The goal of this study was to evaluate the efficacy and safety of ITZ in patients with harmful refractory neuropathic pain following spinal cord lesions.

This study was designed as a prospective cohort of twenty patients with pain following spinal cord injury (SCI) of various etiologies (post-traumatic, postsurgical, ischemic syringomyelia). Primary endpoint is the number of patients responders to the ITZ tests. Secondary endpoints is the assessment of long-term efficacy and study of impact on different features of pain and changes in antalgic medications. The efficacy of the drug was tested initially by lumbar bolus injection (1 to 2.5 mcg) and/or continuous lumbar infusion using external pump (increased progressively max 10 mcg/d). Patients were considered responders if>40% reduction from baseline visual analogic scale (VAS) was observed without side effects. Pump placement with continuous intrathecal infusion was then proposed. Detailed analyses of test failures were performed in order to identify reasons for lack of efficacy.

Overall out of twenty patients tested, fourteen were considered responders to test (70%). Only eleven of them (55%) benefited from a permanent pump implantation without any side effects. Pump were followed up on average for 3.59 years (± 1.94). The absolute value of pain on VAS significantly decreased between baseline and last follow-up from 7.91 to 4.31 with an average decrease of more than 3 points (45.5% P=0.02 Wilcoxon rank sum test). After pump implantation, minor increases in CPK levels have been noted in three patients.

This pilot study shows significant decrease of pain after ITZ for well selected patients with SCI in whom other antalgic options are not available. This study includes a short population but is encouraging as facing with one of the most difficult to treat neuropathic pain. Further study with randomized controlled design is ongoing.