Pilot study: Differences in echo intensity ratios between ulnar and median innervated muscles in ulnar neuropathy

Background: This study evaluated muscle echo intensity (EI) ratio in patients with ulnar neuropathy at the elbow (UNE) and healthy controls. Methods: In this prospective study, 28 patients with electrodiagnostically confirmed unilateral UNE and 12 healthy controls were ultrasonographically assessed for EI ratios of the hypothenar and thenar muscles. The affected and unaffected hands between the UNE patients and controls and patient subgroups (subdivided according to electrodiagnostic severity) were compared to determine any significant differences. Results: In patients with UNE, the EI ratio of the hypothenar to thenar muscles was significantly higher for the affected side than for the unaffected side (1.08 ± 0.11 and 0.97 ± 0.18, respectively) or the control group (0.95 ± 0.05). A significant difference in the EI ratio was observed among the subgroups (mild vs. severe subgroup, P < 0.01). Conclusions: Ultrasonographic EI measurement may be a useful parameter in the evaluation and screening of UNE.