A meta-analysis of voxel-based morphometry studies on unilateral refractory temporal lobe epilepsy

Purpose: To identify consistent results of voxel-based morphometry (VBM) studies in unilateral refractory temporal lobe epilepsy (TLE).

Methods: Whole-brain VBM studies comparing refractory TLE patients with healthy controls (HC) were systematically searched in PubMed, ISI Web of Science, Embase, and Medline databases from January 1990 to May 2011. Coordinates were extracted from clusters with significant difference in gray matter volume (GMV) between refractory TLE patients and HC. Meta-analysis was performed using activation likelihood estimation (ALE).

Key findings: A total of 6 studies, comprising 180 refractory left TLE (LTLE) patients, 142 refractory right TLE (RTLE) patients, and 283 HC, were enrolled. The included studies reported GMV reduction at 93 coordinates in refractory LTLE, and 46 coordinates in refractory RTLE, as well as GMV increase at 9 coordinates in refractory LTLE, and 8 coordinates in refractory RTLE. Given the small number of studies and coordinates that reported GMV increase, only a subgroup analysis of GMV reduction between refractory LTLE or RTLE and the HC was performed respectively. There were significant reductions in ipsilateral mesiotemporal structures and the bilateral thalamus in both refractory LTLE and refractory RTLE. Abnormalities of bilateral frontal lobe and right cingulate gyrus were also found in the refractory LTLE patients, whereas right insular atrophy was found in the refractory RTLE group.

Significance: The findings suggested that unilateral refractory TLE patients had widespread GMV reduction and asymmetrical areas beyond the mesial temporal structures.