Network fingerprint of stimulation induced speech impairment in essential tremor

Abstract

ObjectiveTo 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). MethodsMonopolar 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 than validated in a leave-one-out design. ResultsFibers 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 brainstem. In the thalamic area, they ran laterally to the thalamus and postero-medially to the subthalamic nucleus, in close proximity, mainly antero-laterally, to fibers beneficial for tremor control as published by Al-Fatly et al. (2019). The overlap of the respective clinical stimulation settings 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. InterpretationThis 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 ET patients with thalamic DBS.