Inclusion Criteria:
1. Ability to provide signed and dated informed consent.
2. Willingness and ability to comply with all study procedures and protocol requirements for the duration of the study.
3. Age 18 to 64 years.
4. Chronic, non-penetrating, motor incomplete spinal cord injury \[Association Impairment Scale (AIS) grade C or D\] occurring ≥12 months prior to enrollment, resulting in impairment in lower limb function.
5. Ambulatory with residual gait impairment attributable to spinal cord injury.
6. Self-selected gait speed of \< 0.8 m/s as measured by the 10 meter walk test.
7. Score of 2 or less on at least 4 measures on the Ambulation subsection of the SCI-Functional Independence scale (SCI-FIS).
8. In otherwise good general health as determined by medical history and physical examination.
9. Meets all clinical criteria for VNS implantation as determined by the Site PI and clinical care team.
Exclusion Criteria:
1. Any history of spinal cord injuries by penetrating traumatic, non-traumatic or congenital causes.
2. Evidence of right-sided recurrent laryngeal nerve injury on pre-operative laryngoscopy, if required (Note: Participants with a history of right-sided anterior cervical surgery must undergo laryngoscopy prior to surgical scheduling. A finding of right-sided recurrent laryngeal nerve injury results in exclusion).
3. Excessive scar tissue on intraoperative assessment that precludes safe implantation (Note: Participants with a history of left-sided anterior cervical surgery will undergo intraoperative assessment of scar tissue. If excessive scar tissue is deemed to preclude safe implantation, the procedure will be abandoned and the participant excluded for safety reasons. A history of left-sided anterior cervical surgery or prior recurrent laryngeal nerve injury alone does not result in exclusion).
4. Concomitant clinically significant brain injuries.
5. Deficits in language or attention that interfere with study participation.
6. Presence of any other implanted electrical stimulation device.
7. Prior injury to the vagus nerve.
8. Presence of any other implanted investigational device.
9. Neck circumference of \> 18.5 inches or significant overlying tissue and/or scarring that may hinder device communication.
10. Psychiatric, psychosocial, and/or cognitive disorder or impairment that could interfere with study participation as assessed by medical evaluation.
11. Current or past: (a) medical (psychiatric, non-psychiatric) condition, disease, disorder, injury, or disability\*; or (b) non-medical situation or circumstance that, in the opinion of the Site PI, study participation:
1. may pose a significant or undue risk to the person;
2. make it unlikely the person will complete all the study requirements per protocol; or
3. may adversely impact the integrity of the data or the validity of the study results.
\[\*Examples include, but are not limited to, the following types of conditions, diseases or disorders: renal insufficiency or failure, vascular disease, unstable or concerning cardiac disease, endocrinologic concerns (e.g., poorly controlled diabetes), immunosuppression, respiratory issues, psychiatric (e.g., schizophrenia), neurologic (e.g., cognitive, seizure), sickle cell disease, lupus, clotting disorders, active neoplastic disease (excluding basal or squamous cell carcinoma of the skin with intent for curative excision), recent documented history (within the last 3 months) of dysphagia or aspiration difficulty\]
12. Is female and lactating, pregnant, or plans to become pregnant during the study. Participants of child-bearing potential that are sexually active must use a reliable form of birth control. Acceptable birth control methods: (a) sterilization surgery for women, (b) surgical sterilization implant for women, (c) sterilization surgery for men (including all male partners), (d) Long-acting reversible contraceptives (LARC)-implantable rod and Intrauterine Device (IUD), (e) contraceptive shots/injection every 3 months, (f) oral contraceptives (pills), (g) contraceptive patch, (h) vaginal contraceptive ring, and (i) complete abstinence.
13. Abusive use of alcohol or drugs that could interfere with participation, as determined by the Site PI.
14. Concurrently participating in another interventional clinical study.
15. Requires or plans the use of diathermy, transcranial magnetic stimulation, or electroconvulsive therapy (ECT) during the course of the study.
16. Is known to be under incarceration or legal detention as determined by the Site PI.
17. Non-English speaking, unless the enrolling site has an IRB-approved translated consent and qualified medical interpreter resources available in the participant's language to support all study visits and procedures.
