Thoracic Outlet Syndrome
Thoracic Outlet Syndrome (TOS) is characterized by upper extremity pain or paresthesia caused by occlusion, compression, injury or irritation to the neurovascular structures traversing the thoracic outlet.
Thoracic outlet syndrome is generally a benign mechanical disorder but two potentially threatening vascular origins should be excluded.
- Arterial TOS is caused by occlusion of the subclavian artery from stenosis, aneurysm, embolus, or compression from a cervical rib or anomalous first rib. It is the most serious cause of TOS but accounts for less than 1% of all cases. Arterial TOS results in coldness, weakness, fatigability and diffuse pain.
- Venous TOS is caused by subclavian vein obstruction and results in symptoms of claudication: edema, cyanosis, and venous dilation. Venous TOS is the causative mechanism for less than 5% of all cases of TOS. A variant form of venous TOS called Paget-Schroetter syndrome results in “effort thrombosis” where claudication symptoms are precipitated by strenuous activities involving arm abduction.
- The remainder of TOS patients suffer from benign mechanical compression of the neurovascular bundle or “Neurogenic TOS”. Neurogenic thoracic outlet syndrome is by far the most common cause of TOS, accounting for well over 95% of all cases. Neurogenic TOS results from compression or irritation to the lower trunk or medial cord of the brachial plexus. Neurogenic TOS (hereinafter referred to as simply TOS) is subdivided into one of three primary sites of compression. “Scalene” induced TOS occurs from the compression of the neurovascular bundle between the anterior and middle scalene muscles. “Pectoral” compression occurs beneath the pectoralis minor tendon. “Costoclavicular” compression happens between the first rib and clavicle.
Thoracic Outlet Syndrome Causes
Anatomical predisposing factors for costoclavicular TOS include tightening or thickening of the fascial band that connects the first rib to the clavicle, and the presence of a cervical rib. Cervical ribs are present in approximately 1% of the population and are bilateral in 80% of cases. Although cervical ribs can be a causative factor for costoclavicular TOS, less than 10% of patients with cervical ribs will experience TOS complaints. Additional contributing factors include osseous overgrowth of a prior clavicle or first rib fracture and a history of trauma. Up to 23% of cervical soft tissue injuries may include a TOS component.
Poor posture, especially upper crossed syndrome, is a predisposing factor for all mechanical forms of TOS. Static postures such as those required by computer users, assembly line workers, supermarket checkers, and students, predispose to TOS, as do occupations requiring prolonged overhead activity i.e. electricians and painters. Swimmers, volleyball players, tennis players, and baseball pitchers are subject to predisposing stressors.
Most patients presenting with TOS are between the ages of 20-60, with a peak incidence in the fourth decade. TOS is more common in women with some estimates as high as 9:1. The shape of the chest, including traction from pendulous breasts, is thought to promote “shoulder drooping” and ongoing downward pressure on the shoulder which further close the thoracic outlet.
Thoracic Outlet Syndrome Symptoms
Symptoms of TOS include pain, paresthesias, and motor weakness. Neck, arm and hand pain is often insidious in onset and aggravated by elevation of the arms or excessive head and neck movement. A thorough neurological evaluation will help establish the diagnosis and rule out other conditions. Pain and paraesthesia predominately involve the C8/T1 segmental level. Symptoms follow an ulnar nerve distribution in 90% of cases. Motor deficits, especially diminished grip strength, are possible, but reflex changes are suggestive of more central pathology.
Treatments (thoracic outlet syndrome and chiropractic)
In the absence of acute or threatening neurovascular problems, conservative care should be the treatment of choice for TOS. The treatment pathway for TOS is based upon the specific site(s) of neurovascular compression, but clinicians should keep in mind that TOS is often multifactorial in origin and successful management needs to address each component.
Joint manipulation may be indicated for restrictions in the cervical spine, first rib, cervicothoracic junction, shoulder, elbow, hand, and wrist. Stretching and myofascial release techniques should address problems in the cervical spine, scalenes and pectoral muscles as well as distal sites of potential “double crush” involvement, i.e. cubital tunnel, carpal tunnel, wrist flexors, etc. Retraining of postural faults and diaphragmatic breathing is critical. Nerve mobilization, particularly for the ulnar nerve, will likely play a role in recovery.
Lifestyle modifications may include:
- Avoidance of repetitive postural stress and workstation modification.
- Patients should avoid carrying heavy loads, especially on their shoulder i.e. carpet rolls.
- Briefcases, laptop cases or heavy shoulder bags should be lightened. Bra straps may need additional padding or consideration of replacement with a sports bra.
Surgical treatment of TOS remains controversial. Even in the presence of a symptomatic cervical rib, studies have shown that candidates who undergo surgical resection do not have functional improvements matching those who choose conservative care.