A bifurcated anterior scalene muscle: A case report

Abstract

Anomalies of the structures related to the scalene triangle have been reported in the literature as a cause of either vascular or neurogenic thoracic outlet syndrome (TOS). This case report details a male cadaver with a right anterior scalene muscle that was split into two bellies, enclosing the right subclavian artery anteriorly and posteriorly. The trunks of the brachial plexus ran in the space between the posterior belly of the anomalous anterior scalene and the normal middle scalene muscles. The earliest report about this anomaly that could be retrieved from the literature was recorded in 1875. The clinical implication of this anomaly involves the possible risk of developing vascular or neurogenic TOS with compression of the subclavian artery between the two bellies of the anterior scalene and/or compression of the trunks of the brachial plexus between the posterior belly of anterior scalene and middle scalene muscles.