Purpose or Case Report: Single stage corpus callosotomy is a surgery utilized in patients with intractable epilepsy that prevents the spread of seizure impulses to the contralateral hemisphere. This study aimed to evaluate post corpus callosotomy findings on fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT), specifically a finding noted in which a cerebral hemisphere demonstrated new (compared to baseline PET-CT) hypometabolism without corresponding magnetic resonance imaging (MRI) lesion. Our aim was to determine if this finding had clinical relevance in predicting post procedure seizure rates.
Methods & Materials: A retrospective chart review was completed including 17 patients at our institution who had corpus callosotomy with both pre and post-surgical PET-CT. The medical records were reviewed for pre and post-operative seizure symptoms, in addition to findings on electroencephalogram (EEG), MRI, PET-CT, and single-photon-emission CT (SPECT). Surgical outcomes were evaluated using an institutionally implemented seizure reduction classification scale. Additionally, criteria from the International League Against Epilepsy (ILAE) classification system for epilepsy surgery outcomes were utilized for assessment.
Results: Of the initial seventeen patients undergoing corpus callosotomy, 6 (35%) demonstrated new diffuse hemispheric hypometabolism on PET-CT without associated MR lesion. Of the 6 patients with hemispheric hypometabolism, 1 was lost to follow-up. All (100%) of the remaining 5 had greater than 90% seizure reduction. Of the 9 patients without hemispheric hypometabolism, 4 (44%) showed greater than 90% seizure reduction. Three out of 5 with hemispheric hypometabolism (60%) were categorized as ILAE class 1 (i.e. completely seizure free). Two out of 9 without cerebral hypometabolism (22%) were categorized as ILAE class 1.
Conclusions: New diffuse hemispheric hypometabolism is frequently seen on PET-CT after corpus callosotomy. In our review, this finding is associated with a higher likelihood of having greater than 90% seizure reduction rate and a higher rate of seizure free status as compared to patients without diffuse cerebral hemispheric hypometabolism. Further studies are needed given the low number of patients in this cohort.