Bilateral extensor digitorum brevis manus.

Dorsal wrist pain and swelling is commonly attributed to a dorsal wrist ganglion. However, based on the authors' experience, a cautious surgeon should keep the uncommonly symptomatic diagnosis of an extensor digitorum brevis manus in their differential despite classic ganglion presentation and suggestive advanced imaging. This article describes a case of a young patient who presented with bilateral symptomatic extensor digitorum brevis manus anomalies that required surgical intervention. An extensor digitorum brevis manus is present in 3% of the population in a classic anatomy study from Japan and is most commonly symptomatic with heavy activity and extremes of wrist extension. Anatomically, the extensor digitorum brevis manus is located in the fourth wrist compartment and most commonly inserts on the index finger extensor mechanism. Examination often reveals a spindle-shaped mass that is palpable distal to the extensor mechanism and moves with extensor tendon motion. Magnetic resonance imaging shows a typical dorsal mass distal to the common extensors with a similar signal as muscle with all image sequencing. Treatment includes activity alterations to relieve symptoms or surgical excision of the muscle belly for refractory cases with care taken to preserve the index extensor mechanism.