Network Fingerprint of Stimulation‐Induced Speech Impairment in Essential Tremor

Abstract

Objective This study was undertaken to gain insights into structural networks associated with stimulation‐induced dysarthria (SID) and to predict stimulation‐induced worsening of intelligibility in essential tremor patients with bilateral thalamic deep brain stimulation (DBS). Methods Monopolar reviews were conducted in 14 essential tremor patients. Testing included determination of SID thresholds, intelligibility ratings, and a fast syllable repetition task. Volumes of tissue activated (VTAs) were calculated to identify discriminative fibers for stimulation‐induced worsening of intelligibility in a structural connectome. The resulting fiber‐based atlas structure was then validated in a leave‐one‐out design. Results Fibers determined as discriminative for stimulation‐induced worsening of intelligibility were mainly connected to the ipsilateral precentral gyrus as well as to both cerebellar hemispheres and the ipsilateral brain stem. In the thalamic area, they ran laterally to the thalamus and posteromedially to the subthalamic nucleus, in close proximity, mainly anterolaterally, to fibers beneficial for tremor control as published by Al‐Fatly et al in 2019. The overlap of the respective clinical stimulation setting's VTAs with these fibers explained 62.4% (p < 0.001) of the variance of stimulation‐induced change in intelligibility in a leave‐one‐out analysis. Interpretation This study demonstrates that SID in essential tremor patients is associated with both motor cortex and cerebellar connectivity. Furthermore, the identified fiber‐based atlas structure might contribute to future postoperative programming strategies to achieve optimal tremor control without speech impairment in essential tremor patients with thalamic DBS. ANN NEUROL 2021;89:315–326

Structural Connectivity of Subthalamic Nucleus Stimulation for Improving Freezing of Gait

“…Considering that stimulation amplitude is also often increased in patients, who are affected more severely or respond poorly to DBS ("non-responder"), this could lead to an over-representation of non-responding patients in the tractography analysis. Such an adjustment is in line with other DBS mapping studies that controlled for the amplitude [33][34][35] .…”

Modeling the volume of tissue activated in deep brain stimulation and its clinical influence: a review

“…Here, several groups have tried using VTA models to solve this task. For example, similar to Tsuboi’s characterization of stimulation induced dyskinesia in PD, Petry-Schmelzer et al sought to determine the brain network fingerprint of stimulation induced dysarthria in ET patients as well as build a predictive model for stimulation related speech intelligibility after thalamic DBS ( Petry-Schmelzer et al, 2021 ). FEM-based VTAs were used to evaluate structural connectivity using a discriminative fiber tract analysis within a normative connectome.…”

Lateral cerebellothalamic tract activation underlies DBS therapy for Essential Tremor

“…This medial activation profile aligns with the face-related cellular somatotopy of internal VIM [ 71 ] as well as a study by Matsumoto and colleagues showing that stimulation-induced dysarthria occurred with more medial thalamic stimulation [ 77 ]. Other studies have also suggested that stimulation overlapping the CTT was a possible cause of dysarthric worsening of intelligibility [ 27 , 28 ]. Our findings are consistent with these past studies and further suggest that the anterior VIMi afferents of the CTT are specifically those responsible for stimulation-induced dysarthria.…”

“…Recent connectomic and tractography studies have focused on the cerebellothalamic tract (CTT) as an effective target for therapy [ 8 , 22 - 26 ]. However, other studies suggest that CTT may also be responsible for stimulation-induced side effects [ 27 , 28 ].…”