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Medial temporal lobe atrophy in patients with refractory temporal lobe epilepsy
L Bonilha1, E Kobayashi, C Rorden
1Neuroimaging Laboratory, Department of Neurology, State University of Campinas, Brazil.
Objective:
The objective of this study was to assess the volumes of medial temporal lobe structures using high resolution magnetic resonance images from patients with chronic refractory medial temporal lobe epilepsy (MTLE).
Methods:
We studied 30 healthy subjects, and 25 patients with drug refractory MTLE and unilateral hippocampal atrophy (HA). We used T1 magnetic resonance images with 1 mm isotropic voxels, and applied a field non-homogeneity correction and a linear stereotaxic transformation into a standard space. The structures of interest are the entorhinal cortex, perirhinal cortex, parahippocampal cortex, temporopolar cortex, hippocampus, and amygdala. Structures were identified by visual examination of the coronal, sagittal, and axial planes. The threshold of statistical significance was set to p<0.05.
Results:
Patients with right and left MTLE showed a reduction in volume of the entorhinal (p<0.001) and perirhinal (p<0.01) cortices ipsilateral to the HA, compared with normal controls. Patients with right MTLE exhibited a significant asymmetry of all studied structures; the right hemisphere structures had smaller volume than their left side counterparts. We did not observe linear correlations between the volumes of different structures of the medial temporal lobe in patients with MTLE.
Conclusion:
Patients with refractory MTLE have damage in the temporal lobe that extends beyond the hippocampus, and affects the regions with close anatomical and functional connections to the hippocampus.
Insights
Patients with refractory medial temporal lobe epilepsy (MTLE) experience volume reductions in brain regions beyond the hippocampus, including the entorhinal and perirhinal cortices. This indicates broader temporal lobe damage in MTLE.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Neuroanatomy
Background:
- Medial temporal lobe epilepsy (MTLE) is a common cause of chronic, refractory epilepsy.
- Assessing structural changes in MTLE is crucial for understanding disease progression and treatment.
- High-resolution MRI aids in detailed volumetric analysis of brain structures.
Purpose of the Study:
- To quantify the volumes of medial temporal lobe structures in patients with chronic refractory MTLE.
- To compare these volumes with those of healthy controls using high-resolution MRI.
- To investigate the extent of structural damage in MTLE beyond the hippocampus.
Main Methods:
- 30 healthy subjects and 25 patients with drug-refractory MTLE were scanned using T1-weighted MRI (1 mm isotropic voxels).
- Correction for field non-homogeneity and linear stereotactic transformation were applied.
- Volumes of the entorhinal cortex, perirhinal cortex, parahippocampal cortex, temporopolar cortex, hippocampus, and amygdala were assessed.
Main Results:
- Patients with MTLE showed significant ipsilateral volume reduction in the entorhinal and perirhinal cortices compared to controls.
- Right MTLE patients exhibited significant asymmetry, with smaller right-sided structures than left-sided.
- No linear correlations were found between the volumes of different medial temporal lobe structures in MTLE patients.
Conclusions:
- Refractory MTLE involves structural damage extending beyond the hippocampus.
- Regions with close anatomical and functional connections to the hippocampus are affected in MTLE.
- These findings highlight the widespread neuroanatomical impact of MTLE.