Altered thalamic connectivity patterns in pediatric temporal lobe epilepsy: A gradient mapping study

Area of Science:

• Neuroscience
• Pediatric Neurology
• Epilepsy Research

Background:

• The thalamus plays a crucial role in seizure propagation and is a target for neuromodulation in epilepsy.
• Pediatric temporal lobe epilepsy (TLE) presents unique challenges due to diverse etiologies and impacts on brain maturation.
• Previous studies on thalamic connectivity changes in TLE have primarily focused on adults.

Purpose of the Study:

• To investigate whole-brain thalamic connectivity patterns in children with TLE using a novel gradient mapping technique.
• To compare thalamic connectivity gradients between pediatric TLE patients and healthy controls.
• To examine associations between thalamic connectivity gradients and clinical factors like seizure history, hippocampal sclerosis, and surgical outcomes.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was performed on 62 children with TLE (ages 5-18) and 61 controls (ages 6-20) during a covert verb generation task.
• Thalamic connectivity gradients were computed to identify primary axes of variation.
• Statistical comparisons were made between groups, and correlations with clinical variables were analyzed.

Main Results:

• Two primary thalamic connectivity gradients were identified: an anterior-posterior axis (G1) and a superior-inferior axis (G2).
• Children with TLE exhibited increased thalamic connectivity to the bilateral basal ganglia and mesial temporal regions compared to controls.
• Increased anterior thalamic-basal ganglia connectivity correlated with a history of focal to bilateral tonic-clonic seizures (FBTCS).
• Hippocampal sclerosis was linked to reduced thalamo-hippocampal connectivity, with stronger ipsilateral connectivity predicting better surgical outcomes.

Conclusions:

• Pediatric TLE is characterized by distinct thalamic connectivity patterns, including heightened connections to the basal ganglia and mesial temporal regions.
• Findings suggest a potential inhibitory role of basal ganglia output in modulating thalamo-cortical seizure transmission.
• Thalamo-hippocampal connectivity may serve as a predictive marker for post-surgical seizure control in pediatric TLE.