The purpose of this study is to evaluate the safety and possible effectiveness of deep brain stimulation (DBS) of the nucleus accumbens in children with autism spectrum disorder and treatment-refractory, repetitive self-injurious behavior. Six (6) patients will be recruited and enrolled in this pilot study and study duration for each patient will be one (1) year. All will undergo surgical implantation of the Medtronic DBS system and will receive stimulation of the nucleus accumbens (2 electrodes per patient).This will be an open, non-blinded, non-randomized, pilot, phase I trial.Expected study duration is 36 months.

This is a phase I, non-blinded, non-randomized, pilot trial for safety and efficacy of deep brain stimulation for medically-refractory, repetitive self-injurious behaviours in children with ASD (i.e. secondary stereotypies). The trial will be conducted in compliance with the protocol, GCP and the applicable regulatory requirement(s).

Patients who meet inclusion and exclusion criteria will be identified and recruited the Neurosurgical Clinic at The Hospital for Sick Children. The study will proceed according to the schedule laid out below, and both patients and treating team will be aware of all treatment parameters at all times. Six (6) subjects will be enrolled in this study and study duration for each patient will be one (1) year. Previous phase I trials of DBS in psychiatric and Alzheimer's Disease populations have utilized 6 subjects per surgical target. Such a number is sufficient to demonstrate initial safety, as well as feasibility and clinical effectiveness.

Inclusion Criteria:

• Female or Male patients between age 7-18
• Diagnosis of Autism Spectrum Disorder (as defined by the DSM-5).
• Failure or non eligibility of medical therapy with ongoing repetitive self-injurious behaviours, at 6 months or more after instigation of therapy. Failure is defined as a lack of improvement in self-injurious behaviours, as documented by objective evidence, including caregiver logs or clinician assessment, if the clinician has documented a baseline status prior to instigation of the medical therapy.
• Diagnosis of secondary stereotypies, based on clinical assessment of the treating physicians with evidence of self-injury, documented in the patient records.
• Parents or legal guardians, including caregivers, informed and able to give written consent.
• Able to comply with all testing, follow-ups and study appointments and protocols for 12 months following the end of the duration of the study.

Exclusion Criteria:

• Substance dependence or abuse in the last 6 months, excluding caffeine and nicotine
• Any contraindication to MRI or PET scanning
• Likely to relocate away from the study site or move during the study's one year duration
• Presence of cardiac arrhythmias, or other cardiac, respiratory, renal or endocrine conditions that will result in significant risk from a surgical procedure.
• Pregnancy
• Unable to communicate adequately in English in order to complete the baseline and follow-up questionnaires.