Split hand muscle echo intensity index as a reliable imaging marker for differential diagnosis of amyotrophic lateral sclerosis

Objective The objective of this study was to investigate the usefulness of muscle ultrasound in evaluating dissociated small hand muscle atrophy, termed € split hand', and its feasibility in the diagnosis of amyotrophic lateral sclerosis (ALS). Methods Forty-four patients with ALS, 18 normal subjects and 9 patients with other neuromuscular disorders were included in this study. The hand muscles were divided into three regions, the median-innervated lateral hand muscle group (ML), the ulnar-innervated lateral hand muscle (UL) and the ulnar-innervated medial hand muscle (UM), and the muscle echo intensity (EI) and compound muscle action potential (CMAP) were measured. We calculated the split hand index (SHI) using muscle EI (SHI mEI) and CMAP (SHI CMAP) for comparison among groups. The SHI was derived by dividing muscle EI (or CMAP) measured at the ML and UL by that measured at the UM. Results The SHI mEI was significantly higher in patients with ALS (51.7±28.3) than in normal controls (29.7±9.9) and disease controls with other neuromuscular disorders (36.5±7.3; P<0.001), particularly in upper limb-onset ALS (66.5±34.0; P<0.001). Receiver operating characteristic curve analysis indicated that the SHI mEI had significantly better diagnostic accuracy than the SHI CMAP. Conclusions The SHI mEI was more sensitive in evaluating dissociated small hand muscle atrophy compared with the SHI CMAP and may be a reliable diagnostic marker for differentiating ALS from other neuromuscular disorders and healthy controls.