A study by researchers at Bambino Gesù Children’s Hospital in Rome, Italy, found evidence that spinal muscular atrophy (SMA) patients may develop sensory neuropathy as they age. Previous anecdotal evidence of sensory electrophysiological changes had been seen in pediatric SMA type 1 patients, however, little was known about how these changes related to the children’s ages.
During the research, sensory nerve conduction studies of the sural and median nerves were performed in SMA patients and healthy subjects from a range of ages. The study results, published in Muscle & Nerve, showed that sensory nerve action potential (SNAP) amplitudes in the sural and median nerves appeared to decrease in SMA patients as they age when compared to healthy subjects.
The investigators did not find a significant difference in the SNAP amplitude declines between the upper and lower limbs of patients. SNAP amplitudes in younger SMA patients were similar to those found in healthy subjects.
According to the study’s authors, “Our data suggest that sural and median nerve SNAP amplitudes are normal in younger patients, while an axonal neuropathy appears in older ones.”
A total of 28 patients of different ages with SMA type 1 were recruited for the study. For comparison, 93 healthy subjects stratified by age were also recruited. As part of the study, SNAP amplitudes and sensory nerve conduction velocities were recorded from the median and sural nerves in each patient and healthy subject. SNAP amplitudes were similar between younger patients and healthy subjects. In older patients, however, the amplitudes appeared to decrease in comparison to the age-matched healthy subjects.
SMA is a rare genetic disorder that primarily affects motor neurons and leads to progressive muscle weakness, respiratory failure, and often premature death. SMA follows an autosomal recessive inheritance pattern and is caused by mutations in the survival motor neuron 1 (SMN1) gene. Three disease-modifying therapies have been approved for the treatment of SMA, including Spinraza® (nusinersen), Zolgensma®(onasemnogene abeparvovec-xioi), and Evrysdi® (risdiplam).
Pro S, Tozzi AE, D’Amico A, et al. Age‐related sensory neuropathy in patients with spinal muscular atrophy type 1. Muscle Nerve. Published online August 8, 2021. doi:10.1002/mus.27389