High Resolution Ultrasound in Entrapment Neuropathies of Ulnar Nerve- A Case Series

Ulnar nerve is one of the terminal branches of the medial cord of brachial plexus. Owing to its superficial location and unprotected course ulnar nerve is susceptible to physical impingement at specific sites. Although clinical and electrophysiological assessment can diagnose ulnar neuropathy and site of compression, they do not provide aetiological information which is important for management. High Resolution Ultrasonography (HRUS) is a non invasive imaging tool that has been used widely to evaluate peripheral nerves. In this case series, HRUS imaging findings in seven distinct cases of entrapment of ulnar nerve or its branches are presented. In cases 1, 2, 3 and 4, ulnar nerve was entrapped at the elbow; by synovial thickening due to degeneration, claw osteophyte arising from ulna, synovial cyst and epineural ganglion cyst respectively. In cases 5 and 6, ulnar nerve was entrapped at the wrist by a pisotriquetral ganglion cyst and an ulnar artery pseudoaneurysm respectively. In case 7 the Dorsal Cutaneous Branch (DCB) of ulnar nerve was entrapped over the Extensor Carpi Ulnaris (ECU) tendon. In all the aforementioned cases, HRUS accurately identified the site of entrapment, the status of ulnar nerve and the underlying cause of entrapment, which was subsequently confirmed surgically. The non invasive, inexpensive and accurate qualities make HRUS a potential first line imaging tool in the evaluation of entrapment neuropathies of superficial nerves.