowlton, Robert C., Razdan, Shantanu N., Limdi, Nita, Elgavish, Rotem A., Killen, Jeff, Blount, Jeffrey, Burneo, Jorge G., Ver Hoef, Lawrence, Paige, Lebron, Faught, Edward, Kankirawatana, Pongkiat, Bartolucci, Al, Riley, Kristen, Kuzniecky, Ruben
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-06-2009; Wiley-Liss
• Subjects: Adolescent; Adult; Biological and medical sciences; Brain - physiology; Brain - surgery; Brain Mapping - instrumentation; Brain Mapping - methods; Child; Child, Preschool; Cohort Studies; Electrodes, Implanted; Electroencephalography - instrumentation; Electroencephalography - methods; Epilepsy - physiopathology; Epilepsy - surgery; Female; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Humans; Infant; Magnetoencephalography - methods; Male; Medical sciences; Middle Aged; Monitoring, Intraoperative - instrumentation; Monitoring, Intraoperative - methods; Nervous system (semeiology, syndromes); Neurology; Neurosurgical Procedures - instrumentation; Neurosurgical Procedures - methods; Prospective Studies; Young Adult; Electrodes; Intracranial; Nervous system diseases; Epilepsy; Central nervous system disease; Cerebral disorder
• ISSN: 0364-5134; 1531-8249
• DOI: 10.1002/ana.21660

Objective
Intracranial electroencephalography (ICEEG) with chronically implanted electrodes is a costly invasive diagnostic procedure that remains necessary for a large proportion of patients who undergo evaluation for epilepsy surgery. This study was designed to evaluate whether magnetic source imaging (MSI), a noninvasive test based on magnetoencephalography source localization, can supplement ICEEG by affecting electrode placement to improve sampling of the seizure onset zone(s).
Methods
Of 298 consecutive epilepsy surgery candidates (between 2001 and 2006), 160 patients were prospectively enrolled by insufficient localization from seizure monitoring and magnetic resonance imaging results. Before presenting MSI results, decisions were made whether to proceed with ICEEG, and if so, where to place electrodes such that the hypothetical seizure‐onset zone would be sampled. MSI results were then provided with allowance of changes to the original plan.
Results
MSI indicated additional electrode coverage in 18 of 77 (23%) ICEEG cases. In 39% (95% confidence interval, 16.4–61.4), seizure‐onset ICEEG patterns involved the additional electrodes indicated by MSI. Sixty‐two patients underwent surgical resection based on ICEEG recording of seizures. Highly localized MSI was significantly associated with seizure‐free outcome (mean, 3.4 years; minimum, >1 year) for the entire surgical population (n = 62).
Interpretation
MSI spike localization increases the chance that the seizure‐onset zone is sampled when patients undergo ICEEG for presurgical epilepsy evaluations. The clinical impact of this effect, improving diagnostic yield of ICEEG, should be considered in surgery candidates who do not have satisfactory indication of epilepsy localization from seizure semiology, electroencephalogram, and magnetic resonance imaging. Ann Neurol 2009;65:716–723