Authors :
Presenting Author: Aida Risman, MD – Emory University
Olivia Marais, MD – Stanford University
Masaya Togo, MD, PhD – Stanford University
Dian Lyu, PhD – Stanford University
Sofia Pantis, BS – Stanford University
Josef Parvizi, MD, PhD – Stanford University School of Medicine
Rationale:
In prior studies using simultaneous thalamic recordings, we identified early seizure-related activity not only in the anterior nucleus of the thalamus (ANT) but also in other thalamic regions, notably the pulvinar (PLV). Building on this body of evidence - and particularly given the early recruitment of non-ANT thalamic nuclei - we sought to determine whether the mediodorsal (MD) nucleus of the thalamus exhibits a distinct and potentially early role in seizure propagation. Moreover, we aimed to map the connectivity of this thalamic sub-region with the rest of the brain and explore the effects of high frequency ( >50Hz) electrical stimulation of this nucleus on the subjective state of the patients. Methods:
We retrospectively reviewed stereo-EEG and clinical data from 26 patients (total of 150 seizures) with multisite thalamic implantations. All patients presented with focal epilepsy of unclear lateralization or origin. Seizure propagation patterns were assessed for thalamic engagement, nucleus of earliest involvement (with emphasis on MD), and temporal sequencing of activity. Timing data were analyzed at the second level to avoid overstating precision. In addition, we collected connectivity data based on cerebro-cerabral evoked potentials (CCEPs) in 25 patients, and subjective reports of the patients during electrical stimulation of the MD in 17 patients.
Results:
Clinically, there were 12 focal to bilateral tonic clonic seizures, 68 focal impaired awareness seizures, 18 focal aware seizures, 27 focal unclear awareness seizures, and 25 electrographic seizures. A majority of seizures had MD involvement (76.6%). Approximately half of these seizures had early propagation to the MD nucleus (48%), but only in rare seizures (4%) was it the clear thalamic lead. In those rare cases, all seizures were of temporal lobe onset. A majority of seizures (60.5%) with MD involvement had spread to the contralateral hemisphere. CCEP data revealed selective but distributed connectivity with a larger mantle of the brain than prefrontal cortex alone. Electrical stimulation of the MD was often associated with unpleasant subjective changes in the visceral domain. Conclusions:
Our study provide novel multimodal information regarding the human MD nucleus with significant translational impact.
Funding: 1R01NS137650-01A1 to JP