Is Electrical Stimulation Therapy Effective for Pain Relief in MS?

Electrical stimulation therapy (EST) provides pain relief, especially in the medium-term, in people with multiple sclerosis (MS), according to a systematic review and meta-analysis published in the journal Multiple Sclerosis and Related Disorders.

Many people living with MS experience pain, of different types and in different body regions. Many receive EST to treat such pain. EST’s tolerable side effect profile, compared to that of many pain medications, makes it a particularly appealing modality. However, there is limited quantitative evidence regarding its efficacy in MS. Also, it is unclear whether EST improves pain-related quality of life or disability, or related neuropsychiatric symptoms such as fatigue and depression.

For this study, researchers analyzed randomized, controlled trials (RCTs) comparing EST to either placebo or another therapy for MS-related pain. A total of 10 trials with 315 patients met criteria for both systematic review and meta-analysis. From these, the team extracted data on measured outcomes, risk of bias for each study, and strength of evidence for each outcome.

Across all studies, patients had been diagnosed with relapsing-remitting, secondary-progressive, and primary-progressive MS. They had a variety of pain presentations, including stable low back pain, upper extremity pain, neuropathic pain, and central pain. They received various forms of EST:

• transcranial direct current stimulation,
• transcutaneous electrical nerve stimulation,
• transcutaneous spinal direct current stimulation,
• transcranial random noise stimulation, and
• electroacupuncture.

The researchers found that EST reduced visual analogue scale (VAS) scores of pain intensity, when pooled across all types of EST in 8 of the studies (mean difference (MD), − 1.75, 95% CI, -2.85 to -0.64; P =.002). This effect was statistically significant for medium-term treatment across 2 pooled studies (MD, -2.17, 95% CI, – 3.51 to -0.84; P =.001), but not for short- or long-term treatment. Immediately post-treated, compared with transcranial direct current, electroacupuncture greatly lowered VAS scores.

High heterogeneity in pain intensity outcomes across the aggregated studies (I² = 73%) was attributed to variability in type, frequency, duration, and intensity of EST.

EST did not influence pain-related quality of life, measures of depression and of fatigue, or impairment related to low back pain. Mild side effects included headache, nausea, and insomnia; but no study reported any major adverse events.

A total of 2 studies showed low risk of bias. Overall, risk of selective reporting of results and publication bias were low. Across all outcomes, strength of evidence ratings ranged from moderate to very low.

The estimates of treatment efficacy, in the researchers’ opinion, may have been overly low because of the small total sample size, high overall study heterogeneity, and short follow-up periods. The small sample also likely raised the risk of bias. Other likely sources of bias included inadequate randomization protocols and incomplete blinding of outcome assessment.

The researchers further suggested that future studies of EST interventions in MS should include measures of MS-relevant motor dysfunction (eg, ataxia, tremor).

“Additional research with rigorous assessment criteria and high-quality RCT designs is needed to verify the impact of EST on MS,” they concluded.