Journal CME May 2026: Ultrasonographic evaluation of ulnar innervated muscles in ulnar neuropathy at the elbow-PM R - 2025 - Ogalo - Ultrasonographic evaluation of ulnar innervated muscles in ulnar neuropathy at the elbow

PM R - 2025 - Ogalo - Ultrasonographic evaluation of ulnar innervated muscles in ulnar neuropathy at the elbow

Pdf Summary

This cross-sectional study evaluated whether quantitative muscle ultrasound (qMUS) can validly assess ulnar-innervated intrinsic hand muscles in chronic ulnar neuropathy at the elbow (UNE). Sixteen adults participated: 8 with chronic UNE (all post decompression and reverse end-to-side anterior interosseous-to-ulnar nerve transfer) and 8 healthy controls, with additional contralateral “healthy” limbs included when appropriate.<br /><br />The investigators measured muscle thickness (MT), cross-sectional area (CSA), and echogenicity in the first dorsal interosseous (FDI) and abductor digiti minimi (ADM). These ultrasound measures were compared with compound muscle action potential (CMAP) amplitudes from nerve conduction studies and key pinch strength.<br /><br />Main findings:<br />- FDI MT and FDI echogenicity were significantly correlated with key pinch strength.<br />- Echogenicity showed the strongest relationship with pinch strength and explained more variance than MT.<br />- Echogenicity in both FDI and ADM was significantly and inversely correlated with corresponding CMAP amplitudes.<br />- FDI CSA was not significantly associated with key pinch strength or CMAP.<br />- ADM MT and CSA were positively correlated with ADM CMAP, suggesting muscle-specific differences in how ultrasound measures reflect nerve function.<br /><br />The authors conclude that qMUS, especially echogenicity and MT, provides useful complementary information about muscle health in UNE. Echogenicity may be particularly valuable because it reflects chronic denervation-related fibrosis and fat replacement, which are not captured well by CSA alone. The study supports qMUS as a noninvasive tool for assessing severity and potentially monitoring progression or treatment response in focal entrapment neuropathies.

Keywords

quantitative muscle ultrasound

ulnar neuropathy at the elbow

intrinsic hand muscles

first dorsal interosseous

abductor digiti minimi

echogenicity

muscle thickness

cross-sectional area

compound muscle action potential

key pinch strength