Anatomy
Origin:
Anterior tubercles of the transverse processes of C3 to C6.
Insertion:
Scalene tubercle and upper surface of the 1st rib.
Key Relations:
-Deep to sternocleidomastoid.
-The brachial plexus and the subclavian artery pass between the anterior scalene and the middle scalene.
-The subclavian vein and phrenic nerve passes anterior to the anterior scalene as it crosses over the first rib.
Functions
-Elevates the 1st rib.
-Rotates the neck to the opposite side.
-An accessory muscle of inspiration.
Supply
Nerve Supply:
Anterior rami of C4 to C7.
Blood Supply:
Ascending cervical artery arising from the inferior thyroid artery.
Clinical
As the anterior scalene lies in close proximity to the brachial plexus, subclavian artery and subclavian vein it can give rise to compression syndromes. The patient may present with pain or paresthesia in the arm caused by nerve compression, pain, cold or pallor in the arm caused by arterial compression, or swelling in the arm caused by restricted venous drainage.
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