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Thoracic Outlet Syndrome

Exploring the Complexities of Nerves in the Thoracic Outlet


Thoracic Outlet Syndrome (TOS) refers to a group of three related conditions, where the nerves, and/or blood vessels passing through the thoracic outlet, are compressed leading to pain in the arm, shoulder, and neck.

The thoracic outlet is an area located just above the armpit and near the base of the neck and multiple blood vessels and nerves are contained within this confined area. Thoracic outlet syndrome can occur primarily in three main “compartments” or zones within this space:

Interscalene Triangle: Near the neck.

Costoclavicular Space: Between the collarbone and first rib, or

Subcoracoid Space: Below the shoulder (1)

    What are the types of TOS?

    •   Neurogenic TOS

    Neurogenic TOS is the most common form and is observed in almost 90% of all cases and arises when the nerves that connect the neck to the arm (the brachial plexus) becomes compressed.

    •   Venous TOS

    Venous TOS occurs in almost 5% of the population and is observed when the veins in the thoracic region is compressed and damaged, leading to upper body thrombosis (Blood clots).

    •   Arterial TOS

    Arterial TOS occurs in only 1% of the population and is observed when the arteries passing through the thoracic region becomes compressed, resulting in a bulge, known as an aneurysm (2)


    Thoracic Foraminal Narrowing:

    • Balance issues
    • Upper back pain
    • Numbness or tingling and pain around or below the abdomen
    • Radiating pain around the ribcage or even into the abdomen

    Lumbar foraminal Narrowing:

    • Low Back Pain than may come and go
    • Numbness or tingling in the lower extremities
    • Reduced strength in the legs and feet
    • Radiating pain down the buttocks in to the feet
    • Loss of bladder control
    • Pain that improves with sitting, leaning forward, or bending forward (3, 4)

    What causes Neural Foraminal Narrowing?

    The majority of neural foraminal Narrowing causes are degenerative, meaning they develop gradually with age. It may also result from physical trauma or accidents. Other causes include:

    • Osteoarthritis: Bone spurs can form as a result of cartilage breakdown in the facet joints, intruding into the neural foramina.
    • Disc Degeneration: The intervertebral discs may become herniated, further narrowing the space in the neural region.
    • Paget’s disease: Which can cause an overgrowth in the vertebral bone, leading the tightening of the neural space.
    • Ligamentum Flavum Hypertrophy: The ligaments may become enlarged which can bulge into your foramen
    • Spondylolisthesis: One vertebra slipping over another can reduce the size of the neural foramen
    • Facet Joint Subluxation: Misalignment of the facet joints can result in foraminal narrowing

    Besides these, congenital causes such as Congenital Stenosis, where individuals are naturally born with a narrow foramen can also lead to Neural Foraminal Narrowing. Moreover, Accidents or traumatic injury into the spinal column or the surrounding muscles and ligaments can result in this condition (5, 6).

    What are the Symptoms of TOS?

    Neurogenic TOS

    Symptoms of neurogenic thoracic outlet syndrome include:

    • Ache in the arm, shoulder, and neck
    • Feeling numb and tingly, especially in the fingers
    • Arm weakness or fatigue
    • A weakening grip
    • A dull pain in the hand or arm
    • Reduced capacity for fine motor tasks, such as writing by hand or buttoning clothes

    Venous TOS

    Symptoms of venous thoracic outlet syndrome can include:

    • Swelling of the arm or hand
    • Hand discoloration, generally bluish, of one or more fingers.
    • Arm ache and fatigue
    • More noticeable veins on the skin

      Arterial TOS

      Among the symptoms of arterial thoracic outlet syndrome are:

      • Coldness in the hand or arm
      • Pallor (pale skin color)
      • Exertion-induced arm or hand pain
      • Muscle atrophy in severe situations
      • Weak or absent pulse in the affected arm
      •  A throbbing lump around the collarbone
      • Cold fingers, hands, or arms (3)

      What causes TOS?

      The etiology of Thoracic Outlet Syndrome (TOS) is multifactorial and can encompass anatomical abnormalities, postural imbalances, and trauma.

      Neurogenic TOS

      • Additional rib: some people are born with an additional rib near the collarbone, which can cause nerve compression.
      • Tight muscles: the muscles in your neck and shoulders might become tight or swollen, pressing against the nerves.
      • Poor posture: slouching or keeping your head too far forward might put pressure on your nerves.
      • Repetitive movements: occupational or recreational repetition of the same arm or hand movements might cause nerve pressure.
      • Heavy carrying: Carrying heavy bags or objects can put strain on your neck and shoulder muscles, causing nerve squeezing.

      Arterial and Venous TOS

      • Additional Rib or Abnormal Bone Structure: An additional rib, can also can press against blood arteries.
      • Any type of trauma or scarring at the collarbone might disrupt blood flow.
      • Repetitive Use or Heavy Lifting due to one’s occupation or recreational activities
      • Pregnancy: Changes in the body during pregnancy can sometimes induce transient symptoms of TOS (4, 5)

      How is TOS diagnosed?

      Since many conditions have symptoms with TOS, diagnosing it can be challenging. These conditions with similar symptoms include:

      • Fibromyalgia
      • Cervical disc disorders
      • Rotator cuff injuries
      • Multiple sclerosis
      • Complex regional pain syndrome
      • Tumors of the syrinx or spinal cord etc.,

      In certain cases, a physical examination can diagnose TOS by testing the:

      • Tenderness in the region extending toward the cavity of the neck from just above the clavicle or collarbone.
      • Sensation of weakness or “pins and needles” when the palms are raised.
      • Paleness in the palms of one or both hands

      Besides physical examination, a physician can also conduct some provocative tests to test nerve and blood vessel performance in the thoracic region. Some of these tests are:

      • Adson’s Maneuver

      A deep breath is taken and held while the neck is stretched out and the head is turned toward the side that aches. If the pulse in the wrist goes away or gets weaker, that means the test is positive.

      • Wright’s Test

      While taking deep breathes, the arm is raised to the side. If the wrist pulse goes away or gets weaker, it means the test was positive.

      • Roos Stress Test

      For up to three minutes, the arms are raised and the hands are opened and closed. Feeling numb, tingly, or weak during the test is considered positive for TOC.

      Furthermore, in order to diagnose TOS, the physician may perform supplementary imaging studies and specialized tests. They are:

      • X-ray:
      • MRI (Magnetic Resonance Imaging):
      • CT Scan
      • Ultrasound
      • Electromyography (EMG) and Nerve Conduction Studies
      • Electromyography (EMG) and Nerve Conduction Studies
      • Angiography
      • Venography (6, 7)


      How is TOS treated?

      Thoracic Outlet Syndrome (TOS) is usually treated with a combination of different types of medicine that are based on the type of TOS and its underlying reasons.

      Non-Surgical Interventions

      Physical Therapy: Exercises aim to improve posture and strengthen the muscles around the neck and shoulders, which can alleviate symptoms.

        Medication: Anti-inflammatory medications and muscle relaxants may be prescribed to reduce pain and inflammation.

        Lifestyle Modifications: Patients are often advised to avoid activities that exacerbate symptoms and to practice ergonomic strategies in daily tasks.

        Pain Management: Options may include nerve blocks or injections to alleviate pain temporarily.

        Surgical Interventions

        Scalene Anterior Muscle Resection: Involves the removal of a portion of the scalene muscle to relieve nerve compression.

        First Rib Resection: Removing the first rib can create more space for the neurovascular bundle.

        Clavicle Resection: Rarely performed, but involves removing a section of the clavicle or collarbone to relieve vascular compression.

        Arterial and Venous Procedures: For vascular TOS, arterial repair or venous angioplasty may be considered.

        Thoracoscopic Surgery: A minimally invasive approach for selected cases (8).


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        1. Huang JH, Zager EL. Thoracic outlet syndrome. Neurosurgery. 2004;55(4):897-903.
        2. Kuhn JE, Lebus GF, Bible JE. Thoracic outlet syndrome. JAAOS-Journal of the American Academy of Orthopaedic Surgeons. 2015;23(4):222-32.
        3. Brantigan CO, Roos DB. Diagnosing thoracic outlet syndrome. Hand clinics. 2004;20(1):27-36.
        4. Sessions R. Recurrent thoracic outlet syndrome: causes and treatment. Southern Medical Journal. 1982;75(12):1453-61.
        5. Sheth RN, Belzberg AJ. Diagnosis and treatment of thoracic outlet syndrome. Neurosurgery Clinics of North America. 2001;12(2):295-309.
        6. Sanders RJ, Hammond SL, Rao NM. Diagnosis of thoracic outlet syndrome. Journal of vascular surgery. 2007;46(3):601-4.
        7. Sanders RJ, Pearce WH. The treatment of thoracic outlet syndrome: a comparison of different operations. Journal of vascular surgery. 1989;10(6):626-34.
        8. Povlsen B, Hansson T, Povlsen SD. Treatment for thoracic outlet syndrome. Cochrane Database of Systematic Reviews. 2014(11).