MRI of the Wrist

Marcos Loreto Sampaio, MD; Nicholas M. Kolanko, MD


Appl Radiol. 2014;43(10) 

In This Article


The median nerve travels through the carpal tunnel and normally should not present variations in signal or thickness. Main findings in cases of compressive neuropathy (carpal tunnel syndrome) are thickening of the nerve proximal to the entrance of the tunnel with associated increased signal on the fluid-sensitive sequences (Figure 13). However, the findings may not be specific. More recently, diffusion tensor MRI (DTI) has been studied as a new tool for diagnosing neuropathy.[25] The role of MRI in carpal tunnel syndrome is to exclude a potential cause for the symptoms, such as flexor tenosynovitis, or masses/cysts within the carpal tunnel.[26] An incidental bifid median nerve and/or a persistent median artery should also be depicted and reported (Figure 14).[27]

Figure 13.

Carpal tunnel syndrome. (A) Sagittal T2-weighted image with fat suppression reveals thickening of the median nerve proximal to the carpal tunnel (arrow); flexor retinaculum (*). (B) Axial T2-weighted image with fat suppression at the level of the dashed arrow in A. Median nerve with increased signal intensity and marked thickening (arrow) at this level proximal to the carpal tunnel. (C) Axial T2-weighted image with fat suppression at the level of the arrow heads in A. Median nerve (arrow) within the carpal tunnel with increased signal intensity (arrow), mildly bowing the flexor retinaculum. Observe the discrepancy of the nerve thickness in relation to B.

Figure 14.

Bifid median nerve. Axial PD-weighted image with fat suppression at the level of the carpal tunnel reveals bifid median nerve (arrows) with persistence of the median artery and veins (dashed arrow).

MRI after carpal tunnel release is sometimes indicated to evaluate recurrence of symptoms. Normal postoperative findings include a complete surgical defect of the flexor retinaculum and volar extrusion of the carpal tunnel components through it, with improvement of neural signal changes. Persistent altered neural thickness may be seen (Figure 15).[28] Rarely, median nerve lipomatosis (fibrolipomatous hamartoma) is detected in the investigation of macrodystrophia lipomatosa or carpal tunnel syndrome.[29,30] In these situations the nerve presents a "spaghetti-" or "multi-cable-like" appearance, with thickened fascicles and prominent fatty interstitial tissue.

Figure 15.

Recurrent neuropathy after carpal tunnel release. Axial PD-weighted image with fat suppression at the level of the carpal tunnel. The surgical defect of the flexor retinaculum is seen (arrow). The median nerve presents increased signal intensity and thickness and there is no extrusion of the carpal tunnel contents through the defect.

The ulnar nerve travels through the canal of Guyon (ulnar nerve tunnel) along the ulnar aspect of the wrist and is the most ulnar structure in the canal, in close proximity to the pisiform and hook of the hamate. Neuropathy may be associated with ganglia and masses within the tunnel, compression due to accessory muscle slips around the nerve, or even fractures or stress injuries of the hook of the hamate (Figure 16).[31]

Figure 16.

Compressive ulnar neuropathy. (A) Axial PD-weighted sequence with fat suppression at the level of the canal of Guyon's. The ulnar nerve (arrow) has high signal intensity and it is thickened. There is a ganglion cyst (*) compressing the ulnar nerve against the pisiform. (B) The ganglion cyst (*) is large and extends distally beyond the ulnar tunnel (hook of the hamate **).