Interposed Nucleus aDBS for Ataxia

Inclusion Criteria: * A diagnosis of SCA6 by a movement disorders specialist following established criteria recommended by the Movement Disorders Society * A positive genetic test for SCA6 * A total score ≥ 8 on the Scale of the Assessment and Rating of Ataxia (SARA) rating scale * Ability to walk with or without support (score \<8 on the 'gait' subsection of the SARA rating scale) * Age ≥ 21 years and \<89 years * Ability to give informed consent for the study * Ability to understand the study protocol Exclusion Criteria: * Inability or unwillingness to comply with the study protocol * History of previously implanted neurostimulators, pacemakers, defibrillators, or metallic head implants * Severe cognitive impairment or dementia, defined as a score \<21 on the Montreal Cognitive Assessment (MOCA) * Evidence of ataxia due to other etiologies, including but not limited to: * Genetic/inherited disorders other than SCA6 * Acquired causes: traumatic brain injury, multiple sclerosis, paraneoplastic cerebellar degeneration, infections or post-infectious cerebellitis, autoimmune ataxias (e.g., anti-GAD, gluten ataxia) * Toxic/metabolic causes: alcoholic cerebellar degeneration, vitamin deficiencies * Structural, vascular, or neoplastic causes: cerebellar stroke, tumors, congenital malformations * Suspected multiple system atrophy-cerebellar type (MSA-C) * Presence of active and untreated psychiatric illness, severe depression (Beck Depression Inventory ≥ 21), or personality disorder at the discretion of the study team * Coagulopathy, uncontrolled epilepsy, or other medical conditions that are considered to place the patient at elevated risk for surgical complications * Presence of a concomitant medical condition that, in the investigator's opinion, may interfere with the study participation or gait/balance, for example, severe arthritis * Requirement of diathermy, electroconvulsive therapy, or transcranial magnetic stimulation * Pregnancy or lactation * Active suicidal ideation, defined as fined as a "Yes" response to questions #2-5 within the past one month on the Columbia Suicide Severity Rating Scale, C-SSRS * Refractory epilepsy