[Percutaneous epidural electrical stimulation of the spinal cord for intractable pain--with special reference to deafferentation pain]

In a study of 44 patients with different types of chronic pain, mostly associated with deafferentation, chronic percutaneous epidural spinal stimulation has proved useful treatment achieving an initial 52% incidence of pain amelioration overall. Long-term result showed at six months in 86%, at 1 year in 90%, although technical problems, which included electrode displacement and required minor operative readjustment, affected 48% of those permanently implanted. No other complications were seen. Success bore no relationship to quality of pain reported by the patients or to duration of pain. The patients with denervation caused by nerve or root lesions responded better than those with cord lesions even though electrical paresthesia were delivered to the area of pain in each case. A decline in effectiveness with time was noted in small numbers of our cases despite persistence of paresthesia in the area of pain. It is suggested that late failure reflects plasticity of the nervous system in adapting to new inputs. Morphine study was carried out in some of these patients. Morphine did not help to ameliorate the pain in many cases with deafferentation pain. And also Naloxone was administered during successful pain-relieving stimulation. This did not result in recurrence of pain. The Somato Sensory Responses were recorded in 25 patients before and during neurostimulation. When stimulation was applied the late component was suppressed in most of those who enjoyed a good result. The early component was not changed in those patients even during stimulation. These results suggest that spinal cord stimulation would suppress the denervative hypersensitivity of dorsal horn in the patients with deafferentation pain.(ABSTRACT TRUNCATED AT 250 WORDS)