Ulnar ‘dive’ may not always identify the median nerve in the forearm

I congratulate Singh et al. in identifying the median nerve in the forearm by following the course of the ulnar artery using ultrasonography 1. In their description, the ulnar artery is observed to take a lateral and deep ‘dive’ from the ulnar nerve towards the median nerve. Normally the ulnar nerve lies between flexor carpi ulnaris and flexor digitorum profundus muscles. A relatively common anatomic variant, that occurs in up to 9% of patients, is the superficial ulnar artery, which results from the persistence of embryonic vessels and is often smaller than a normally positioned ulnar artery 2. The superficial ulnar artery remains superficial to the fascia covering flexor carpi ulnaris throughout its course in the forearm and joins the ulnar nerve just proximal to the wrist (Fig. 1). In such cases, an ulnar artery ‘dive’ does not occur and an alternative strategy would be required to identify the median nerve in the forearm.