Extensor digitorum brevis manus is uncommon but can easily be misinterpreted during wrist ultrasound examination

In our case, concomitant presence of the EDBM muscle and the ganglion cyst further congested the compartment. [...]after repetitive wrist movements, the blood flow to the EDBM muscle increased, resulting in a distension feeling due to muscle edema. Importantly, the synchronized movement with adjacent finger extensor tendons (on dynamic imaging) and bilateral presence (on comparative imaging) further confirmed the mass/structure to be an accessory muscle. [...]this report highlighted a relatively rare muscle variation on the dorsal hand, which should not be misinterpreted as a pathological finding during (a convenient but comprehensive) wrist US examination.