Longitudinal changes in hippocampal morphology before and after temporal lobe epilepsy surgery

Area of Science:

• Neuroimaging
• Epilepsy Research
• Neuroplasticity

Background:

• Temporal lobe epilepsy (TLE) is linked to neocortical thinning, but hippocampal dynamics remain unclear.
• Understanding hippocampal changes is crucial for TLE progression and treatment insights.

Purpose of the Study:

• To investigate progressive morphological changes in the hippocampus before and after epilepsy surgery in TLE patients.
• To compare hippocampal volume and shape changes between TLE patients and healthy controls.

Main Methods:

• Longitudinal case-control neuroimaging study with TLE patients (pre/post-surgery) and healthy volunteers.
• Linear mixed-effects models used to analyze paired MRI scans for hippocampal volume and surface morphology.
• Replication cohort validated key findings.

Main Results:

• No accelerated atrophy in the ipsilateral hippocampus of TLE patients compared to normal aging.
• Progressive hypertrophy of the contralateral hippocampus observed before surgery, further accelerated post-surgery.
• Contralateral hypertrophy linked to epilepsy lateralization, hippocampal sclerosis, and visual memory deficits; focal to bilateral tonic clonic seizures associated with contralateral atrophy.

Conclusions:

• Refractory TLE is characterized by progressive contralateral hippocampal hypertrophy, potentially representing compensatory plasticity.
• These changes correlate with pre- and post-operative cognitive disturbances, particularly in visual memory.
• Unlike cortical thinning, the ipsilateral hippocampus does not exhibit additional atrophy in chronic TLE.