Pain in adult and adolescent patients with 5q-associated Spinal Muscular Atrophy – an often underrated phenomenon

Background: Spinal muscular atrophy (SMA) is a genetic disorder leading to progressive muscle weakness and atrophy. Pain in SMA may be the consequence of the underlying neuromuscular disease but has hardly been investigated so far. Objective: To assess pain in SMA and its interaction with patient's wellbeing. Methods: In a prospective, cross-sectional study design, 70 adult and adolescent SMA patients (median age 30 years, IQR 21–49 years, types I-IV) were assessed at the Department of Neurology, Ulm University hospital. Pain was evaluated with a self-adapted Pain Scale, depressiveness with the ALS-Depression-Inventory-12-Items (ADI-12) and global Quality of Life (gQoL) with the Anamnestic Comparative Self-Assessment (ACSA). Results: We found an intermittent frequency of pain in 80% in SMA patients with more than half of the patients experience pain at least once a week. The mean pain intensity score estimated by pain frequency and strength was 24 on a scale of 0 to 240, indicating a frequently appearing mild to moderate pain. Pain was mostly located in the lumbar spine, hip, and thoracic spine. The pain intensity score was independent from demographics (age, gender) or clinical parameters (SMA type, physical state), but, instead, it was associated to depressiveness. Depressiveness was more prevalent in older SMA patients. gQoL was rather independent from pain intensity or physical state. Conclusions: The study provides evidence for a prevalence of mild to moderate pain in 80% of adult and adolescent SMA patients. Pain was not simply caused by physical deficits and did not severely interfere with patients’ quality of life, but, instead, was closely interrelated with patients’ affective state.