Peripheral nerve ultrasound in amyotrophic lateral sclerosis phenotypes

Introduction: In this study we sought to determine the cross-sectional area (CSA) of peripheral nerves in patients with distinct subtypes of amyotrophic lateral sclerosis (ALS). Methods: Ulnar and median nerve ultrasound was performed in 78 ALS patients [classic, n=21; upper motor neuron dominant (UMND), n=14; lower motor neuron dominant (LMND), n=20; bulbar, n=15; primary lateral sclerosis (PLS), n=8] and 18 matched healthy controls. Results: Compared with controls, ALS patients had significant, distally pronounced reductions of ulnar CSA (forearm/wrist level) across all disease groups, except for PLS. Median nerve CSA (forearm/wrist level) did not differ between controls and ALS. Conclusion: Ulnar nerve ultrasound in ALS subgroups revealed significant differences in distal CSA values, which suggests it has value as a marker of LMN involvement. Its potential was particularly evident in the UMND and PLS groups, which can be hard to separate clinically, yet their accurate separation has major prognostic implications