P.108 Clinical and electrophysiological evaluation of fatigue in adult patients with spinal muscular atrophy (SMA)

Abstract

Fatigue is common in SMA, and negatively interferes with quality of life of affected individuals, especially in repetitive daily activities. Despite that, few studies assessed potential electrophysiological correlates of fatigue in late-onset SMA. To assess fatigue severity and its correlation with neuromuscular jitter in a cohort of 25 adult patients with SMA. Fatigue was quantified with 2 scales: the modified fatigue impact scale (MFIS) and the fatigue severity scale (FSS). Simultaneously, concentric needle evaluation of the stimulated jitter in the frontalis muscle was performed. Jitter was expressed as the mean of mean consecutive differences (MCD) in at least 100 potentials. Three distinct MCDs were obtained in each evaluation. The motor function measure (MFM), expanded Hammersmith motor functional scale (HFMSE) and revised upper limb module (RULM) scales were used to assess motor function in each individual. There were 16 men and 9 women, with a mean age of 33.4 years. Mean MFM, HFMSE and RULM scores were 46.59, 21.08 and 22.82, respectively. Regarding fatigue, mean FSS and MFIS physical scores were 3.1 (max possible of 7) and 20 (max possible of 36). Considering an upper normal limit of 28 us, thirteen subjects had abnormal jitter results (mean=32.69us), whereas 12 had normal results (mean=17.97us). The proportion of patients with abnormal jitter was significantly higher among patients with more severe fatigue (FSS score>4) compared to those with less severe fatigue (FSS score<4) (p=0.04). Although preliminary, these results indicate that neuromuscular junction failure may play a role in SMA-related fatigue and jitter may be a neurophysiological marker to assess fatigue in this condition.