Inclusion Criteria: 1. Infants with age of ≤24 months. 2. Historical diagnosis of Gaucher disease confirmed by GCase enzyme activity test, and with GBA1 biallelic mutations. 3. Neurological signs and/or symptoms consistent with diagnosis of GD2. 4. Parent(s)/legal guardian(s) of subject must give their consent for subject to enroll in the study. 5. Parent(s)/legal guardian(s) of the subject must agree to comply with the requirements of the study, including providing disease information and support disease assessment of symptoms. Exclusion Criteria: 1. Diagnosis of a significant CNS disease other than GD2 that may be a cause for the patient's GD symptoms or may confound study objectives. 2. Achieved independent gait. 3. Severe visceral symptoms of GD which, in the opinion of the Investigator, would pose an unacceptable risk to the patient or interfere with the patient's ability to comply with study procedures or interfere with the conduct of the study. 4. Clinically active infection (including HIV, HBV, HCV or syphilis). 5. For those receiving enzyme replacement therapy and/or substrate reduction therapy and/or ambroxol for Gaucher disease, stable treatment ≤2 months before enrollment. 6. Use of strong inhibitors or inducers of cytochrome CYP3A4 or P-glycoprotein (P-gp) medications, herbals, or over-the-counter agents. 7. Any type of prior gene or cell therapy. 8. Immunizations (live vaccines) in the prior 4 weeks. 9. Use of systemic immunosuppressant or corticosteroid therapy other than protocol-specified (topical preparations for dermatological conditions are allowed). 10. Patients with anti-AAV9 neutralizing antibody titer over 1:5. 11. Brain MRI (magnetic resonance imaging) showing clinically significant abnormality considered to prevent intracisternal injection. 12. Contraindication to sedation during surgery or imaging studies (PET). 13. Presence of other significant medical conditions that would create an unacceptable risk to the patient or interfere with the patient's ability to comply with study procedures or interfere with the conduct of the study.