Presentation
Hypoesthesia of the 4th and 5th digits at the palmar/ulnar aspect. Mildly painful and slightly weakened flexion of the wrist and fingers. Tinel sign positive over ulnar sulcus at the elbow. ENG test is suggestive of focal sensory-motor neuropathy of the ulnar nerve at the level of the ulnar sulcus.
Patient Data
MRI shows a small muscle at the ulnar sulcus, just ulnar and distally of the triceps femoris long head insertion, and proximally of the flexor carpi ulnaris origin (arrows), contributing to the roof of the cubital tunnel superficially to the ulnar nerve. The ulnar nerve is being slightly compressed at this level and is conspicuously enlarged just distally of this finding.
Case Discussion
The anconeus epitrochlearis muscle is an accessory muscle at the elbow, situated between the ulnar aspect of the olecranon and the posterior aspect of the medial humeral epicondyle. It is a variant of the anconeus muscle, which is situated at the same level but at the posterior radial aspect of the elbow, between the proximal ulna and the lateral humeral epicondyle.
The anconeus epitrochlearis muscle is usually asymptomatic, however, sometimes it can compress the ulnar nerve leading to peripheral neuropathy. In this case, there was a strong clinical suspicion of cubital ulnar nerve compression, which the MRI corroborated.
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