Keywords; inter scalene triangle, thoracic outlet.
Five large trunks of nerves known as the brachial plexus emerge from
the lower neck; together with the large subclavian artery that supplies
the arm with blood, they pass from the chest cavity via this
narrow passageway to the upper limb.
Inter because it lies between two small muscles in the neck called the anterior and medial scalenes; and the word triangle is used because it is bounded beneath on the third side by the first rib.
Clinically, this space is of vital importance being the underlying cause of many of the debilitating upper limb syndromes.
Vital structures pass through this passage on their way to the limb. In a small percentage of cases the subclavian vein passes through the space bringing venous blood back from the arm. Then swelling is a possibility; a clot is not common, but must be first differentially diagnosed, obviously.
Spasm of the scalene muscles, a subluxated first rib or a cervical rib are often at the root of conditions like carpal tunnel syndrome; tingling in the fingers always excludes the pinkie.
A thoracic outlet syndrome, as it is known, very frequently does affect the pinkie as the lowermost trunk of the brachial plexus lies directly on the first rib.
Remember, the classic carpal tunnel syndrome where the median nerve is pinched in the wrist, never affects the pinkie.
Through this triangle pass the artery and nerves to the arms.
The anterior border of this triangle is the anterior scalene muscle which laterally flexes the neck to the same side, and raises the first rib.
It originates from the transverse processes of the middle cervical vertebrae and inserts into the first rib.
The nerve supply is from the C4 to C6 spinal nerves.
The posterior border of the triangle is the medial scalene muscle. It too originates from the transverse processes of the cervical vertebrae and inserts further posteriorally on the first rib; behind the subclavian groove in the rib for the artery.
It too laterally flexes the neck and raises the first rib.
The nerve supply is the cervical spine nerves, C3 to C6.
Incidently, if you have swelling in the lower arm it's not likely to be a classic case of thoracic outlet syndrome.
The venous blood return from the arm is via the subclavian vein which does not pass usually through the inter scalene triangle. Can you spot the groove in the first rib where it usually goes?
In my book, if your lower arm is swollen, think first of seeing your medical doctor, not your chiropractor. True, it could be a strain or sprain in the lower arm, but first we should rule out a clot in the vein, or more serious, a mass, from the lung, for example, pressing on the vein.
There are many conditions that can affect the scalene muscles including an interference of one of the cervical spine nerves, C3 to C6. Subluxations of the mid to lower vertebrae are common, caused by
A careful, thorough examination is called for obviously when faced with the patient suffering from neck pain, with or without swelling and tingling in the arms and hands.
In chiropractic nomenclature this is described as the vertebral subluxation complex; you'll find the link lower down.
Again notice how the subclavian vein does not usually pass through the inter scalene triangle, but it does pass throught the thoracic outlet and under the clavicle. Sub-clavian meaning under the clavicle.
In the normal spine only the twelve thoracic
vertebrae have ribs however anomalies do occur. Fairly commonly the
first lumbar vertebra may have a small rudimentary rib, mostly usually
associated with another anomaly at the lumbosacral junction; see the sacralization of L5 casefile page.
Less commonly, the last cervical vertebra, C7, may also have a rudimentary rib. Mostly they are quite small and of no clinical significance. But very occasionally the cervical rib may be quite large and, because it also passes through this narrow space, taking up room, it may impinge on either the subclavian artery or the brachial plexus producing a bizarre mixture of vascular and neurological signs in the arm.
Here is a simple test that you can do. Raise your arm above your head as you would do, say, as in hanging the washing. Does it increase the tingling in your arm or does it relieve it?
The whole is complicated by the close approximation of the collar bone; these structures, after leaving the inter scalene triangle must pass through the so called thoracic outlet. Raising the arms closes down this space; if the impingement is in this region then you will get increased symptoms.
It's well recognised that casefiles have no scientific status, but they do give us insight into how others perceive their problems, and howthey cope, or don't cope. And whether chiropractic has a contribution to make or not. Do keep in mind that very large cervical ribs like this one are relatively rare. Not every tingle in the arm is caused by a cervical rib!
Do you have a question? Shoot! Please include important details such as when the problem started, what increases and relieves the pain, which movements cause dizziness, whether the pain radiates to all the fingers or just the thumb and forefinger, for example.
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