The investigators have recently shown in incomplete SCI patients that long-term paired associative stimulation is capable of restoring voluntary control over some paralyzed muscles and enhancing motor output in the weak muscles. In this study, the investigators will administer long-term paired associative stimulation to patients with incomplete cervical level SCI at the subacute stage, and investigate its effectiveness for upper extremity rehabilitation.

Inclusion Criteria:

1. SCI caused by an external trauma or SCI caused by nontraumatic non-progressive disease of the spinal cord
2. Cervical level injury, tetraplegia
3. Time from injury/onset of symptoms 1-4 months
4. Medical condition stable
5. Residual neural connectivity in upper extremity: some voluntary activity in finger muscles or MEPs obtainable from distal hand muscles

Exclusion Criteria:

1. Diagnosed brain damage, visible in MRI or CT.
2. No activity in hands/fingers and no MEPs recorded from distal hand muscles.
3. Epilepsy
4. Metal inclusion in the head area
5. High intracranial pressure
6. Pacemaker
7. Implanted hearing device
8. Progressive diseases of spinal cord or brain (e.g. malignant tumors, degenerative diseases).
9. History of malignant tumor within the past 5 years.
10. Previous head or spinal cord injury affecting the motor performance of upper extremities.
11. Congenital anomaly in the anatomical structure of spinal canal/cord or dura.
12. Significant systemic disease or other condition that could cause neurological deficit, or may affect subject's capability to undergo investigation-related procedures.
13. Acute severe infection.
14. Contraindications for MRI.
15. Current severe psychiatric diseases.
16. Current chronic drug and/or alcohol abuse.
17. Pregnancy.
18. Severe emergency care polyneuropathy
19. Pressure ulcer affecting the subject's capability to undergo the procedure safely