Middle Scalene

Original Editor - Wendy Walker

Lead Editors - Wendy Walker, Kim Jackson, Milijana Delevic, Admin, WikiSysop, Wendy Snyders, Evan Thomas and Dinalize Purcell

Description

Middle scalene or scalenus medius (Latin: musculus scalenus medius), is the largest and longest muscle in the scalene group of lateral neck muscles.^[1] Often penetrated by the dorsal scapular^[1] and long thoracic nerves^[2], it is deeply placed, lying behind sternocleidomastoid^[2].

Origin

It originates from the transverse process' posterior tubercles of C2 to C7.^[2]^[3]. Origin deviations can include the transverse process of the atlas ^[2]^[1]^[4].

Insertion

The tendon inserts onto the superior border of the 1st rib, anterior to the 1st rib's tubercle and posterior to the subclavian groove.^[1]^[2]^[3].Insertion variations include insertion onto the 2nd rib^[4]^[2].

Nerve

Anterior rami of cervical spinal nerves C3 - C8 ^[1]^[2]^[3].

Artery

The ascending cervical artery branch of the inferior thyroid artery supplies the middle scalene^[2]^[3]^[1].

Function

The middle scalene work with the anterior scalene to elevate the first rib during respiration^[1]^[3] and are also strong ipsilateral flexors during unilateral contraction^[3]^[1]. The middle scalene are also involved with cervical rotation to the opposite side^[3]^[2].

Clinical significance

The interscalene triangle (scalene triangle) is the anatomical triangle formed between the scalenus anterior muscle (anteriorly), the scalenus medius muscle (posteriorly) and the first rib (inferiorly)^[1]^[4]. Structures including the subclavian artery and brachial plexus pass through it^[1]. Abnormal anatomy or injury to this region can cause compression of the neurovascular structures leading to thoracic outlet syndrome (TOS)^[2]^[4]. TOS typically leads to paraesthesia, pain, and weakness in the ipsilateral upper limb^[2].

Assessment

The muscle strength can be tested by having the patient lie supine with arms in 90-degree elbow flexion, and hands resting next to the patient's head. Test the muscle strength by having the patient lift the head in anterolateral flexion. This test is for Scaleni and Sternocleidomastoid muscle strength.^[5]

Treatment

The treatment will depend on the exact diagnosis. Some things to keep in mind are:

References

↑ ^1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 Kenhub 2022, Kenhub: scalene muscles, viewed 16/12/22,https://www.kenhub.com/en/library/anatomy/scalene-muscles
↑ ^2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 Bordoni B, Varacallo M. Anatomy, head and neck, scalenus muscle. StatPearls [Internet]. 2022 Apr 16.
↑ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Anatomy.app 2022, Anatomy.app: Middle scalene, viewed 16/12/22,https://anatomy.app/encyclopedia/middle-scalene
↑ ^4.0 ^4.1 ^4.2 ^4.3 Georgakopoulos B, Lasrado S. Anatomy, Head and Neck, Inter-scalene Triangle. InStatPearls [Internet] 2021 Nov 5. StatPearls Publishing.
↑ Kendall, F.P. Muscles: Testing and Function with Posture and Pain. Lippincott Williams \& Wilkins; 2005

[:0-1] 1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 Kenhub 2022, Kenhub: scalene muscles, viewed 16/12/22,https://www.kenhub.com/en/library/anatomy/scalene-muscles

[:1-2] 2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 Bordoni B, Varacallo M. Anatomy, head and neck, scalenus muscle. StatPearls [Internet]. 2022 Apr 16.

[:2-3] 3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Anatomy.app 2022, Anatomy.app: Middle scalene, viewed 16/12/22,https://anatomy.app/encyclopedia/middle-scalene

[:3-4] 4.0 ^4.1 ^4.2 ^4.3 Georgakopoulos B, Lasrado S. Anatomy, Head and Neck, Inter-scalene Triangle. InStatPearls [Internet] 2021 Nov 5. StatPearls Publishing.

[5] Kendall, F.P. Muscles: Testing and Function with Posture and Pain. Lippincott Williams \& Wilkins; 2005

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