Authors :
Presenting Author: Siri Harish, BS – University of Pittsburgh Medical Center
Chandana Belly, MS – University of Pittsburgh Medical School
Tipakorn Tumnark, MD – University of Pittsburgh Medical Center
Thandar Aung, MD,MS – University of Pittsburgh Medical School
Jorge González-Martínez, MD,PhD – University of Pittsburgh Medical School
Rationale:
Stereo-electroencephalography (SEEG) has become an essential pre-surgical evaluation for evaluating intractable epilepsy. SEEG exploration of the thalamus has advanced our understanding of epilepsy pathophysiology and increasingly informs surgical decision-making. However, clinical neurophysiological signals of various sub-thalamic activities remain largely unexplored. In this study, we characterized inter-ictal thalamic background activity in patients with drug-resistant epilepsy who underwent SEEG as part of their pre-surgical evaluation. We exclusively included patients with bilateral thalamic depth electrode implantation, enabling within-subject comparisons across hemispheres and nuclei. Electrode placement targeted specific thalamic nuclei, including the anterior thalamic nuclei (Ant), pulvinar (Pul), and medial and lateral geniculate bodies (MGB, LGB) based on clinical hypotheses regarding epileptogenic networks.
Methods:
We reviewed 112 consecutive SEEG cases from Dec 2020 to May 2025, and identified 3 patients with bilateral multi-thalamic sites exploration. We analyzed 2-minutes segments of SEEG recordings from bilateral thalamic contact pairs in wakefulness and sleep. Localization of electrode placement within each nucleus was determined utilizing the automated anatomical labeling version 3 (AAL3) atlas. After determining which contacts held the highest probability of residing in each nucleus, Time-frequency (wave-length transformation) plots were utilized to show the signal change frequency over time for each nucleus during wakefulness and sleep.
Results:
We analyzed a total of 24 thalamic SEEG electrodes implanted bilaterally across three patients with multifocal epilepsy and multi-nuclear thalamic coverage (Patient 1: 6 electrodes; Patient 2: 10; Patient 3: 8). All patients exhibited bilateral epileptogenic zones and were subsequently treated with responsive neurostimulation (RNS). Electrophysiological recordings from 2–4-minute inter-ictal epochs during both wakefulness and sleep revealed nucleus-specific activity patterns. During wakefulness, the ventral anterior (VA) nucleus consistently demonstrated rhythmic beta-band activity (15–30 Hz), while the pulvinar displayed irregular, higher-frequency bursts (≥ 10 Hz). In contrast, sleep recordings revealed that VA activity remained within the beta range, whereas the pulvinar exhibited dynamic fluctuations in both low-frequency (< 10 Hz) and high-frequency (~30 Hz) bands. In two patients, recordings from the lateral and medial geniculate nuclei were also obtained, revealing low frequency (~ 8-10) Hz noted in the LGB which intensified during sleep, whereas the MGB showed dynamic fluctuations in both low frequency (0-5) Hz and high frequency (~ 20Hz) which were more prominent during sleep.
Conclusions:
Distinct electrophysiological profiles were observed between different thalamic nuclei within the same patient at the same time point, underscoring the spatial heterogeneity of thalamic network dynamics. These intra-individual, region-specific patterns may offer critical insight into target selection and neuromodulation strategies for thalamocortical-based therapies.
Funding:
Funding of the Research: None