forwards m. scalenus anterior
backwards m. scalenus posterior
down 1. rib
Compressive syndromes of the roots or peripheral nerves, mentioned above, were followed by motor and sensitive disorders on the basis of only one nerve. But one more affection exists – thoracic outlet syndrome when a multiple compression of nervous structures together with an compression of arteries and venas happen. But it is necessary to stress that nowadays this diagnosis is thought to be much more rare, than it was originally thought.
Present compression of vascular and nervous structures is called up by adverse anatomical ratios. The compression happens in the triangle border of which is:
| forwards m. scalenus anterior |
| backwards m. scalenus posterior |
| down 1. rib |
In this small space nervous plexus, vena and arteria subclavia go in an intimate closeness, and so at constriction of this space a present compression of all these structures happens.
Causes of thoracic outlet syndrome are all the processes which reduce this triangle:
| hypertrophy of m. scalenus anterior |
| anomaly of cervical of vertebras |
| pathological processes of the clavicle |
| anomaly of venas - aneurysm of artery or vena of the subclavia |
| pathological processes in the 1. rib (healing of a fracture by a callus) |
| rarely also hypertrophy of m. pectoralis minor |
In the dependence on the place of compression and main etiology sometimes particular subtypes of the outlet syndrome are differed, but for clinical practice this dividing is needless.
| Syndrome | Place of compression |
|
Scalene |
between the m. scalenus anterior and the first rib (usually cervical rib) |
|
Costoclavicular |
between the first rib and the clavicle |
|
Hyperabductive |
between the m. pectoralis minor and the rib |