A Nationwide Survey of Spinal Cord-Related Pain Syndrome in Japan: Clinical Characteristics and Treatment

Introduction: In this study, we defined chronic neuropathic pain (NeP) in patients with diseases associated with spinal cord damage, such as spinal cord-related pain syndrome, and performed a nationwide survey investigating the prevalence, actual status, and features of this syndrome in Japan in order to gather basic information needed for planning control measures. Methods: In this nationwide epidemiologic survey, a mail-in questionnaire was sent to 3,206 institutions throughout Japan certified by the Japanese Orthopaedic Association (2,065 institutions) and the Japan Neurosurgical Society (1,141 institutions). The survey included the number of patients, frequency, and type of allodynia, concomitant diseases, and types of and responses to treatment. Results: Valid responses were obtained from 552 institutions on 3,401 patients. Of these, 1,719 (50.5%) patients experienced no pain, and thus the study involved the analysis of data of the remaining 1,682 patients with pain. The most frequent underlying conditions were cervical spondylotic myelopathy (26.7%), spinal cord injury (17.4%), and ossification of the posterior longitudinal ligament (OPLL) of the cervical spine (14.1%). Among the 1,682 patients, 62.5% reported at-level pain, among which 43.0% presented with allodynia. On the other hand, 38.7% presented with below-level pain. The majority of patients (73.4%) used nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants (46.6%). The effectiveness of treatment was significantly higher in patients using anticonvulsants (31.1%) than in those using other medications. About a third of the patients stopped the treatment for either lack of effect or adverse effects. Conclusions: The characteristics of NeP in patients with spinal cord-related pain syndrome varied according to its level in relation to the affected spinal segment (at-level and/or below-level). Unfortunately, medications are sometimes ineffective and have potential adverse effects. Further classification of allodynia is needed for effective symptom-based treatment.