V44. Spatially distinct cortico-thalamic networks identified by parallel iEEG and MEG recordings in patients with tremor

Abstract

Question The ventral intermediate nucleus region (VIMr) of the ventrolateral thalamus and the caudal Zona Incerta (cZi) are established targets for deep brain stimulation (DBS) therapy of medication refractory tremor. While the mechanism of action of DBS remains elusive, evidence points to a modulation of a coordinated network of oscillations. Distinct oscillatory activity patterns may allow large scale interactions between different neural structures. Aberrant activity patterns in these oscillatory networks can lead to the manifestation of specific symptoms, such as tremor, that can be treated with DBS. To characterize the oscillatory cortico-thalamic network we performed simultaneous magnetoencephalographic (MEG) and local field potential (LFP) recordings from the VIMr and cZi DBS electrodes in 10 patients (age: 59 ± 2.7 years) with tremor (6 Parkinson’s disease, 3 essential tremor, 1 orthostatic tremor). Methods Simultaneous MEG-LFP recordings were conducted with the patients at rest with eyes open. LFPs were recorded bipolarly from adjacent contact pairs of the DBS electrodes. The lowermost contact pair was targeted at the cZi (01), while the two upper (12, 23) contact pairs targeted at the VIMr. Dynamic imaging of coherent sources (DICS) beamforming was utilized to visualize peaks of frequency specific cortico-thalamic coherence in Montreal Neurological Institute (MNI) space. Significant clusters were identified using Statistical Parametric Mapping (SPM, FWE corrected threshold p Results Two spatially distinct beta band (13–30 Hz) clusters of cortico-subcortical oscillatory network activity were found for the cZi and VIMr contact pairs, respectively. Coupling of oscillatory beta band activity from the cZi was focally localized in the central cerebellum. In contrast, cortico-thalamic beta band coupling was localized in the motor cortex. No significant clusters were found for the alpha band (7–13 Hz). Conclusions Our results suggest a motor network characterized by beta band coherence between the VIMr and motor cortex and between the cZi and the Cerebellum. These findings extend previous reports on cortico-thalamic LFP-EEG coherence from patients with tremor to a cerebellar connection with the cZi. The reported results are in line with findings from cortico-muscular coherence, FDG-PET and resting state fMRI studies that propose the motor cortex, cerebellum and VIMr as key structures in the tremor network.