Anatomy and Pathophysiology of NTOS

Neurogenic TOS is usually due to a combination of predisposing factors and a hyperextension neck injury. Predisposing factors include cervical rib variants and anomalous first ribs, a narrow scalene triangle, and various congenital bands and ligaments. The most common trauma is a whiplash injury, usually from a motor vehicle accident. The pathophysiology is felt to begin with trauma to the scalene muscles causing tearing of muscle fibers and hemorrhage with subsequent replacement of the blood with microscopic scar tissue throughout the scalene muscles. The now-tight muscles compress the nerve roots and trunks of the brachial plexus, subsequently causing the classic symptoms of extremity pain, paresthesias, and weakness. Further, the injured scalene muscles lead to neck pain and occipital headaches which are referred from the transverse process muscle origin.