Lipomatosis of dorsal cutaneous branch of ulnar nerve – a rare cause of sensory neuropathy of dorsum of the hand

Abstract

Wrist pain along the ulnar aspect is a diagnostic dilemma for a long time, this is because of the complex anatomy and numerous pathologies related to these structures. The most common cause is the tear of the triangular fibrocartilage complex. The remaining etiologies are lunotriquetral ligament tears, extensor carpi ulnaris tendon disorders, distal radioulnar joint disorders, impingement and impaction syndromes, pisotriquetral joint disorders, and ulnar wrist masses. Imaging is an important cornerstone in the evaluation of ulnar-sided wrist pain which aids the clinical history and physical examination. X-rays, USG, CT, magnetic resonance imaging (MRI), and MR arthrography are the currently available modalities that are often used to guide diagnosis and treatment. However, while requesting MRI, the need for inclusion of distal forearm is not well understood. In this case report, we describe a rare cause for ulnar-sided wrist pain which was diagnosed accurately with MRI. The inherent properties of MRI and the inclusion of the distal forearm helped us in reaching the final diagnosis. With this case report, we describe the ability of MRI to detect the nature of the lesion which helped to preclude the need for biopsy, hence entitling it as a “do-not touch lesion.”