Abstract
Introduction
Approximately 80% of the patients with spinal cord injury (SCI) suffer from neuropathic pain. Some methods exist for evaluating neuropathic pain, but they have not been rigorously validated. Here, we characterized the neuropathic pain occurring after SCI using a validated self-questionnaire that assesses different types of pain.
Patients and Methods
Seventy-two patients at least 3 months after SCI were registered in this study. The patients included 66 males and 6 females, in the age group of 20 to 79 years (mean: 56 years). The questionnaire consisted of the Neuropathic Pain Symptom Inventory (NPSI) (Bouhassira et al, Pain, 2004) and the Short Form (SF)-36 Health Survey. Within the NPSI scoring system, the subscores for burning (superficial) spontaneous pain, pressing (deep) spontaneous pain, paroxysmal pain, evoked pain, and paresthesia/dysesthesia were determined (10 possible points for each subscale, with a possible total of 50). The NPSI scoring system was previously validated in reports that examined the neuropathic pain after herpes, and associated with spinal cord tumor and carpal tunnel syndrome. Neurological deficits were evaluated by the American Spinal Injury Association (ASIA) grade. Correlations between the NPSI score and the location of the central neuropathic pain (at injury level and/or below injury level), ASIA grade, and SF-36 scores were investigated.
Results
The mean total NPSI score was 13.0 and the NPSI subscore for paresthesia/dysesthesia (3.8) was significantly higher than that for the other subscales (Fig. 1). When compared to injury site, the subscore for paresthesia/dysesthesia was significantly higher in cervical SCI (p = 0.0146), whereas there was no significant difference among the subscores in thoracic or lumbar injury. When compared to the location of the neuropathic pain, the total NPSI score was significantly higher in patients with pain below than with pain at injury level (p = 0.0300). The NPSI score was also significantly higher in patients with ASIA grade B (Fig. 2), and the patients with ASIA grade B presented more frequently with pain below than with pain at injury level. In an analysis of each SF-36 subitem score versus the NPSI score, body pain, general health, and mental health showed a significant negative correlation with the NPSI score.
Conclusion
In this study, paresthesia/dysesthesia was the most common complaint for patients with chronic SCI. A similar result was previously obtained in patients with spinal cord tumor, suggesting that paresthesia/dysesthesia is the main characteristic of neuropathic pain in the spinal cord. Patients with ASIA grade B were more likely to complain of intense pain below the injury level than those with other grades. Pain below the injury level is thought to originate from an injury of the spinothalamic tract in the spinal cord. Therefore, the neuropathic pain in patients with ASIA grade B may be related to damage and degeneration of the spinothalamic tract. Finally, neuropathic pain was significantly correlated with the health-related quality of life, indicating the importance of controlling the neuropathic pain in patients with SCI.
