Pain in patients with multiple sclerosis: a population-based study
Svendsen KB, Jensen TS, Overvad K, Hansen HJ, Koch-Henriksen N and Bach FW;
Commented by , 25 Sep 2003
Background
Pain can be a disabling and medically refractory symptom in MS. The reported prevalence of pain varies considerably (30-90%), presumably due to difference in design and methodology of the studies.
Little is known about the intensity of pain symptoms and effect of treatment in MS, and results have not been compared to a reference group. The current study seeks to enlighten these issues in a population-based study.
Aim
To assess the pain prevalence and impact on daily life in MS patients compared with a normal population.
Methods
The study was conducted as a postal survey. Clinically definite MS patients were identified through the Danish Multiple Sclerosis Registry. The reference group was randomly selected from the same general population, and were age and sex stratified to the MS patients.
The pain questionnaire was focused on pain experienced in the month preceding the assessment, and included acute as well as chronic pain syndromes.
Results
The questionnaires were send to 771 MS patients and 769 reference subjects. 627 (81,3%) of MS patients and 487 (63,3%) of the reference subjects responded.
In the MS group, 73 (11,6%) reported attacks and of these 46 (63%) reported pain during the attack. 356 (56,8%) reported muscle spasms and of these 47,7% reported painful muscle spasms.
The most important results of the study are listed below:
- There was no difference in pain prevalence between responders in the MS group compared with the reference group in the month preceding assessment (79,4% vs. 74,7%)
- There was no association between pain and disease duration in the MS group.
- Pain intensity was significantly higher in the MS group.
- MS patients with pain, more frequently required treatment, and more often reported intake of analgesic drugs for 4 days or more.
- Physiotherapy did not reduce intake of analgesic drugs in the MS group, but MS patients not treated with physiotherapy had a higher consumption of analgesics than the reference group.
- More MS patients reported that pain interfered with daily life ”all the time” (19,3% vs. 7,4%) or ”most of the time” (22,3% vs. 12,0%).
- Dysesthesia was reported more frequently in the MS group (38,1% vs. 12,9%).
Discussion
One of the most interesting conclusions of the study is that MS patients have normal pain prevalence. It is a general conception that MS lesions give rise to irritative symptoms like neurogenic pain, and it is therefore surprising that this is not reflected in the results.
One of the drawbacks of the study is that data does not distinguish sufficiently between central and nociceptive pain and the results could therefore be blurred by methodological problems.
Another methodological pitfall is related to the postal survey, since cognitively impaired MS patients may underreport symptoms, which could explain the lack of association between disease duration and pain.
The study clearly show that pain intensity is higher, treatment is more frequent and substantial, and quality of life measures are poorer, which underlines the importance of focusing on pain in the clinical management of MS patients.