Pain and syringomyelia: a review.

The pathophysiological basis of chronic pain syndromes remains poorly defined. Central and dysesthetic pain are probably the most disabling of sensory disturbances associated with syringomyelia, and, unfortunately, effective treatment remains elusive. In this paper, the authors review their institutional experience with both clinical and laboratory studies of patients with syringomyelia, and they review the relevant literature. To date, there is no consensus as to the best treatment for central cord pain syndromes, although there are many promising areas of current research involving the use of neurochemicals in the spinal cord.

Distribution of substance P in the spinal cord of patients with syringomyelia.

The distribution of substance P, a putative neurotransmitter and pain-related peptide, was studied using the peroxidase-antiperoxidase immunohistochemical method in the spinal cords obtained from autopsy of 10 patients with syringo-myelia and 10 age- and sex-matched, neurologically normal individuals. Substance P immunoreactivity was present in axons and in terminal-like processes in close apposition to neurons in the first, second, and third laminae of the dorsal horn. Smaller amounts of peroxidase-positive staining were found in the fifth lamina of the dorsal horn, the intermediolateral nucleus, the intermediomedial nucleus, and the ventral horn. In nine of 10 patients with syringomyelia, there was a substantial increase in substance P immunoreactivity in the first, second, third, and fifth laminae below the level of the lesion. A marked reduction or absence of staining was present in segments of the spinal cord occupied by the syrinx. Central cavities produced bilateral abnormalities, whereas eccentric cavities produced changes that were ipsilateral to the lesion. No alterations in staining were found in the spinal cord of an asymptomatic patient with a small central syrinx. The authors conclude that syringomyelia can be associated with abnormalities in spinal cord levels of substance P, which may affect the modulation and perception of pain.

Dysesthetic pain in patients with syringomyelia.

Dysesthethic pain is a common complaint of patients with syringomyelia, traumatic paraplegia, and various myelopathic conditions. Because cavitary lesions of the spinal cord can be defined with good resolution by magnetic resonance imaging, syringomyelia provides a potential model for examining anatomic correlates of central pain. In this study, a syndrome of segmental dysesthesias, characterized by burning pain, hyperesthesia, and a variable incidence of trophic changes, was described by 51 of 137 patients (37%) with syringomyelia at the time of clinical presentation. Complete magnetic resonance scans, including axial images, demonstrated extension of the syrinx into the dorsolateral quadrant of the spinal cord on the same side and at the level of pain in 43 of 51 patients (84%). Surgical treatment of syringomyelia resulted in the relief or improvement of dysesthetic pain in 22 of 37 patients (59%), but 15 patients (41%) reported no improvement or an intensification of pain despite collapse of the syrinx. Postoperative dysesthetic pain was often a disabling complaint that responded poorly to medical therapy, including analgesics, sedatives, antiepileptics, antispasmodics, and anti-inflammatory agents. In most cases, there was a gradual improvement of symptoms, although six patients continued to complain of pain 24 to 74 months postoperatively. Prompt but transient relief was achieved in two of two patients with regional sympathetic blocks, and prolonged relief was achieved in one patient by stellate ganglionectomy. We conclude that painful dysesthesias can be caused by a disturbance of pain-modulating centers in the dorsolateral quadrant of the spinal cord and have certain causalgia-like features that respond in an unpredictable way to surgical collapse of the syrinx.