Diagnostic neuromuscular ultrasound to confirm clinical significance of a genetic variant for Charcot-Marie-Tooth type 4C: A case report.

Abstract

Neuromuscular ultrasound (NMUS) has emerged as a beneficial, complementary tool to EMG in the diagnosis of neuromuscular diseases as it provides high-resolution anatomic imaging of peripheral nerves and muscles. It has been used previously as an adjunct to EMG to diagnose Charcot-Marie-Tooth disease (CMT). Here, we present a case of a 64-year-old male with bilateral sensorineural hearing loss of 14 years who presented to an outpatient neuromuscular clinic at a tertiary medical center with very slow progressive paresthesias. This case highlights the application of NMUS to help confirm the presence of a likely CMT type 4C despite indeterminate genetic testing results and challenging EMG results. He had genetic testing which revealed a normal PMP22 gene; however, he had a variant of uncertain significance (VUS) in the SH3TC2 gene which has shown associations with autosomal recessive CMT4C. NMUS revealed mild median and significant tibial nerve uniform enlargement throughout their course. There may also be utility in performing NMUS on similarly affected family members if the same VUS returns for SH3TC2, with consideration of both peripheral nerve and nerve root assessment.