Ulnar Neuropathy as a Result of Anconeus Epitrochlearis

Abstract

After carpal tunnel syndrome, cubital tunnel syndrome is the second most common compression neuropathy in the upper extremity. Various sites of ulnar nerve compression at the elbow exist, with the most common being between the 2 heads of the flexor carpi ulnaris. Other potential sites include the arcade of Struthers, the space between Osborne's ligament and the medial ulnar collateral ligament, the medial epicondyle, the medial head of the triceps, and the medial intermuscular septum. The anconeus epitrochlearis, an anomalous muscle that runs between the medial aspect of the olecranon and the medial epicondyle, is found in up to 28% of cadavers. Although it is far less common, it must be considered when evaluating a patient with cubital tunnel syndrome. The authors report a 19-year-old man with a 2-month history of atraumatic left elbow pain accompanied by distal motor and sensory symptoms that significantly affected his activities of daily living and quality of life. After a short course of conservative management, surgical excision of the anomalous muscle, along with decompression of the ulnar nerve, was performed because of progression of symptoms. The patient had immediate improvement in subjective symptoms and strength on removal of the anconeus epitrochlearis. As shown in this case report, recovery of both motor and sensory nerve function can be achieved if the source of compression is an anomalous muscle and is treated with early surgical removal.

Anconeus Epitrochlearis Muscle Causing Ulnar Neuropathy at the Elbow: Clinical and Neurophysiological Differential Diagnosis

“…2,11 Anconeus epitrochlearis-associated ulnar neuropathy, however, usually has different characteristics than idiopathic cubital tunnel syndrome, including onset at a younger age and more rapid progress. 3,8,12 A group of patients who had anconeus epitrochlearis-associated ulnar neuropathy had a shorter duration of symptoms. 12 Some authors noted that medial elbow pain is more pronounced than sensory symptoms in these patients, and that was the case in the current patient.…”

“…2 However, the clinical diagnosis of ulnar neuropathy at the elbow as a result of this muscle variation is rare, with an unknown prevalence. 3 The anconeus epitrochlearis muscle is a congenital accessory muscle between the medial humeral epicondyle and the olecranon that covers the posterior aspect of the cubital tunnel. It is probably an atavistic structure.…”

“…1,12 In a comparative study with idiopathic ulnar neuropathy, velocity drop of the ulnar nerve was significantly associated with the presence of an anconeus epitrochlearis muscle. 3 Velocity drop was calculated by dividing the difference in velocity by distance and classified into grade + (0-2.99 m/s/cm) and grade ++ (>3.00 m/s/cm). Another study reported that ulnar nerve motor conduction studies showed conduction block, which is defined as a reduction of area/amplitude of at least 50% at a proximal site vs a distal site of stimulation, in anconeus epitrochlearis-associated ulnar neuropathy.…”

Clinical Application of Anomalous Muscles for Tendon Transfer in the Upper Limb: A Systematic Review of the Literature

“…Most of the studies were either about anatomical findings in cadavers or those found incidentally in the operating field [2][3][4][5][6][7][8][9][10][11]. Although the majority of anomalous muscles are asymptomatic, they may occasionally produce persistent pain, unexplained mass, or compression neuropathy necessitating surgical excision [7,8,[11][12][13][14][15][16][17]. Despite several anatomical descriptions, the actual reports of the clinical application of such anomalous muscles are sparse.…”

Ulnar Nerve Neuropathy Secondary to “Snapping Triceps Syndrome”

“…1,2 There are also rare reports of unusual findings including ulnar nerve compression secondary to anatomic variations in the triceps musculature. [5][6][7][8][9][10] We present a case of ulnar nerve compression neuropathy at the elbow secondary to an abnormal snapping medial head of the triceps.…”