Abnormalities of thalamus and thalamocortical pathways in patients with refractory epilepsy caused by focal cortical dysplasia - MRI study.

OBJECTIVE

Drug-resistant epilepsy, a severe and diagnostically challenging neurological condition often linked to focal cortical dysplasia (FCD), represents a significant social and healthcare burden. While the thalamus is notably altered in this disorder, it remains unclear whether these changes result from epilepsy manifestation or participate in its pathophysiology. This study aimed to characterize volumetric and microstructural changes in the thalamus and thalamocortical pathways in epilepsy patients with FCD.

METHODS

We prospectively enrolled 24 patients with drug-resistant epilepsy caused by FCD and 16 age-matched healthy controls. Diffusion MRI data and quantitative T1 were acquired, and advanced diffusion techniques - Diffusion Kurtosis Imaging (DKI), Neurite Orientation Dispersion and Density Imaging (NODDI), and Fixel-Based Analysis (FBA) - were employed.

RESULTS

Volumetric analysis revealed a significant reduction in thalamic volume ipsilateral to the epileptic lesion. Microstructural analysis identified bilateral alterations in thalamocortical tracts, including changes in both DKI and NODDI diffusion metrics, indicating tissue disorganization and axonal integrity loss. However, no significant microstructural differences were observed between ipsilateral and contralateral thalami, suggesting that thalamic changes may be a consequence of epilepsy rather than its cause.

SIGNIFICANCE

This study investigates widespread structural and microstructural disruptions in the thalamus and thalamocortical networks in drug-resistant epilepsy due to FCD, providing valuable insights into its complex pathophysiology and laying the groundwork for future research utilizing advanced diffusion imaging and analysis techniques.

PLAIN LANGUAGE SUMMARY

This study used advanced MRI techniques to examine the thalamus - a deep brain structure that relays signals and helps coordinate brain activity - in people with focal epilepsy caused by abnormal development of the cerebral cortex, the part of the brain responsible for thinking, movement, and sensory processing, and where seizures often begin. Researchers found subtle structural changes in the thalamus and its connections to the cortex, even beyond the area directly affected by the lesion. These results provide new insight into how epilepsy can disrupt brain networks and offer a foundation for future studies using modern neuroimaging techniques.