Penetrating trauma limited to the ulnar artery may also secondarily cause nerve injury from compression by the formation of a space occupying pseudoaneurysm. Acute injuries can be assessed with US to determine the location of nerve injury and if any structure (bone fragment, foreign body) is impinging the nerve ( 6). Ulnar mononeuropathies at the wrist/palm can be divided into acute and chronic etiologies.
However, it is now possible to non-invasively visualize the contents of Guyons canal and the small branches of the distal ulnar nerve which will be discussed in this review. Relatively few cases of ulnar neuropathy at the wrist have been studied with US as the disorder is rare and sonographic evaluation of nerve a fairly recent development. In carpal tunnel syndrome, a formal evidence based guideline has established the accuracy of sonographic diagnosis (Level A) ( 5). US has also been shown to be helpful in cases of electrically non-localizable ulnar mononeuropathy at the elbow ( 4). In addition, these studies show that when using electrodiagnostic studies in conjunction with US, sensitivity is 93.3–98% ( 3). Specifically in ulnar mononeuropathy at the elbow it has been shown to have a sensitivity and specificity in the 74–76 and 72%, respectively ( 2, 3). In a study of all ulnar neuropathies it was shown that in 74% of 281 cases, ultrasound (US) contributed to the evaluation in one of three categories: (1) uncovering a diagnosis not established by the electrodiagnostic testing, (2) enhancing the diagnosis by providing additional information regarding localization or predisposing anatomy, or (3) providing independent confirmation of the diagnosis ( 1).įurther support for the use of US for ulnar neuropathy at the wrist, comes from other studies showing US to be sensitive and specific in the workup of mononeuropathies in general. Imaging can enhance localization and, additionally, demonstrate the presence or absence of focal anatomic lesions along the course of the nerve. Although electrodiagnostic testing can often localize the injury distal to the forearm and assess electrophysiologic severity, it provides limited information regarding etiology.
Ulnar mononeuropathy in the wrist and palm is uncommon but has a multitude of causes including trauma, occupational stressors, sports hazards, intrinsic, and extrinsic anatomical compression, and secondary effects of assistive devices. Furthermore, ultrasound is useful as a patient educational tool to promote behavioral changes that assist in nerve recovery when pathology is related to repetitive stress. The value of using US in conjunction with electrodiagnostic testing is emphasized as the two tests together provide critical information regarding etiology, predisposing factors, and functional significance. In this review, we describe the basic anatomy and the sonographic appearance of the nerve in the wrist and palm in normals and individuals with pathology. The electrophysiologic features of this disorder have been well-characterized, but the sonographic anatomy of the nerve across the wrist and palm has yet to be systematically described in normal and abnormal states. 2Department of Neurology, Wake Forest School of Medicine, Winston-Salem, NC, United Statesįocal ulnar neuropathy at the wrist is a rare but problematic disorder often associated with the unique anatomy of this nerve as it courses through Guyon's canal, a superficial fibro-osseous tunnel in the proximal ulnar palm.
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