Elodie Múrias Lopes

Abstract

Abstract

Abstract
The Deep Brain Stimulation of the Anterior Nucleus of the Thalamus (ANT-DBS) is an effective treatment for refractory epilepsy. In order to assess the involvement of the ANT during voluntary hand repetitive movements similar to some seizure-induced ones, we simultaneously collected videoelectroencephalogram ( vEEG) and ANT-Local Field Potential (LFPs) signals from two epilepsy patients implanted with the PerceptTM PC neurostimulator, who stayed at an Epilepsy Monitoring Unit (EMU) for a 5 day period. For this purpose, a repetitive voluntary movement execution protocol was designed and an event-related desynchronisation/synchronisation (ERD/ERS) analysis was performed. We found a power increase in alpha and theta frequency bands during movement execution for both patients. The same pattern was not found when patients were at rest. Furthermore, a similar increase of relative power was found in LFPs from other neighboring basal ganglia. This suggests that the ERS pattern may be associated to upper limb automatisms, indicating that the ANT and other basal ganglia may be involved in the execution of these repetitive movements. These findings may open a new window for the study of seizure-induced movements (semiology) as biomarkers of the beginning of seizures, which can be helpful for the future of adaptive DBS techniques for better control of epileptic seizures of these patients.

Abstract
Deep brain stimulation of the Anterior Nucleus of the Thalamus (ANT-DBS) is an effective therapy in epilepsy. Poorer surgical outcomes are related to deviations of the lead from the ANT-target. The target identification relies on the visualization of anatomical structures by medical imaging, which presents some disadvantages. This study aims to research whether ANT-LFPs recorded with the Percept (TM) PC neurostimulator can be an asset in the identification of the DBS-target. For this purpose, 17 features were extracted from LFPs recorded from a single patient, who stayed at an Epilepsy Monitoring Unit for a 5-day period. Features were then integrated into two machine learning (ML)-based methodologies, according to different LFP bipolar montages: Pass1 (nonadjacent channels) and Pass2 (adjacent channels). We obtained an accuracy of 76.6% for the Pass1-classifier and 83.33% for the Pass2-classifier in distinguishing locations completely inserted in the target and completely outside. Then, both classifiers were used to predict the target percentage of all combinations, and we found that contacts 3 (left hemisphere) and 2 and 3 (right hemisphere) presented higher signatures of the ANT-target, which agreed with the medical images. This result opens a new window of opportunity for the use of LFPs in the guidance of DBS target identification.

Abstract
The Anterior Nucleus of Thalamus (ANT) Deep Brain Stimulation (DBS) has long been touted as the most effective DBS-target for interrupting seizures in focal refractory epilepsy patients. The ANT is primarily involved in cognitive tasks but has extensive reciprocal connections with motor-related regions, suggesting that it is also involved in motor-cognitive tasks. In this work, we aimed to assess the involvement of the ANT during voluntary upper limbs movements. For this purpose, we analyzed Local Field Potentials (LFPs) signals recorded during a movement protocol from one of the first epilepsy patients implanted with a Percept™ PC system, who performed a 5-day period of simultaneous video electroencephalography (vEEG) and Percept PC-LFPs recordings. We estimated time-frequency maps and performed event-related desynchronization (ERD) or synchronization (ERS) analysis and we found that synchronizations found in left hemisphere 7-17 Hz map corresponded to maximum hand rotations. Positive peaks on the ERD/ERS curve occurred at a similar frequency of the hand movements (1.09-0.99Hz against 1.27-0.90{Hz}. These results suggested that the ANT may be involved in the execution of automatisms. Moreover, we found that ERD/ERS appeared approximately 2 seconds before the movement onset, as it was found on the EEG of healthy subjects performing the same protocol.