Inclusion Criteria:
* 18 years ≤ age ≤ 65 years, male or female;
* Cervical spinal cord injury (injury level C2-C6), with ASIA Impairment Scale grade A, B, or C;
* Severe impairment of hand function on the target upper extremity: finger flexor muscle strength \< grade 3 as assessed by the ISNCSCI scale;
* ARAT score ≥ 2 for "hand to mouth"; score ≥ 1 for both "hand to top of head" and "hand to back of head"; and scores ≤ 1 for each of the grasp, grip, and pinch tasks;
* Neurological assessment confirms normal motor-related cortical function of the brain, with no acute cerebral functional changes;
* At least 12 months have elapsed since the cervical spinal cord injury resulting in tetraplegia, and the condition has been stable for at least 6 months following standardized treatment (with documentation of rehabilitation therapy records available);
* Good cognitive function: Mini-Mental State Examination (MMSE) score ≥ 22 and Montreal Cognitive Assessment (MoCA) score ≥ 26 ;
* Possess the basic visual, auditory, and language comprehension abilities required for interaction, and be able to cooperate with training;
* The subject voluntarily participates and is willing to comply with the relevant examinations and follow-up visits.
Exclusion Criteria:
* Neurodegenerative diseases / secondary injury due to tumors, or severe autonomic dysreflexia;
* Presence of intracranial lesions or contraindications to intracranial implantation: active epilepsy or definite epileptogenic tendency; severe cerebrovascular disease; brain tumor; moderate-to-severe sequelae of traumatic brain injury; space-occupying lesions or structural abnormalities at the electrode implantation target area; already implanted with active implantable electronic devices such as cardiac pacemakers/defibrillators, cochlear implants, deep brain stimulators, or drug infusion pumps, or presence of local metal foreign bodies/implants in the area to be implanted; or other contraindications to intracranial implantation as assessed by the investigator;
* Malignancies in other organ systems;
* Cardiovascular system diseases: severe cardiac insufficiency, severe arrhythmias, or uncontrolled hypertension;
* Other ongoing medical interventions that may affect the benefit from BCI intervention (e.g., dependence on ventilator support, tracheostomy, nasogastric tube feeding, etc.);
* Presence of psychiatric or psychological disorders that may interfere with the subject's participation in BCI training, such as depression (HAMD ≥ 18 points) or anxiety disorder (HAMA ≥ 14 points) ;
* Presence of active infection; severe coagulation abnormalities (activated partial thromboplastin time (APTT) or prothrombin time (PT) \> 2.5 × upper limit of normal); or other severe systemic diseases that, as assessed by the investigator, may significantly increase surgical risk or interfere with neurological function assessment or system use;
* Contraindications to surgery or anesthesia, or deemed unsuitable for implantation surgery by anesthesiology/surgical assessment;
* Fever, or vital signs and/or intracranial status not yet stabilized;
* Upper-limb motor dysfunction due to other etiologies, such as amyotrophic lateral sclerosis, syringomyelia, spinal vascular diseases, muscular dystrophy, hypokalemic periodic paralysis, spondylitis, arthritis, osteomyelitis, peripheral nerve injury, tendon rupture, etc.;
* Planned MRI examination during the device implantation period;
* Life expectancy \< 6 months (e.g., severe end-stage diseases);
* Participation in other drug or medical device clinical trials within the past 1 month;
* Pregnant or breastfeeding women;
* Other conditions that, in the investigator's judgment, make the subject unsuitable for participation in this clinical trial.
