Ultrasonographic evaluation reveals thinning of cervical nerve roots and peripheral nerves in spinal and bulbar muscular atrophy

Background Ultrasonography (US) is a noninvasive and patient-friendly tool for the evaluation of peripheral nerves. In motor neuron diseases, amyotrophic lateral sclerosis (ALS) has been reported to show the atrophy of peripheral nerves on US. However, the US findings are still unclear in spinal and bulbar muscular atrophy (SBMA), an adult-onset lower motor neuron disease caused by an abnormal CAG repeat expansion in the androgen receptor gene. Methods We prospectively recruited and evaluated 11 patients with genetically confirmed SBMA and 9 patients with ALS diagnosed according to the revised El Escorial ALS criteria or the Awaji electrodiagnostic criteria. The C5-C7 cervical nerve roots and the median and ulnar nerves were evaluated ultrasonographically. Results The cross-sectional areas (CSAs) of the C6 and C7 nerve roots, the median nerve in the upper arm and forearm, and the ulnar nerve in the upper arm were smaller in patients with SBMA than those in patients with ALS (p < 0.05), whereas the CSAs of the C5 nerve root and the ulnar nerve in the forearm were not smaller Conclusions US showed that the peripheral nerves in patients with SBMA were thinner than those in patients with ALS despite similar degrees of weakness and motor neuron loss. Possible causes include additional sensory nerve involvement and longer disease duration in patients with SBMA than those in patients with ALS.

Automated summary

In this study, peripheral nerves in patients with spinal and bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS) were evaluated using ultrasonography. The results showed that despite similar disease severity and motor neuron loss, the peripheral nerves in SBMA patients were thinner than those in ALS patients.