Subthalamic Nucleus Deep Brain Stimulation Modulates Strabismus in Parkinson’s Disease

Objective Parkinson’s disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms. Visual impairments, such as strabismus (misalignment of the eyes during gaze holding), affect up to two-thirds of PD patients, impacting their quality of life. Conventional treatments offer limited relief, prompting exploration of alternatives like deep brain stimulation (DBS) of subthalamic nucleus (STN). This pilot study aims to assess whether STN DBS can alleviate PD-related strabismus and identify specific STN regions associated with favorable outcomes. We hypothesize that STN DBS improves strabismus by modulating subthalamic connectivity with the cerebellum, hence volume of activate tissue (VTA) generated with DBS will be in dorsal STN. Methods We studied 12 PD patients with bilateral STN DBS and five healthy controls. Clinical assessments, eye movement measurements using high-resolution eye tracking, and patient-specific DBS models were employed. Analysis included the VTA models, revealing distinct effects based on the location within the STN. Results We found significant strabismus in 66% of PD patients. STN DBS improved strabismus in 75% of cases. The improvement was associated with dorsal STN stimulation. STN DBS exacerbated strabismus in 25% of PD patients. The VTA in these participants were located in the ventral aspect of the STN. Discussion The findings highlight the significant effects of STN DBS on strabismus in PD, further offering insights into the complex interplay between neurodegeneration and control of eye alignment. This approach, combining clinical assessments, advanced eye tracking, and DBS computational modeling, contributes valuable knowledge towards targeted interventions for visual impairments in PD.