Electrical stimulation using implantable radiofrequency microstimulators to relieve pain associated with shoulder subluxation in chronic hemiplegic stroke.

Objective.  To evaluate the ability to relieve shoulder pain by implanting ceramic-case versions of radiofrequency microstimulators (RFM) in paralyzed shoulder muscles. Materials and Methods.  A 66-year-old man, who had left-sided chronic hemiplegia due to a stroke five years previously, had developed shoulder subluxation resulting in pain. Two RFM devices were implanted, one next to the axillary nerve and one at the motor point of the middle deltoid muscle. Electrical stimulation at both sites was commenced two weeks after implantation for a six-month period. Our evaluation of the effectiveness of the RFM devices has been by measuring pain (using the visual analog scale: VAS), range of motion at the shoulder, strength of the deltoid muscle, degree of shoulder subluxation, and muscle atrophy. Following commencement of stimulation, follow-up evaluations were performed at one, two, three, four, and six weeks, three and six months, and after six months of no stimulation. Results.  During the treatment period of six months of stimulation, the patient's pain had reduced from 70 to 0 on the VAS. At six months after completion of the treatment, pain relief and effective evoked muscle contraction have remained. Conclusion.  Although these results suggest that the feasibility of using RFM devices implanted both epineurally to the axillary nerve and next to the muscle motor point in this one patient, to relieve pain and elicit contraction, further investigation is needed to demonstrate the clinical feasibility of using RFMs for treating poststroke shoulder pain.