Inclusion Criteria:  Definitive diagnosis of typical CD by a board certified neurologist. Written informed consent from parent(s)/guardian(s). Consent to enroll into the study will include a written agreement to comply with all the conditions of the study, including attendance at follow-up visits. For cohort 1: age more than 36 months and up to 60 months. For cohort 2: age between 15 months and 36 months. For cohort 3: age less than 15 months.  Exclusion Criteria:  Any significant chronic medical condition other than CD or its complications, including, but not limited to neurological, cardiac, hepatic, renal, hematological, gastrointestinal, endocrine, pulmonary, or infectious disease which would put the subject at increased risk during surgery or which would interfere with interpretation of safety monitoring, at the discretion of clinical Principal Investigator (PI). History of severe allergic reaction or anaphylaxis. Past participation in gene therapy trials or receipt of any other investigational product within 6 months prior to enrollment. Prior intracranial surgery. Any absolute contraindication to immunosuppression. Any absolute contraindication to MRI. Any vaccination less than 1 month prior to gene therapy. Anticipated life expectancy of less than 12 months for any reason. GMFM-88 total raw score >15%. Clinically significant out-of-range lab values, at the discretion of clinical PI.