Voxel-based morphometry of sporadic epileptic patients with mesiotemporal sclerosis

Area of Science:

• Neuroimaging
• Epilepsy Research
• Neuroanatomy

Background:

• Gray matter (GM) abnormalities in refractory temporal lobe epilepsy (rTLE) extend beyond the hippocampus.
• Previous studies noted extrahippocampal GM reductions in mild TLE (mTLE), even without mesiotemporal sclerosis (MTS).
• No studies have directly compared whole-brain GM volume between rTLE and mTLE.

Purpose of the Study:

• To investigate whole-brain GM volume differences between rTLE and mTLE using optimized voxel-based morphometry (VBM).
• To identify GM abnormalities beyond the hippocampus in both mTLE and rTLE with evidence of MTS.

Main Methods:

• Optimized VBM analysis of brain MRI scans from 19 mTLE patients, 19 rTLE patients, and 37 healthy controls.
• Mesiotemporal sclerosis (MTS) diagnosis based on hippocampal atrophy and/or mesiotemporal hyperintensity on FLAIR or T2 images.
• Exclusion of patients with recent generalized tonic-clonic or complex partial seizures.

Main Results:

• Both mTLE and rTLE groups exhibited GM volume reductions in the bilateral thalamus, left hippocampus, and sensorimotor cortex compared to controls.
• No significant differences in GM volume were found between the rTLE and mTLE patient groups.
• Seizure characteristics were controlled for by ensuring no recent generalized tonic-clonic or complex partial seizures.

Conclusions:

• Voxel-based morphometry (VBM) reveals GM reductions beyond the hippocampus in both mTLE and rTLE, primarily affecting the bilateral thalamus.
• The lack of significant GM differences between mTLE and rTLE supports a biologic continuum hypothesis for TLE.
• These findings suggest a potential pathophysiologic role of the thalamus in partial epilepsy.