Background: Both chronic and acute pain have been cited as the most common symptoms amongst patients with multiple sclerosis (MS), with recent prevalence estimates as high as 83 %. The evidence for spasticity and trigeminal neuralgia pharmacological treatments in MS has been systematically reviewed, but no equivalent reviews have been published concerning MS pain unrelated to these two conditions.
Objective: Our objective was to systematically review pain management strategies for the reduction of non-spastic and non-trigeminal neuralgic pain in MS patients.
Data sources: Experimental studies published after 1965 were chosen for review by searching electronic databases (e.g. PubMed, Cumulative Index to Nursing and Allied Health Literature, Science Citation Index Expanded, Conference Proceedings Citation Index-Science, and clinicaltrials.gov) and bibliographies/citations of previously published reviews.
Study selection: Studies were included if all participants were adults clinically diagnosed with MS, study sample was not restricted to participants with spasticity or trigeminal neuralgia, and participant-reported pain was a primary or secondary outcome measured with a validated tool.
Study appraisal and synthesis methods: Records were screened and methodological qualities of included studies were assessed independently by two reviewers under the supervision of another reviewer using the principles recommended in the Cochrane Handbook for Systematic Review of Interventions and the levels of evidence espoused by the American Academy of Neurology.
Results: Fifteen studies met the inclusion and exclusion criteria for review; interventions included antidepressants, anticonvulsants, dextromethorphan/quinidine, cannabinoids, and opioids/opioid antagonists. The pooled effect size for anticonvulsants (4 studies, 78 participants) was -1.88 (95 % CI: -3.13 to -0.64). The pooled effect size for cannabinoids (3 studies, 565 participants) was 0.08 (95 % CI: -0.74 to 0.89). Overall, only four trials reported Class 1 evidence. For these trials, dizziness was the most commonly reported adverse event, followed by nausea and somnolence.
Limitations: The relatively small number of trials in MS patients with chronic pain precludes specific recommendations for treatment strategies. The review did not reveal any studies of drug combinations.
Conclusions: More trials with rigorous design and reporting are needed to determine effective treatments for specific pain types presenting in people living with MS.