ABSTRACT
The normal anatomy of the thoracic outlet includes three spaces through which the neurovascular structures pass. These three spaces consist of the scalene triangle, the costoclavicular space and the pectoralis minor space. Starting proximally, the scalene triangle is bordered by the anterior scalene muscle, the middle scalene muscle and the first rib. The subclavian artery and brachial plexus course through this space. The subclavian vein is anterior to the anterior scalene muscle and instead courses through the costoclavicular space, which is bordered by the anterior scalene muscle, the subclavius muscle and the first rib. The neurovascular structures then pass under the clavicle and continue laterally until the brachial plexus, axillary artery and axillary vein pass through the pectoralis minor space, which is bordered
by the pectoralis minor anteriorly and the ribs posteriorly (Figure 42.1).
