Decoding Thoracic Outlet Syndrome (TOS): Diagnosis and Treatment by Type

Thoracic outlet syndrome (TOS) produces neurologic or vascular symptoms in the upper limb, mainly because the neurovascular bundle (the brachial plexus and subclavian vessels) is compressed by bony and/or muscular structures above the first rib and behind the clavicle. The symptoms vary widely depending on which structure is compressed or irritated.

People with TOS may have a double crush pattern (compression at both the cervical spine and a distal peripheral nerve), which may mean the incidence of TOS is underestimated. Among the TOS patients studied, besides those with bilateral carpal tunnel syndrome (CTS), there were also patients with unilateral CTS and patients with cubital tunnel syndrome of the ulnar nerve.

Epidemiology

• 1 to 2% of the population

• Women more than men (3:1), but in athletic populations it is more common in men than women

• Tends to affect tall, slender people with a long neck and drooping shoulders

• More common between ages 20 and 60; the vascular form is most often diagnosed in patients aged 20 to 30, and the neurogenic form in patients aged 20 to 40

• Three types:

• Neurogenic: accounts for over 95% of cases; nTOS can be further divided into true nTOS (with objective findings) and disputed nTOS (lacking objective findings)

• Venous: accounts for 4% of cases

• Arterial: under 1% of cases

Etiology and pathophysiology

Anatomically, the abnormalities can be divided into soft tissue (70%) and osseous (30%).

Soft tissue

• Scalene muscle anomalies, hypertrophy of the anterior scalene

• The passage of the brachial plexus through the anterior scalene: within the interscalene triangle rather than behind it

• Variations in muscle origins and insertions: the anterior part of the middle scalene inserting on the first rib

• Scalenus minimus: an accessory muscle found in 30 to 50% of TOS patients

• Abnormal ligaments or band-like structures

• Fibromuscular bands: increase the stiffness of the thoracic outlet and reduce its elasticity

• Costoclavicular ligament: associated with Paget-Schroetter syndrome

• Soft-tissue tumors

• Pancoast tumor: a tumor at the lung apex, seen in 1 to 3% of lung cancer cases, often lacking the typical lung-cancer symptoms (cough, hemoptysis, and dyspnea)

• Neuroblastoma

• Schwannoma of the brachial plexus

• Abnormal pectoralis minor

Osseous

• Cervical rib

• Occurs in under 1% of the population, arising from the seventh cervical vertebra, in four types

• Type 1: a complete rib connecting to the first rib or the sternum

• Type 2: an incomplete rib with a free, bulbous end

• Type 3: an incomplete rib connected distally by a fibrous band

• Type 4: a short bony bar (in millimeters) extending beyond the C7 transverse process

• Prominent C7 transverse process

• Abnormal clavicle or first rib

• Acute fracture displacement

• Hypertrophic fracture callus formation

• Fracture malunion

• Injury or dislocation of the acromioclavicular (AC) or sternoclavicular (SC) joint

• Bone tumors

• Bony metastasis to the first rib: breast, prostate, kidney

• Osteochondromatosis

Long-term overuse

• Repetitive shoulder use

  • Frequent lifting above shoulder height
  • Extreme arm positions, including excessive abduction

• At-risk athletes

• Weightlifting

• Rowing

• Swimming

• Vascular

• Repetitive compression can cause vascular injury

• Aneurysm formation

• Thrombosis

• Limb ischemia

• Other associated conditions

• Paget-Schroetter syndrome

• A type of venous thoracic outlet syndrome seen in robust young athletes

• Intermittent compression of the subclavian vein in the costoclavicular space, subsequently producing deep vein thrombosis of the upper limb

• Abnormal costoclavicular ligament

• Anterior scalene hypertrophy

Risk factors

• Repetitive work
• Overhead-type athletes: swimmers, pitchers, weightlifters, volleyball and tennis players
• Poor posture
• Middle-aged women
• Congenital anomalies: cervical rib, an overly long C7 transverse process, abnormal fibromuscular bands at the thoracic outlet
• Trauma
• Obesity

History

• Neurologic and vascular symptoms are related to specific postures and are worsened by lifting heavy objects, overhead activity, and shoulder abduction and external rotation

• Neurogenic:

• Pain in the arm, shoulder, and neck

• Numbness and tingling, commonly in the ulnar nerve distribution

• Headache

• Forearm muscle cramps

• Difficulty with fine motor movements

• Sensory loss, muscle weakness, and atrophy (late findings)

• Gilliatt-Sumner hand: severe atrophy of the abductor pollicis brevis, with mild atrophy of the interossei and hypothenar muscles

• Venous

• Pain

• Swelling

• Cyanosis

• A heavy feeling in the arm or hand

• Distended veins in the arm and hand

• Arterial (often asymptomatic until an embolism occurs)

  • Ischemic pain
  • Numbness and tingling
  • Pallor
  • Reduced distal pulses
  • A pulsatile mass above the clavicle

• Patients may also present with less common symptoms such as tachycardia, dyspnea, difficulty swallowing, angina-like chest pain, occipital headache, and Raynaud-like vasomotor changes in the upper limb

Physical examination

• The affected limb may show swelling or discoloration

• Muscle atrophy, weakness, and reduced strength

• Weakening or loss of distal pulses with activity or a change in position

• A vascular bruit heard in the area above the clavicle

• Provocative tests (with variable sensitivity and specificity)

• Elevated arm stress test / Roos test: for nTOS, the arms are raised overhead, mimicking a hands-up position, then the fists are opened and closed at a moderate pace for 3 minutes. If this position reproduces pain or numbness, the test is positive

• Upper limb tension test / Elvey’s test: for nTOS, the shoulder is abducted 90 degrees with the elbow extended, the wrist fully flexed, and the head side-bent toward the affected side

• Adson test: for nTOS, aTOS, and vTOS, the neck is extended and turned toward the affected side while the shoulder is slightly abducted and extended. The radial pulse is felt while taking a deep breath. If the pulse disappears and symptoms are reproduced, the test is positive

• Hyperabduction / Wright test: for aTOS and vTOS, the affected arm is progressively hyperabducted and externally rotated. If the radial pulse disappears, the test is positive

• Allen test: the elbow is flexed to 90 degrees and the shoulder is abducted and externally rotated. The patient turns the head to the side opposite the test arm; if the radial pulse disappears, the test is positive

Differential diagnosis

• Cervical disc disease
• Rotator cuff tear / impingement syndrome
• Brachial plexus neuritis
• Carpal tunnel syndrome
• Ulnar nerve entrapment
• Complex regional pain syndrome
• Polymyalgia rheumatica
• Fibromyalgia
• Subclavian steal syndrome
• Vasculitis
• Raynaud’s disease
• Multiple sclerosis
• Spinal cord tumor
• Pancoast tumor
• Neurofibroma
• Bursitis
• Osteoarthritis of the scapular/clavicular joints

Diagnostic tools

• X-ray (cervical spine and chest): to assess for a cervical rib or other thoracic pathology
• MRI: to determine the location and cause of compression, or to identify abnormal muscular fibrous bands
• Ultrasound: to document the degree of vessel narrowing, the presence of an aneurysm, or to confirm thrombosis
• Electromyography / nerve conduction studies: to understand brachial plexus compression
• Angiography / venography: when arterial or venous thoracic outlet syndrome is suspected and for surgical planning

Initial treatment

• Conservative treatment is the initial approach, unless there is thromboembolism with acute vascular occlusion, stenosis, arterial dilation, or worsening nerve injury. In studies, conservative treatment successfully relieved symptoms in about 60 to 70 percent of nTOS patients; these are study results and do not predict any individual’s outcome.

• Activity modification, weight reduction

• Medications include:

• Non-steroidal anti-inflammatory drugs (NSAIDs)

• Muscle relaxants

• Tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs)

• Physical therapy includes

• Postural retraining

• Strengthening and lifting the shoulder-girdle muscles

• Stretching/strengthening of the pectoralis minor and scalenes

• Scapulothoracic mobility

• Trigger-point treatment

• Soft-tissue work

• Botulinum toxin, corticosteroid, or local anesthetic injection:

• Can be guided into the scalene muscle by CT scan, ultrasound, or other methods

• May serve as a short-term adjunct to non-surgical treatment, used together with physical therapy, or as a bridge before surgery

• When venous thoracic outlet syndrome is present with thrombosis:

• Thrombolytic and anticoagulant therapy

Surgery

• Some studies suggest that for athletes with TOS, conservative treatment with monitoring for at least 1 month is recommended, with periodic assessment during rest to see whether symptoms improve. If symptoms improve and activity can be resumed, conservative treatment should be continued.

• If there is no benefit, worsening, or an inability to return to sport (or normal daily activities), surgery should be considered promptly to reduce the risk of long-term nerve injury and potential arterial thrombosis.

• Surgery is one option for neurogenic thoracic outlet syndrome; if an injection relieves symptoms, it suggests that first-rib resection / anterior scalenectomy may be beneficial.

• Post-surgical rehabilitation

• Focuses on controlling pain, reducing swelling, maximizing neck/shoulder range of motion, wound healing, and appropriate graded physical therapy

• In the first 3 to 4 weeks, strength training should be avoided. Passive and assisted exercises are used to increase shoulder range of motion and nerve gliding, with emphasis on improving posture and muscle condition.

• By week 8, resistance training for the muscles around the scapula is begun, aiming to maintain full range of motion and physiologic movement patterns

• If returning to competitive sport is the goal after surgery, at 12 weeks the training is handed over to a sports coach to begin a sport-specific program. A full return to high-level competition may take 9 to 12 months after surgical decompression

Prognosis

• Post-stenotic dilation of the subclavian artery leading to aneurysm formation and possible thromboembolism in the affected upper limb (arterial thoracic outlet syndrome)

• Pulmonary embolism, residual symptoms, and a high recurrence rate (venous thoracic outlet syndrome)

• Persistent motor impairment (neurogenic thoracic outlet syndrome)

References

• J Shoulder Elbow Surg. 2022 Nov;31(11):e545-e561. doi: 10.1016/j.jse.2022.06.026. Epub 2022 Aug 10.
• Healthcare (Basel). 2018 Jun 19;6(2):68. doi: 10.3390/healthcare6020068.
• Br J Sports Med. 2013 Nov;47(17):1080-4. doi: 10.1136/bjsports-2013-093002. Epub 2013 Sep 17.