034-22 – Structural Brainstem Change as a Biomarker for Deep Brain Stimulation Motor Outcomes in Cervical Dystonia

Deep Brain Stimulation (DBS) is a neurosurgical procedure that is performed to ameliorate motor symptoms in movement disorders. DBS is administered in the context of clinical care as a therapeutic option for patients with Cervical Dystonia (CD). CD is a condition that causes involuntary contractions of neck muscles, resulting in abnormal posturing of the neck and head. Although DBS is generally effective at treating the motor symptoms of CD, some patients experience sub-optimal symptomatic alleviation. The pathophysiology of CD is not well understood and as such, biomarkers for DBS motor outcome prediction are lacking. Given that the brainstem is functionally and structurally involved in key motor pathways, the structural profile may posit as a potential determinant for motor outcome response. Here, we assessed the structural profile of the brainstem using pre-operative T1-weighted magnetic resonance imaging (MRI) in 27 patients with CD. Patients who experienced sub-optimal outcomes (n = 14), defined as ≤ 66% Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) reduction pre-and-post DBS, showed structural brainstem differences (p 66% TWSTRS pre-and-post DBS; n = 13). Furthermore, structural connectivity seeded from areas of the brainstem showing structural change resembled the connectivity of well-established motor pathways. Reduced structural volumes of regions from the connectivity map were identified in sub-optimal responders, including the dentate gyrus of the cerebellum (p < .05). Structural changes of the brainstem and cerebellar nuclei may serve as a powerful biomarker to account for and predict motor outcome response in patients with CD. This work serves to highlight the potential efficacy of imaging acquired in the context of clinical care as a means for candidate selection and pathophysiological insight.