Volume change in amygdala enlargement as a prognostic factor in patients with temporal lobe epilepsy: A longitudinal study.

OBJECTIVE: Considering the clinical heterogeneity of temporal lobe epilepsy with amygdala enlargement (TLE-AE), identifying distinct prognostic subgroups of TLE-AE has clinical implications. Until now, baseline volume of the enlarged amygdala (EAV) has consistently failed to predict prognosis in TLE-AE. Based on studies suggesting that patients responsive to antiepileptic drugs (AEDs) exhibit remission of AE on follow-up imaging, we investigated whether reduction rate of EAV is predictive of long-term prognosis in TLE-AE. METHODS: Sixty-one consecutive patients with two separate magnetic resonance imaging (MRI) scans were enrolled. To utilize longitudinally measured biomarkers in prediction, the period beyond the first MRI acquisition was split into two periods: the "observation window" (period between the two MRIs) and "prediction window" (follow-up period beyond the second MRI). Patients were classified according to their AED responsiveness during the observation window, and AED-responsive patients were further subdivided by initial seizure frequency: (a) AED-responsive patients presenting with low-frequency seizures (<5 seizures/3 mo; Group A, n = 25), (b) high-frequency seizures (≥5 seizures/3 mo; Group B, n = 23), and (c) patients with poor initial treatment response (Group C, n = 13). Multivariate logistic regression models were constructed for identification of prognostic factors. Along with factors obtained at baseline, factors derived from the observation window (annual percentage change of EAV [APCEAV] and initial AED responsiveness) were also considered as potential predictors. RESULTS: Favorable initial treatment response and faster volume reduction rate (APCEAV ≤ -5.0%/y) were identified as factors predictive of achieving overall seizure freedom. Among the AED-responsive patients, Group A (low-frequency seizures) showed slower remission of AE and higher rate of seizure recurrence, whereas Group B (high-frequency seizures) exhibited faster remission of AE and lower rate of seizure recurrence. SIGNIFICANCE: Faster recuperation of AE in patients with initial high-frequency seizures may be indicative of seizure-induced changes. As volume reduction rate serves as a prognostic marker in TLE-AE, short-term MRI follow-up may be useful in prognostication.