Fig. 5

Compression neuropathy of the superficial and deep branches in a 62-year-old amateur cyclist with sensory numbness in the territory of the ulnar nerve. a, b, c, d Consecutive short-axis 18–5-MHz US images show mild edematous changes affecting the deep branch fascicles (arrowhead) at the level of the pisiform (Pis), with a normal appearance of the superficial branch (outlined arrowhead). In this area, the ulnar artery (outlined arrow) appears normal. b Between the pisiform and the hamate, the superficial branch has an anomalous path underneath the abductor digiti minimi (ADM). Note the thickening of the ulnar artery walls as it crosses the edematous subcutaneous tissue of the hypothenar eminence. c At the hamate hook (HH) the superficial branch crosses (dashed arrow) from deep to superficial the proximal part of the flexor digiti minimi (FDM). d At the base of the V metacarpus (V met) the deep branch presents a normal appearance as it runs between the flexor digiti minimi and the opponens digiti minimi (ODM) whereas the superficial branch appears swollen as it crosses the edematous subcutaneous tissues. Note the thrombosed ulnar artery on the radial side of the superficial branch. Arrow, median nerve; thin arrows, flexor retinaculum; APB, abductor pollicis brevis; Ft, flexor tendons; asterisk, pisohamate ligament