Arterial embolism from anatomical variation at the thoracic outlet.

Thoracic outlet syndrome (TOS) represents a constellation of symptoms arising from the compression of the neurovascular bundle as it exits the thorax. We report a unique case of multiple rare anatomical anomalies resulting in TOS manifested by distal arterial embolism. These anomalies include the combination of: (1) a unilateral right cervical rib, Gruber's type II (Gruber 1869), (2) nonunion of the first thoracic rib, (3) abnormal fibrous insertions of the anterior scalene muscle onto the epineurium of the brachial plexus and adventitia of the subclavian artery, (4) anterior position of the brachial plexus in relation to the third portion of the subclavian artery, and (5) the bifurcation of a single root of the phrenic nerve at the level of the anterior scalene muscle. This series of findings suggest an underlying developmental abnormality with a delayed onset of symptomatology consisting of the thoracic outlet syndrome.