A 49-year-old man received prolotherapy in the upper cervical region at a local medical clinic. Immediately after the procedure, he felt a sensation resembling an electric shock in his right upper and lower extremities, and continuously complained of numbness and discomfort in the right hemibody. He visited our clinic a week later. Upon physical examination, there were no signifi cant abnormal fi ndings. Th e visual analog scale was 60 points. T2-weight magnetic resonance images of the cervical spine showed a 0.7 cm sized bright oval spot on the right side of the spinal cord at the level of C4-C5 disc, suggesting spinal cord injury. Th ere were no defi nite electrodiagnostic abnormalities. Digital infrared thermal images showed moderately decreased surface temperature on lateral aspect of the right forearm and dorsum of the right hand compared with the other side. Considering that very rare complications like spinal cord injury may develop after prolotherapy, we suggest that special interventions such as prolotherapy be performed by professional experts.