Cortical-Subcortical morphometric signature of hot water epilepsy patients

Background: Cortical and subcortical grey matter (GM) morphometric changes have been demonstrated Temporal Lobe Epilepsy (TLE) or Idiopathic Generalized Epilepsies (IGE). Hot Water Epilepsy (HWE) has not hitherto been studied in these perspectives.

Purpose: To investigate the cortical and subcortical grey matter in subjects with HWE in terms of thickness, volume, and surface area using Surface-Based Morphometry (SBM). To assess relationships of SBM-derived metrics with clinical variables.

Materials and methods: Ninety-nine people with HWE and 50 age-matched healthy controls underwent high resolution volumetric MRI brain. These were processed with FreeSurfer to obtain SBM parameters i:e cortical thickness, cortical volume, and Cortical surface area. Volumes of seven subcortical GM structures (hippocampus, globus pallidus, nucleus ambiguous(NA), caudate nucleus, putamen, thalamus, and amygdala) were computed. Intergroup morphometric differences and their correlation with epilepsy-specific clinical variables were calculated.

Results: SBM revealed a global reduction in bihemispheric cortical thickness and left hemispheric cortical volume. Besides, a regional difference in the morphometric measures was noted in temporo-limbic, parietal, pre-cuneus, and the cingulate region. Reduced volume of thalami and left caudate alongside an increased volume of the bilateral amygdala, bilateral nucleus ambiguous (NA), right caudate, and putamen was the other cardinal observation.

Conclusion: HWE subjects show alterations in the morphometry of the cortical ribbon and the subcortical grey matter. The temporal semiology, 'reflex nature' pathophysiology correlates involvement of temporo-limbic structures/somatosensory cortex, while the involvement of structures like pre-cuneus, posterior cingulate, and frontal regions are in agreement with functional networks related loss of awareness. That bilateral amygdala swelling occurs in HWE is a novel observation and may signal that it could be a distinct variant of Mesial TLE.