TOS is unlikely to be due to a single underlying cause. The manifestation of TOS is due a combination of factors, some of which are more obvious than others (e.g. an abnormal rib). It is therefore likely to be an interplay between predisposing anatomy, precipitating (or triggering) event and/or perpetuating factors.


Predisposing anatomy:

There is a wide spectrum in normal human anatomy and any variation that results in reducing the available space for the nerves, artery or vein can potentially predispose to compression or stretching of these structures. Historically, the presence of an additional rib (the “cervical rib”) was an obvious anatomical variation. It is now recognised that variations in the first rib, muscles and ligaments/ tendons are more common causes. As for example, an excessively conical rib cage with a very oblique lying first rib can stretch the nerves excessively especially if the scalenius muscle is also bulky. Not surprisingly, these anatomical changes reach maturity after adolescence, and this is often the time when symptoms begin to manifest.


Precipitating/ Triggering event:

Trauma is often cited when patients first experience symptoms. This used to be ascribed to whiplash although falls, recreational, sport and occupational injuries plays an increasing role now. Sometimes, it is due to minor, repetitive trauma (microtrauma) that causes long term damage, often unknown to the patient.


Perpetuating factors:

Poor posture, movement system disorders and habitual activities all contribute to aggravate the condition. Sometimes, these are a result of the patient’s protective  response but may in fact worsen the condition, e.g. muscle spasm becomes worse as the muscles shorten in response to pain.

Contacting Us


The Small Print

Mr Colin Chan
Consultant Vascular Surgeon
Wirral University Teaching Hospital
Wirral CH49 5PE

Mrs Louise Rule
Wirral University Teaching Hospital
Wirral CH49 5PE

(+44 151 604 7530)


Spire Wirral Hospital
Holmwood Drive
Wirral CH61 1AU

(+44 151 929 5181)

Spire Manchester Hospital
170 Barlow Moor Road
Manchester M20 2AF

(+44 161 447 6600)