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Ulnar neuropathies: where, why, and what to do?
  1. John Stewart
  1. Consultant Neurologist, Lions Gate Hospital, North Vancouver, British Columbia, Canada
  1. Correspondence to:
 Dr J Stewart, 204-145 East 13th Street, North Vancouver, BC V7L 2L4, Canada;
 john.stewart{at}telus.net

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Ulnar neuropathy alert by Auguste Rodin

Diagnosing and treating ulnar neuropathy is not nearly as straightforward as carpal tunnel syndrome. Here I will attempt to guide the busy practical neurologist to make the diagnosis with confidence and to manage patients effectively. There are four critical questions to be considered in a patient with a possible ulnar neuropathy:

  • is it really an ulnar neuropathy?

  • where is it: elbow or wrist?

  • if at the elbow, how to treat: conservatively or with surgery?

  • if not an ulnar neuropathy, what is it: C8 or T1 radiculopathy, plexus lesion, spinal cord lesion, anterior horn cell lesion, other?

ANATOMY

Understanding a few basic points about the anatomy of this nerve is key to making the diagnosis of ulnar neuropathy, or one of its mimics. The ulnar nerve is derived from the spinal nerve roots C8 and T1. These fibres pass through the lower trunk and medial cord of the brachial plexus. The ulnar nerve itself arises from the plexus in the proximal axilla, then lies on the medial aspect of the upper arm (fig 1). The anatomy of the nerve at the elbow is particularly important. Here the nerve lies in the bony ulnar (condylar or retroepicondylar) groove behind the medial epicondyle of the distal humerus (fig 2). As it emerges from this groove, it passes under the aponeurotic arch of the flexor carpi ulnaris muscle (also called the humeroulnar arcade). This is formed from the attachment of the muscle to the medial epicondyle and the olecranon (fig 2). Its edge usually lies about 1 cm distal to a line joining those two points.

Figure 1

Anterior aspect of the right arm, showing the course and important branches of the ulnar nerve. At the wrist the ulnar nerve passes through a fibro-osseous space called Guyon’s canal. The nerve divides …

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