Left or right? Lateralizing temporal lobe epilepsy by dynamic amygdala fMRI

- BOLD signal increases were generated in the contralateral amygdala to the side of seizure onset in 75% of patients.
- Bilateral BOLD signal increases were noted in all healthy control participants and in patients with non-epileptic seizures.
- Amygdala activations contralateral to side of seizure onset were comparable in the patients with left TLE than right TLE.
- No reliable pattern of BOLD signal changes were noted in patients with bilateral TLE and extra-temporal lobe epilepsy.
- Signal-to-noise ratio was sufficient to provide significant signals in individual cases studied with a 1.5 T scanner.

ObjectivesIn this case series, the findings of 85 functional MRI studies employing a dynamic fearful face paradigm are reported. Previous findings have shown the paradigm to generate bilateral amygdala activations in healthy subjects and unilateral activations in patients with MTLE, in the contralateral hemisphere to seizure origin. Such findings suggest ipsilateral limbic pathology and offer collateral evidence in lateralizing MTLE.MethodsThe series includes 60 patients with TLE, 12 patients with extra-temporal lobe epilepsy, and 13 healthy controls. Functional MRI studies using a 1.5 T scanner were conducted over a three-year period at a single epilepsy center and individual results were compared with EEG findings.ResultsIn the cohort of unilateral TLE patients, lateralized activations of the amygdala were concordant with EEG findings in 76% of patients (77% lTLE, 74% rTLE). The differences in the mean lateralized indices of the lTLE, rTLE, and healthy control groups were all statistically significant. Lateralized amygdala activations were concordant with EEG findings in only 31% of the 12 patients with extra-temporal lobe epilepsy and bilateral amygdala activations were generated in all but one of the healthy control subjects.SignificanceThis case series further endorses the utility of the dynamic fearful face functional MRI paradigm using the widely available 1.5 T as an adjunctive investigation to lateralize TLE.