20 - Discovery of a Novel and Bilateral Ulnar Nerve Variation: A Case Report

Poster Board Number: 20
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Odd poster #s – first hour
Even poster #s – second hour

Abstract Body : Introduction and Objective: With upper limb trauma injuries being one of the most common types of injury seen in the emergency department, it is important to take note of brachial plexus variations to ensure proper diagnosis and to account for unexplained clinical presentations. One variant that has been previously described is a communicating branch between the radial and ulnar nerve. This communication has been described in the proximal humeral region with one case report discussing a humeral shaft fracture leading to motor and sensory deficits of the ulnar nerve in addition to radial nerve deficits. The current case study discusses a novel communication between the ulnar and radial nerves found bilaterally in a female cadaver.

Materials and Methods: During a dissection elective course, two medical students completed bilateral upper limb dissections on an 84-year-old female donor in the prone position. The dissection followed a protocol adapted from Grant’s Dissector. Upon removing the skin and subcutaneous fascia on the anterior forearms, an anomalous nerve was exposed on the left and right forearm.

Results: In each forearm, the anomalous nerve was discovered arising as a branch from the radial nerve in the posterior arm, coursing around the lateral epicondyle of the humerus. The nerve then coursed obliquely from lateral to medial descending towards the distal aspect of the anterior forearm. This pattern was identical bilaterally. The accessory branch joined the ulnar nerve proper as it entered Guyon’s canal.

Conclusion and Significance: Prior studies have demonstrated the importance of appreciating ulnar nerve variants in the clinical setting when abnormal upper limb deficits arise. This case study has identified a novel communication between the ulnar and radial nerve, accentuating the relevance of ulnar nerve variants for clinicians during upper limb surgical procedures or during assessment of neuropathies and/or neural deficits of the anterior forearm and hand. Further investigation to elucidate the frequency of this variant in the general population is warranted.