Abnormal gait is often associated with immobility and falls, which in turn lead to loss of functional independence and death. While gait disorders may arise from many different etiologies, dysfunction of the cerebellum (a part of the brain with the function of coordination of movement) leading to gait disorders results in distinct features. Gait ataxia is a specific type of neurological gait disorder and is defined as the presence of abnormal, uncoordinated movements associated with gait. To date, there are limited treatments for ataxia and/or gait disorders. Deep brain stimulation (DBS) is a neurosurgical tool that has been widely used for over twenty years, mainly to treat Parkinson's disease, dystonia, and essential tremor. In this study, we aim to implant DBS in patients with ataxia and/or gait disorder in the cerebellum area, and electrically stimulate them in a titratable and ultimately reversible manner. This study is divided into 3 phases: pre-operative, operative and post-operative phase. The purpose of this pilot study is to evaluate the safety, feasibility, and to validate the DBS of cerebellar cortical and deep nuclei in patients with treatment refractory ataxia. Twelve(12 ) patients will be enrolled in this study.

Inclusion Criteria:

1. Female or Male patients between age 20-70
2. Diagnosis of primary ataxia (inclusive of congenital and hereditary subtypes without other neurological compromise)
3. Head CT scan and cerebral MRI without any structural contraindications for safe DBS
4. Patient able to give written consent
5. Able to comply with all testing, follow-ups and study appointments and protocols

Exclusion Criteria:

1. Active neurologic disease including but not limited to epilepsy and certain brain tumors
2. Secondary ataxia (such as due to stroke, medication, autoimmune disease, ischemia, tumor, or other lesion)
3. Any contraindication to MRI scanning
4. Likely to relocate or move during the study's one-year duration
5. Presence of cardiac arrhythmias, or other cardiac, respiratory, renal or endocrine conditions that will result in significant risk from a surgical procedure.