Thoracic Outlet Syndrome

Common symptoms of thoracic outlet syndrome

  • Numbness or tingling, “pins and needles” in the little and ring fingers, usually worse on waking up in mornings or when doing things with the elbows flexed (eg reading a book, using a tablet, working on computer)
  • Weakness or clumsiness in the hand
  • Easily dropping things or feeling tired or “cramps” in the hand
  • Difficulty with using chopsticks
  • Difficulty picking up and using small objects (eg turning a key, picking coins, buttoning up)
  • All fingers may become bent and difficult to straighten
  • Difficulty bringing the fingers together when they are extended
  • Shrinking of the hand muscles, causing more hollow spaces in the hand
  • Difficulty bringing the fingers to the thumb
  • Neck pain, shoulder pain and headaches
  • Coldness or pain in the arm and hands
  • Easily fatigued when using the hand or upper limb

2222

Wasting of the hand and thumb muscles and clawing of the fingers (right hand) in thoracic outlet syndrome

Cause of Thoracic Outlet Syndrome

2

Thoracic outlet with brachial plexus and subclavian vessels

The thoracic outlet is a narrow space between the neck and the collar bone, where all the main nerves to the upper limb (the brachial plexus) and blood vessels have to pass through on their way from the neck to the arm. This space can become narrowed by various conditions, causing increased pressure on the nerves passing through, particularly the C8 and T1 nerves that go to the small muscles of the hand and supply sensation to the little and ring fingers. All the nerves may be affected to some degree, but these two are usually the worst. Occasionally, the blood vessels may be compressed as well, resulting in intermittent disruption of the blood flow to the upper limb. This can cause intermittent coldness and pain. In severe cases blood clots can form and travel to the smaller vessels in the hand, blocking them and causing the fingers or fingertips to become gangrenous (dead and black). Pressure on the nerves prevents them from conducting electrical signals to and from the brain. This “conduction block” causes the numbness or tingling in the fingers and weakness of the muscles in the hand. The symptoms are initially mild and intermittent. Eventually, over several months to years, the numbness and tingling become more constant and the muscles in the hand start to shrink and the hand develops more sunken or hollow spaces where the muscles used to be. The hand becomes much weaker and there is difficulty doing things that require dexterity and fine finger movements such using chopsticks, keys and buttons. Because the small muscles also help to straighten the fingers and bring them together, these fingers become bent and separated. The C8 and T1 nerves also control the thumb muscles, which become weak and wasted, making it difficult to position the thumb to meet the other fingers to control small objects.

Conditions that can cause thoracic outlet syndrome include:

  • Poor neck and shoulder posture – the most common cause of neck pain and numbness
  • Abnormal extra ribs or fibrous bands in the neck crossing the nerves and blood vessels – the most common cause of blood flow obstruction
  • Fractures of the collar bone
  • Tumours or growths in the lymph nodes, lung, or nerves

2

Fibrous bands pressing on the nerves of the brachial plexus

Diagnosis of Thoracic Outlet Syndrome

If you have any of the symptoms described, see a hand specialist as soon as possible for a complete neurological and vascular examination. In addition, several investigations are usually necessary:

  • Nerve conduction and electromyography – to assess which nerves and muscles are affected and where the problem lies in the nerve
  • Neck x-rays – to look for arthritis in the neck, which can compress the nerves as they leave the spinal cord. Also to look for extra ribs.
  • MRI of the brachial plexus – to look for anything that could be compressing the nerves in the neck, including fibrous bands, extra ribs and tumours
  • Angiogram – if there are signs of blood vessel compression, an angiogram is needed to confirm the site of compression

2

Abnormal extra ribs in neck

Treatment of Thoracic Outlet Syndrome

In mild or early cases, physiotherapy to correct your posture and relax the neck muscles will decrease compression in most cases, relieving your symptoms. Physiotherapy should be done for at least 3 months.

If physiotherapy does not improve your symptoms, or when there is weakness and wasting of the muscles or signs of blood vessel obstruction, then surgery in the neck will be needed. In order to completely decompress the nerves and blood vessels in the thoracic outlet, several structures are removed. These are:

  • The scalenus muscles crossing the brachial plexus from the neck to the first rib.
  • Any fibrous bands or abnormal ribs going across or compressing the brachial plexus and subclavian vessels.
  • Any tumour causing compression
  • Part of the first rib

Following surgery, the pain and tingling sensations usually improve within a few weeks. However, if the feeling in the fingers was poor and the muscles were shrunken before the surgery, these will take several months to recover. If the condition has been present for a long time or is severe, muscle strength and sensation may not return to normal. However, the surgery prevents further deterioration of strength and feeling in the fingers.