Surgical Outcomes in Patients With Extratemporal Epilepsy and Subtle or Normal Magnetic Resonance Imaging Findings

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Abstract

BACKGROUND:

Surgery is an important therapeutic option in patients with medically refractory epilepsy. The combination of an extratemporal epileptic focus and nonlesional magnetic resonance imaging (MRI) was often believed to portend a poor outcome.

OBJECTIVE:

To investigate the outcome and analyze potential prognostic predictors in patients without lesions on MRI who underwent extratemporal resections.

METHODS:

Clinical, presurgical evaluation, invasive monitoring, and postoperative data of patients with high-resolution MRI that was initially reported as nonlesional were reviewed. Patients were reclassified as MRI-positive if an MRI abnormality related to the epilepsy was revealed at the multidisciplinary presurgical patient management conference, or as MRI-negative if imaging remained normal or revealed incidental findings.

RESULTS:

Sixty patients were identified; 72% were MRI-negative. In the original cohort, the median seizure-free duration was 1.32 years (95% confidence interval [CI], 0.16-2.0); probability of seizure freedom at 2 years was 36% (95% CI, 30%–43%). In the MRI-negative group, the median seizure-free duration was 1.52 years (95% CI, 0.12-5.17); probability of seizure freedom at 2 years was 42% (95% CI, 33%–50%). Complete resection of ictal onset areas and absence of acute postoperative seizures were significantly associated with longer seizure freedom (risk ratio 4.9, P = .004; 95% CI, 1.6-16.7 and 22.1, P < .001; 95% CI, 5.9-94.7, respectively).

CONCLUSION:

Among patients with medically refractory MRI nonlesional extratemporal epilepsy, detailed evaluation and subsequent resection leads to seizure freedom in 42% of patients at 2 years.

ABBREVIATIONS:

APOS, acute postoperative seizure

ABBREVIATIONS:

CI, confidence interval

ABBREVIATIONS:

EEG, electroencephalography

ABBREVIATIONS:

FCD, focal cortical dysplasia

ABBREVIATIONS:

PET, positron emission tomography

ABBREVIATIONS:

PMC, patient management conference

ABBREVIATIONS:

VNS, vagal nerve stimulator

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