Deep Pain Loss in Syringomyelia and Other Spinal Cord Lesions

Abstract

Deep pain is an important muscle nociception; however, testing for it has long been ignored in the clinical field. The authors studied the clinical significance of testing deep pain sensation in patients with spinal cord lesions. Deep pain sensations evoked by squeezing superficial muscles were examined in 19 patients with syringomyelia, 50 with cervical spondylosis, 2 with Hirayama disease, and 2 patients with spinal neurinoma. Deep pain sensitivity was graded as hyper-, normal, hypo-, and loss compared to that of the trapezius muscle in the intact side and was compared with other neurological findings. In those patients with syringomyelia, deep pain was diminished or lost in 14 (74%) patients. Only 24% of the patients with cervical spondylosis presented superficial sensory loss in the digits. In contrast, 70% presented deep pain diminution, especially in those muscles with diminished deep tendon reflex (except for Hirayama disease) or in those muscles innervated by the same segment with a dysesthetic dermatome. In the patients with spinal neurinoma, deep pain was lost in those muscles with diminished deep tendon reflex. Ten patients of 17 with syringomyelia underwent surgery and complained of residual pain postoperatively in spite of shrinkage of the syrinx. This residual pain was of two types, one being superficial dysesthetic pain and the other muscle aching pain. The latter presumably is related to the dysfunction of the system conveying muscle nociception. Deep pain loss is not uncommon in many spinal cord lesions. In addition, postoperative residual pain in syringomyelia should be recognized as superficial dysesthetic pain, deep muscle aching pain, or both. This approach will develop a successful measure of treatment of residual pain in the future.