Clinical and Ultrasonographic Bilateral Split Elbow Sign as the Initial and Sole Presentation of Suspected Motor Neuron Disease in a Young Filipino Male: a Case Report

Neuromuscular ultrasound (NMUS) has been recently used to complement nerve conduction study-electromyogram (NCS-EMG) in detecting fasciculations in amyotrophic lateral sclerosis (ALS) but not in characterizing split elbow sign (SES). Here, we report the ultrasound findings of a young Filipino male with SES suspected to have motor neuron disease (MND). A 41-year-old Filipino male came to the clinic for a 3-year history of symmetric, progressive wasting, cramping, and weakness of the elbow flexors. The bilateral anterior arm areas were atrophic with medical research council grade (MRC) strength of 2/5 on the right and 1/5 on the left. The NCS-EMG revealed active and chronic denervation changes only in the bilateral biceps and brachialis. The split elbow phenomenon was confirmed by NMUS showing severe atrophy of the elbow flexors and normal elbow extensors. SES may be a marker of early-onset motor neuron disease and it can be assessed easily and painlessly using neuromuscular ultrasound. Increased echogenicity and relative abundance of fatty tissue in the biceps compared to the triceps may characterize SES in NMUS.