Characteristics of interictal MEG spike dipoles in temporal lobe epilepsy with unilateral amygdala enlargement.

Objective

To clarify the characteristics of MEG findings in patients with temporal lobe epilepsy with amygdala enlargement (TLE-AE).

Methods

We retrospectively identified patients who showed unilateral amygdala enlargement (AE) on MRI and ≥ 5 interictal spikes localized to the ipsilateral temporal region on MEG. Patients were classified into an AE-only group with isolated AE and an AE-plus group with AE plus additional abnormalities. The equivalent current dipole (ECD) model was used to estimate the cortical sources of MEG interictal spikes. The mean pairwise angle (MPA) of the ECD orientations was calculated while the ECD locations were examined. To stabilize the estimates, K-sampling with 1,000 iterations was performed. Group differences were assessed using the Mann-Whitney U test.

Results

Seventeen patients (nine males, aged 18-67 years) met the criteria. The AE-only group (n = 9) showed a significantly higher MPA than the AE-plus group (n = 8, p = 0.046), indicating greater orientation dispersion in the AE-only group. In both groups, the estimated ECDs were located in the anterior and mesial temporal lobes.

Conclusions

Patients with Isolated TLE-AE exhibited more dispersed orientations of MEG interictal spike dipoles than those with concomitant lesions, whereas the dipole locations consistently involved the anterior and mesial temporal lobes.

Significance

Orientation dispersion of the MEG interictal spike dipoles may reflect differences in the epileptogenic networks of patients with TLE-AE.