A cervical rib is an extra rib that forms above the normal first rib, growing from the base of the neck just above the collarbone. The defect is present at birth, but usually not noticed until later in life.

It may be a fully-formed bony rib or just a thin strand of tissue fibres, which will not always show up on any X-ray or MRI scans you may have.

If the extra rib is only partially formed, it may either end in a swelling that shows as a lump in the neck or it may tail off into a fibrous band of tissue that connects to the first proper rib.

A cervical rib can sometimes squash one of the nearby blood vessels or nerves, causing problems such as neck pain and numbness in the arm. These symptoms are collectively known as thoracic outlet syndrome.

Thoracic outlet syndrome

Not all people with a cervical rib will develop thoracic outlet syndrome, and thoracic outlet syndrome can also be caused by other conditions.

Two major blood vessels (the subclavian artery and subclavian vein) and a bunch of nerves called the brachial plexus pass over the cervical rib. They run through a narrow space at the base of the neck towards the armpit and arm.

A cervical rib will only cause any symptoms if it is squashing these blood vessels or nerves.

Symptoms of thoracic outlet syndrome

If the extra rib does press on a vessel or nerve, you may have any of the following symptoms:

• pain in the shoulder and neck, which spreads into the arm – this may come and go or be constant
• moments where you lose feeling and have weakness or tingling in the affected arm and fingers
• moments where you can't carry out fine hand movements, such as doing up buttons
• Raynaud's phenomenon, where the blood vessels go into a temporary spasm, affecting blood supply to the fingers and toes (turning them white)
• a blood clot forming in the subclavian artery, which can affect the blood supply to the fingers, causing small patches of red or black discolouration
• swelling in the affected arm (although this is rare)

These symptoms vary widely from person to person: they may be mild or severe, be persistent or come and go.

Thoracic outlet syndrome usually starts between the ages of 20 and 50 years old, and women are more likely than men to have it.

Treatment

Most people diagnosed with a cervical rib will find their symptoms get better with time, without treatment.

Your GP may refer you to a physiotherapist for shoulder exercises designed to stretch and strengthen the neck region and correct any poor posture. The area may be massaged to release any tight or shortened neck tissues.

A referral to an occupational therapist may also be useful, for advice on techniques to protect your back and neck while at work.

To relieve any pain and inflammation, your GP may prescribe you an NSAID painkiller such as naproxen or diclofenac. Read more about non-steroidal anti-inflammatory drugs (NSAIDs).

If you develop thoracic outlet syndrome you may also be prescribed thrombolytics to break up any blood clots, and anticoagulants to prevent further clots developing.

If the above measures don't help and the symptoms persist, you may wish to consider surgical treatment to remove the extra rib, although this is often a last resort. 

Your GP can refer you to hospital, at which point your consultant will be able to explain the details of this procedure to you.