Anatomical work-up of an individual with multiple muscular variants on both forearms

AbstractMuscular variants of the forearm are common and frequently cause neurovascular compression syndromes, especially when interfering with the compact topography of the carpal tunnel or the Canalis ulnaris. Here, we report on a male body donor with multiple muscular normal variations on both forearms. The two main findings are (1) an accessory variant muscle (AVM) on the right forearm originating from theM. brachioradialis, the distal radius, and theM. flexor pollicis longus. It spanned the wrist beneath theFascia antebrachia and inserted at the proximal phalanx of thedigitus minimus. (2) Moreover, we found a three-headed palmaris longus variant on the left arm with proximal origin tendon and a distal, trifurcated muscle belly, with separated insertions at the palmar aponeurosis, the flexor retinaculum, and, in analogy to the accessory muscle on the contralateral arm, at the base of the proximal phalanx of thedigitus minimus. We found a considerable thickening of the left-hand median nerve right before entering the carpal tunnel indicative of a possible chronic compression syndrome adding clinical relevance to this anatomical case. We also discuss the notion that both, the AVM and the contralateral three-headed palmaris variant are developmental descendants of theM. palmaris longus. Additionally, we found a previously not recorded variant of theM. palmaris brevis on the left hand.

Source: Anatomical Science International - June 16, 2021 Category: Anatomy Source Type: research