Thalamic Activity as a Marker of Seizure Onset Laterality

Temporal lobe
Temporal lobe
Thalamic activity has value as a predictive marker of seizure onset laterality.

BALTIMORE — Thalamic functional connections can be specific markers of seizure onset laterality in patients with temporal lobe epilepsy, according to a study findings presented at the 2014 American Neurological Association Annual Meeting.

Daniel S. Barron, MD, of the Yale University School of Medicine, and colleagues assessed whether thalamic resting-state functional connectivity with temporal lobe areas could predict seizure onset laterality in patients with temporal lobe epilepsy (TLE).

A previous meta-analysis of medial TLE patients showed that the thalamus was the most common site of extra-hippocampal gray matter loss, and a subsequent diffusion MRI study conducted by the team showed decreased thalamo-hippocampal structural connectivity in a group of patiets. This study, which compared 24 unilateral TLE patients to 20 age-matched controls, further investigated the thalamo-hippocampal TLE model using resting state functional connectivity based on BOLD-fMRI.

In the study, intracranial EEG was used to establish seizure onset lateralization and mean resting-state fMRI time-series were extracted for thalamic, hippocampal, amygdalar, and entorhinal cortex volumes. The individual scores were used to predict seizure onset laterality for both discriminant and logistic regressions.

The researchers found that two-dimensional discriminant analysis predicted seizure onset zone with 85% sensitivity and 91% specificity compared with four-dimensional logistic regression, which had 86% sensitivity and 100% specificity. The L thalamo-hippocampal and R thalamo-entorhinal cortex functional connections were the strongest markers in both sets.

The novel finding can advance the development of neuroimaging biomarkers that can help guide the clinical evaluation of patients, especially those with complex cases with no detectable lesions. 


  1. Barron DS et al. Abstract #S202 “Thalamic Functional Connectivity Predicts Seizure Laterality in Individual TLE Patients” Presented at: American Neurological Association 2014 Annual Meeting. Oct 12-14, 2014; Baltimore.