A Role for Cannabinoids in the Treatment of Myotonia? Report of Compassionate Use in a Small Cohort of Patients

Background: The symptomatic treatment of myotonia and myalgia in patients with dystrophic and non-dystrophic myotonias is often not satisfactory. Some patients anecdotally report symptoms' relief through consumption of cannabis.

Methods: A combination of cannabidiol and tetrahydrocannabinol (CBD/THC) was prescribed as compassionate use to six patients (four patients with myotonic dystrophy types 1 and 2, and 2 patients with CLCN1-myotonia) with therapy-resistant myotonia and myalgia. CBD/THC oil was administered on a low dose in the first 2 weeks and adjusted to a higher dose in the following 2 weeks. Myotonia behaviour scale (MBS), hand-opening time, visual analogue scales (VAS) for myalgia and myotonia, and fatigue and daytime sleepiness severity scale (FSS, ESS) were performed weekly to monitor treatment response.

Results: All patients reported an improvement of myotonia especially in weeks 3 and 4 of treatment: MBS improved of at least 2 points in all patients, the hand-opening time variously improved in 5 out of 6 patients. Chronic myalgia was reported by both DM2 patients at baseline, one of them experienced a significant improvement of myalgia under treatment. Some gastrointestinal complaints, as abdominal pain and diarrhoea, improved in 3 patients; however, 4 out of 6 patients reported new-onset constipation. No other relevant side effect was noticed.

Conclusions: These first empirical results suggest a potentially beneficial role of CBD/THC in alleviating myotonia and should encourage further research in this field including a randomized-controlled trial on larger cohorts.