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Investigating Long-term Synaptic Plasticity in Interlamellar Hippocampus CA1 by Electrophysiological Field Recording
Published on: August 11, 2019
Extrahippocampal gray matter loss and hippocampal deafferentation in patients with temporal lobe epilepsy
Leonardo Bonilha1, Jonathan C Edwards, Stephen L Kinsman
1Division of Neurology, Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA. bonilha@musc.edu
Purpose:
Medial temporal epilepsy (MTLE) is associated with extrahippocampal brain atrophy. The mechanisms underlying brain damage in MTLE are unknown. Seizures may lead to neuronal damage, but another possible explanation is deafferentation from loss of hippocampal connections. This study aimed to investigate the relationship between hippocampal deafferentation and brain atrophy in MTLE.
Methods:
Three different MRI studies were performed involving 23 patients with unilateral MTLE (8 left and 15 right) and 34 healthy controls: (1) voxel-based morphometry (VBM), (2) diffusion tensor imaging (DTI) and (3) probabilistic tractography (PT). VBM was employed to define differences in regional gray matter volume (GMV) between controls and patients. Voxel-wise analyses of DTI evaluated differences in fractional anisotropy (FA), mean diffusivity (MD) and hippocampal PT. Z-scores were computed for regions-of-interest (ROI) GMV and peri-hippocampal FA and MD (to quantify hippocampal fiber integrity). The relationship between hippocampal deafferentation and regional GMV was investigated through the association between ROI Z scores and hippocampal fiber integrity.
Results:
Patients with MTLE exhibited a significant reduction in GMV and FA in perihippocampal and limbic areas. There was a decrease in hippocampal PT in patients with MTLE in limbic areas. A significant relationship between loss of hippocampal connections and regional GMV atrophy was found involving the putamen, pallidum, middle and inferior temporal areas, amygdala and ceberellar hemisphere.
Discussion:
There is a relationship between hippocampal disconnection and regional brain atrophy in MTLE. These results indicate that hippocampal deafferentation plays a contributory role in extrahippocampal brain damage in MTLE.
Insights
Hippocampal deafferentation, or loss of connections, is linked to brain atrophy in medial temporal lobe epilepsy (MTLE). This suggests that disrupted hippocampal pathways contribute to extrahippocampal brain damage in MTLE patients.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Brain Anatomy
Background:
- Medial temporal lobe epilepsy (MTLE) is characterized by extrahippocampal brain atrophy.
- The precise mechanisms driving brain damage in MTLE remain unclear.
- Potential causes include direct neuronal damage from seizures or deafferentation due to lost hippocampal connections.
Purpose of the Study:
- To investigate the relationship between hippocampal deafferentation and extrahippocampal brain atrophy in MTLE.
- To explore whether loss of hippocampal connections contributes to brain damage beyond the hippocampus.
Main Methods:
- Utilized MRI including voxel-based morphometry (VBM), diffusion tensor imaging (DTI), and probabilistic tractography (PT) in 23 MTLE patients and 34 controls.
- Assessed regional gray matter volume (GMV) differences and quantified hippocampal fiber integrity using fractional anisotropy (FA) and mean diffusivity (MD).
- Examined the association between hippocampal deafferentation metrics and regional GMV atrophy.
Main Results:
- MTLE patients showed reduced GMV and FA in perihippocampal and limbic areas.
- Hippocampal probabilistic tractography was decreased in limbic areas for MTLE patients.
- Significant correlations were found between hippocampal connection loss and GMV atrophy in the putamen, pallidum, temporal lobes, amygdala, and cerebellum.
Conclusions:
- A significant relationship exists between hippocampal disconnection and regional brain atrophy in MTLE.
- These findings indicate that hippocampal deafferentation is a contributing factor to extrahippocampal brain damage in MTLE.
