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A Comprehensive Protocol for Manual Segmentation of the Medial Temporal Lobe Structures
Published on: July 2, 2014
Morphometric MRI analysis of the parahippocampal region in temporal lobe epilepsy
N Bernasconi1, A Bernasconi, Z Caramanos
1Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada. neda@bic.mni.mcgill.ca
Abstract:
Despite neuropathological and electrophysiological evidence for the involvement of parahippocampal structures in temporal lobe epilepsy (TLE), little attention has been paid to morphometric changes in these structures, and the relation of these changes to TLE. We performed high-resolution MRI volumetric analysis to examine in vivo the morphology of the parahippocampal region in 20 healthy subjects and 6 TLE patients with MRI evidence of unilateral hippocampal atrophy. In normal controls the standardized volume of the left entorhinal cortex (EC) was 1305 +/- 138 mm3 and that of the right EC was 1376 +/- 170 mm3; the left perirhinal cortex (PC) was 2900 +/- 554 mm3 and the right PC was 2771 +/- 486 mm3; the left posterior parahippocampal cortex (PPC) was 2499 +/- 583 mm3 and the right PPC was 2234 +/- 404 mm3. Using a 2 standard deviation cutoff from the mean of normal controls, we found ipsilateral to the seizure focus: (i) a reduction in the volume of the EC in all patients; (ii) a reduction of the PC in 2/6 (33%) patients; (iii) no reduction in the volume of the PPC in any patient. In 3/6 (50%) of patients, the EC was also abnormally small contralateral to the seizure focus. In patients with unilateral TLE, the EC is the most affected structure within the parahippocampal region. Whether this is due to a primary role of the EC in the genesis of TLE or is the consequence of its pivotal position in the reciprocal flow of information between the hippocampus and the neo- and limbic cortices remains to be explored.
Insights
Temporal lobe epilepsy (TLE) patients show reduced entorhinal cortex (EC) volume. This study investigated parahippocampal structure changes in TLE, finding the EC most affected, ipsilateral and sometimes contralateral to the seizure focus.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Brain Morphology
Background:
- Neuropathological and electrophysiological studies implicate parahippocampal structures in temporal lobe epilepsy (TLE).
- Morphometric changes in these TLE-related structures remain under-investigated.
- Understanding these changes is crucial for TLE pathogenesis and treatment.
Purpose of the Study:
- To investigate in vivo the morphology of the parahippocampal region in TLE patients.
- To examine the relationship between morphometric changes and TLE.
- To identify which parahippocampal structures are most affected in unilateral TLE.
Main Methods:
- High-resolution MRI volumetric analysis was performed.
- 20 healthy subjects and 6 TLE patients with unilateral hippocampal atrophy were studied.
- Standardized volumes of entorhinal cortex (EC), perirhinal cortex (PC), and posterior parahippocampal cortex (PPC) were measured.
Main Results:
- All TLE patients exhibited reduced ipsilateral EC volume.
- Reduced PC volume was observed in 33% of patients.
- No PPC volume reduction was found in any patient.
- 50% of patients showed abnormally small contralateral EC volume.
Conclusions:
- The entorhinal cortex (EC) is the most affected structure in the parahippocampal region in patients with unilateral TLE.
- The EC's role in TLE genesis or its position in information flow warrants further investigation.
- These findings highlight the EC's significance in TLE pathophysiology.
