Variant Distal Ulnar Nerve Loop: A Previously Undescribed Anatomical Finding.

Cureus. 2018 May 10;10(5):e2604. doi: 10.7759/cureus.2604.

Patel M, Iwanaga J, Oskouian RJ, Tubbs RS.

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Abstract

A previously undescribed variant ulnar nerve loop was discovered during the routine anatomic forearm and hand dissection of an adult female. The major finding was that of a large loop traveling around the distal tendon of the flexor carpi ulnaris. The variation presented here appears to be unique. The exact function of such derailed anatomy is not clear but, if found during surgery, might confound normal dissection methods or, when present, could result in varied clinical presentations regarding the sensory or motor examination of the hand.

KEYWORDS:

anatomy; anomalies; cadaveric; hand surgery; loop; ulnar nerve; variations

Figure 1

Left Anterior Forearm and Hand Dissection

Figure ​Figure1A:1A: Left palmar surface of the left hand and distal anterior forearm displaying the ulnar nerve in its anatomical position (arrowheads).

Figure ​Figure1B:1B: Figure ​Figure1A1A with the ulnar nerve main trunk rotated 180 degrees and then retracted medially. Note the variant loop formed around the flexor carpi ulnaris. White arrowheads: ulnar nerve main trunk; Black arrowheads: variant loop around the distal tendon of the flexor carpi ulnaris; White arrow: deep branch of the ulnar nerve; Superficial branch of the ulnar nerve retracted at right forceps; Red arrow: additional nervous interconnection; Green arrow: Riché-Cannieu anastomosis between the superficial ulnar nerve branch and median nerve in the hand.