Inter scalene triangle

Inter scalene triangle conditions can affect the artery and nerves passing to the arm; tingling and sometimes pain is common, increased by raising the affected limb above the head.

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.

Inter Scalene Triangle

Through this inter scalene triangle pass the artery and nerves to the arm.

Anterior Scalene muscle

The front 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.

Incidentally, 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

  • poor posture, for example long hours at the computer.
  • falling asleep in the car or plane or in front of the TV.
  • sleeping on the abdomen.
  • injuries to the neck such as whiplash, falls from a horse or whilst skiing; diving into shallow water.
  • talking for an extended period with someone sitting to the side; for example, at the dinner table.
  • holding the telephone between neck and shoulder; Pinched nerve in neck ...
  • many others.

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.

Medial Scalene muscle

The posterior border of the inter scalene 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.

Vertebral subluxation complex

In chiropractic nomenclature this is described as the vertebral subluxation complex; you'll find the link lower down.

Tingling in arms and hands

Tingling in arms and hands is probably one of the most common complaints at chiropractic help. The inter scalene triangle is quite involved in one way or another.

Most commonly the lowermost trunk is affected in the inter scalene triangle causing tingling in the pinkie and ring finger, but the whole hand may be affected.

Thoracic outlet syndrome

Entrapment of either the artery or the nerves of the brachial plexus as they pass through the inter scalene triangle is known as the thoracic outlet syndrome.

Again notice how the subclavian vein does not usually pass through the inter scalene triangle, but it does pass through 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.

Cervical ribs

Less commonly, the lowermost neck vertebra, C7, may also have rudimentary cervical ribs. Mostly they are quite small and of no clinical significance. But very occasionally it may be quite large and, because it also passes through this narrow space, the interscalene triangle, 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 how they do 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! 

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