The thoracic outlet is a space in the body that sits between the lower part of the neck and the collar bone. The thoracic outlet contains a bundle of blood vessels and nerves that supply the arm and stretches to the upper half of the arm. Thoracic Outlet Syndrome, later referred to as TOS, describes a series of conditions that cause compression of the major nerves and/or blood vessels that run through that thoracic outlet space.
There are three different types of thoracic outlet syndrome, and all of these are named after the type of vessel being compressed.
The most common type of TOS is neurogenic TOS, which occurs when the brachial plexus is compressed. The neurogenic kind accounts for almost 90% of all TOS cases. Neurogenic TOS is characterised by a later onset of symptoms, such as diminished feeling along the arm and possibly hand muscular weakness.
Venous TOS is caused when the axillary or subclavian vein is being compressed in the thoracic outlet. Symptoms of venous TOS would be more abrupt in onset and includes venous distention in the neck and pain ranging from the arm to the forearm.
Arterial TOS is caused when the axillary or subclavian artery is being compressed in the thoracic outlet. Like the venous type, arterial TOS will also present with a more abrupt onset of symptoms, including color changes in the fingers and diminished pulses.