Nonspecific functional thoracic outlet syndrome (TOS) is a common syndrome that complicates working with the arm elevated. The arm typically gets tired and numb in this position.
The diagnosis is based on patient history, clinical examination and exclusion of other disorders.
Conservative treatment is in most cases sufficient to restore function.
Definition
Thoracic outlet syndrome (TOS) comprises various types of compression of the brachial plexus and/or subclavian artery and vein in the area of the superior thoracic aperture.
TOS is most often a functional problem but is sometimes due to true impingement of a nerve or blood vessels.
Symptoms
Patients normally have problems, lack of strength, in particular, when working or performing activities with arm elevated.
If elevation of the arm causes compression of nerve structures, the symptoms include numbness of the arm, tingling, lack of strength and aching pain. The nerve compression usually affects the lower brachial plexus, meaning that symptoms occur on the C7-Th1 levels.
The pain may feel in the anterior neck, armpit, chest area, neck and shoulder region, interscapular area or even the head.
Symptoms originating from compression of the subclavian artery include limb pain, lack of strength, coolness, sensitivity to cold and muscle fatigue.
Venous TOS is associated with swelling of the limb that becomes worse in elevated position, cyanosis, aching pain and fatigue of the limb.
Diagnosis
Clinical examination is focused on the neck, shoulder and upper limb, following the normal clinical examination principles.
There are no generally approved diagnostic criteria for nonspecific TOS. Instead, the diagnosis is made by excluding other concurrent alternative aetiologies (see differential diagnosis) on the basis of symptoms and clinical findings.
Attempts can be made to provoke the symptom concerned by TOS tests narrowing the superior thoracic aperture, which are often also positive in asymptomatic patients.
In Roos' test, the patient is asked to elevate their upper arms in 90° abduction and extreme outward rotation with the elbows 90° flexed. In this position, the patient is asked to open and close their fists for 1 minute. The test is positive if there is pain or paraesthesia in the arm, making the arm drop or the test end. The examiner should also record any pallor or cyanosis in the arms.
Other provocation tests and tests measuring weakening of the radial pulse also exist.
Examinations in primary care
Plain x-ray of the cervical spine and the clavicle (skeletal anomalies)
Chest x-ray (apex of the lung)
Basic blood count with platelet count
Sedimentation rate
Need for further examinations is assessed in specialized care.
Vascular Doppler echocardiography and contrast-enhanced CT scan or MRI (when suspecting arterial or venous TOS)
ENMG (when suspecting true neurogenic TOS)
Differential diagnosis
Severe disease or in association with systemic disease (infections, brachial plexus neuritis, neoplastic or inflammatory disease, referred pain from the thoracic or abdominal cavity)
Irritiation or entrapment of a periferal nerve (carpal tunnel syndrome or cubital tunnel syndrome)
Epicondylitis
Cervical nerve root irritation
Myelopathy
Disease of the rotator cuff or shoulder joint
Dystonia
Myofascial pain
Treatment
Treatment of nonspecific functional TOS is primarily conservative. Treatment should be based on guidance for self-management.
Changing work tasks that increase symptoms into ones that cause less strain on the superior thoracic aperture (ergonomic changes) and, if necessary, analgesic medication.
Physical exercise training guided by a physiotherapist aims to improve the posture and to optimize the muscle balance in the scapular area and the superior thoracic aperture. In severe cases refractory to treatment, a multiprofessional approach should be used.
Some TOS patients with severe symptoms not responding to conservative treatment may benefit from surgery (scalenectomy or partial excision of the first rib) but there are no reliable research data available on differences in the efficacy of surgery and conservative treatment.
Surgery is considered only if there are distinct neurological symptoms or signs of ischaemia.
References
Li N, Dierks G, Vervaeke HE ym. Thoracic Outlet Syndrome: A Narrative Review. J Clin Med 2021;10(5):.[PubMed]