Beyond motor neurons: autonomic dysfunction and ECG findings in adults with 5q-spinal muscular atrophy

5q-Spinal muscular atrophy (SMA) is a lower motor neuron disease. However, peripheral organ involvement might contribute to its complex clinical picture, especially in severe forms. This study evaluated frequency and characteristics of autonomic symptoms, prevalence of electrocardiographic (ECG) abnormalities, and the impact of autonomic dysfunction on quality of life (QoL) in adults with SMA.

Autonomic function was assessed using the SCales for Outcomes in PArkinson's disease-Autonomic Dysfunction (SCOPA-AUT). 12-Lead ECG was recorded. The Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM), Fatigue Severity Scale (FSS), Beck Depression Inventory (BDI), and 36-Item Short Form Health Survey (SF-36) were collected to assess motor function, fatigue, depression, and QoL.

Forty-three SMA patients (23 males; mean age: 37.6 ± 14.1 years) and forty-three age- and sex-matched healthy controls were included. Compared to healthy controls, SMA patients scored worse on gastrointestinal domain (2.9 ± 2.9 vs. 1.1 ± 1.5, p < 0.001) and in total SCOPA-AUT score (9.8 ± 7.3 vs. 5.7 ± 4.4, p = 0.002). More severely affected patients reported a greater burden of autonomic symptoms compared to those with milder phenotypes. Burden of autonomic symptoms correlated with QoL (ρ = - 0.33, p = 0.028). The presence of major ECG abnormalities showed a negative correlation with SMA type (ρ = - 0.39, p = 0.027), age at the time of testing (ρ = - 0.45, p = 0.009), and ambulatory status (ρ = - 0.39, p = 0.027).

Adults with SMA demonstrate a substantial burden of autonomic symptoms, especially those with more severe disease. This burden significantly compromises patients' QoL. Further studies are needed to better understand autonomic dysfunction in this population.