Guyon Tunnel

Proximal to the carpal and Guyon tunnels, the median and ulnar nerves are recognized based on their peculiar fascicular echotexture. Approaching the wrist, the median nerve becomes more superficial and lateral and then runs toward midline and in a deeper position to enter the carpal tunnel (JAMADAR et al. 2001). The palmar cutaneous branch of the median nerve arises from its palmar-radial quadrant approximately 5 cm cranial to the proximal wrist crease (Taleisnik 1973). It remains bound at the main nerve trunk to leave it after approximately... 

The Guyon tunnel is located in a medial and superficial position relative to the carpal tunnel. It is delimited hy the dorsal aspect of the transverse carpal ligament and the superficial palmar carpal ligament on the radial side, and hy the lateral aspect of the pisiform on the ulnar side. The transverse carpal ligament and the pisiform are easily detected with US. On the contrary, the superficial palmar carpal ligament is very thin and difficult to visualize. Once the curvilinear shape of the pisiform is found, care should he taken to identify the ulnar... 

Similar to the dorsal wrist, tendinopathies of the flexor tendons are commonly encountered, most often at the insertion of the flexor carpi radialis tendon and within the carpal tunnel for the flexor digitorum tendons (Fig. 10.33b) (Daenen et al. 2004). In addition to tendinopathies, compression neuropathy of the median nerve at the carpal tunnel is the leading pathology of the wrist as regards prevalence of disease and clinical relevance. The entrapment of the ulnar nerve at the Guyon tuimd is rare and, in many cases, secondary to other disorders. 

Compared with carpal tunnel and cubital tunnel syndrome, ulnar neuropathy at the Guyon canal is rare. 

Figure 106. Common sites of ulnar nerve entrapment. A, arcade of Struther B, cubital tunnel C, flexor carpi rdnaris D, Guyon s turmel.

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