Scalene Muscles

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The Scalene muscle group is made up of the Scalenus anterior, Scalenus medius, Scalenus posterior, and Scalenus minimus.

Scalenus Anterior

The Scalenus anterior is a lateral muscle of the neck.

Anatomical Attachments:

• Origin: Attaches to the anterior tubercles of the transverse processes of C3 through C6 vertebra.
• Insertion: Attaches to the ridge on the superior surface of the 1st rib.

Action: When it is acting superiorly, it elevates the 1st rib and when it is acting inferiorly, it flexes and rotates the cervical column.

Nerve Supply: Anterior branches of the Cervical nerves 5 through 8.

Vascular supply: Ascending cervical branch of the inferior thyroid artery.

Scalenus Medius

The Scalenus Medius is a lateral muscle of the neck.

Anatomical Attachments:

• Origin: Attaches to the posterior tubercles of transverse processes of C2 through C7.
• Insertion: Attaches to the superior surface of the 1st rib behind the subclavian groove.

Action: When it is acting superiorly, it elevates 1st rib as in the process of inhalation; inferiorly, assists in flexion and rotation of the neck.

Nerve Supply: Posterior and lateral branches of Cervical nerves 3 and 4.

Vascular supply: Muscular branches of the ascending cervical artery.

Scalenus Posterior

The Scalenus posterior is a lateral muscle of the neck.

Anatomical Attachments:

• Origin: Attaches to the posterior tubercles of the transverse processes of C4, C5 and C6.
• Insertion: Attaches to the anterior surface of the 2nd rib.

Action: When it is acting superiorly, elevates the 2nd rib and assists in respiration; singularly, laterally flexes and rotates the cervical column; bilaterally, forward flexes the cervical column.

Nerve Supply: Cervical nerves 3 and 4.

Vascular supply: Muscular branches of the ascending inferior thyroid artery and superficial branch of the transverse cervical artery.

Scalenus Minimus

The Scalenus minimus is an anterior muscle of the neck.

Anatomical Attachments: According to Travell and Simons, this muscle is absent in a large percentage of the population. It lies posterior to the subclavian artery, underneath the inferior aspect of the Scalenus anterior.

• Origin: Extends from the transverse process of the 7th cervical vertebrae
• Insertion: Attaches to the fascia supporting the dome of the pleura and inner border of the 1st rib.

Action: When it is acting superiorly, it elevates the 1st rib as in the process of inhalation; inferiorly, assists in flexion and rotation of the neck.

Nerve Supply: Cervical nerve 7.

Vascular supply: Muscular branches of the ascending Cervical artery.

Scalene Muscle Group

Synergist: Sternocleidomastoid, Longus colli and capitis

Antagonist: Semispinalis capitis and cervicis, Splenius capitis and cervicis, Spinalis cervicis, Interspinales, Longissimus cervicis, Iliocostalis cervicis, Multifidus.

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Nerve Entrapment: Most authors readily acknowledge that the abnormal shortening of the scalene muscles elevate the first rib, thus, producing a compressive force on the Thoracic outlet and impinging the subclavian artery and the brachial plexus. Discussed far less, are the mechanical influences of the Scalenes on the cervical plexus. While it is acknowledged that the cervical plexus lies deep to the SCM; hypertonic Scalenes may also cause an impingement force on the numerous nerves leaving this plexus. This could possibly cause a direct entrapment of the cervical plexus, as well as an indirect influence of the thoracic outlet. Travell and Simons discovered triggers within the Scalenes that have referral patterns similar to the referral of a Thoracic Outlet Syndrome (TOS). They reference this TrP referral, as well as triggers found in the Pectoralis major, Subscapularis and others, as a Pseudo Thoracic Outlet Syndrome. However, according to most authors, Scalene entrapment represents the mechanical compressive influence of the Scalenes to impinge the subclavian artery and brachial nerve by reducing the thoracic outlet and is referenced as Scalenus anticus or Costoclavicular syndromes. While exceedingly rare, a seventh cervical rib could be responsible for these symptoms of loss sensation and/or pain of the shoulder, arm, forearm and wrist. This Thoracic outlet compression is known as Cervical rib syndrome. To distinguish between a Thoracic outlet syndrome and a Pseudo Thoracic outlet syndrome, the practitioner should perform an Adsons Test or Maneuver, in addition to radiographs for cervical rib and/or vertebral stenosis. Additional considerations for this condition would be a radiculopathy of C5 through C8. Subclavian or Brachial artery occlusion is secondary to thrombosis. With swelling, consider Scalene or axillary compression of lymphatics or Lymphadenopathy. With difficulty breathing, swallowing and/or reduced cervical rotation; consider Cervical plexus compression and/or lower cervical segmental dysfunction.

• Primary: Primary: Posteriorly – The pain refers across the superior half of the vertebral border of the scapula to the shoulder region, which extends down the arm to the wrist, thumb, and index and middle fingers. Anteriorly – The pain traverses down the chest, and according to Travell and Simons, divides into two fingerlike projections toward the nipple. When the Scalenus minimus exists, the pain referral from an active TrP initiates at approximately the deltoid tuberosity, traverses posteriorly and inferiorly toward the lateral aspect of the elbow, but omits the elbow, to traverse posteriorly along the dorsum of the forearm into all five fingers with the predominant pain being experienced in the dorsum of the thumb.
• Satellite or associated triggers: Pectoralis major and minor, Triceps brachii, Deltoid, Extensor Carpi ulnaris, Extensor Digitorum, Brachioradialis, Omohyoid, upper Trapezius, Sternocleidomastoid, Splenius capitis.

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Trigger Point Signs and Symptoms: Shoulder and upper limb pain, muscle tenderness, venous obstruction, vasomotor changes, spasm, chest pain, back pain which is located predominantly at the vertebral border of the ipsilateral scapula, paresthesia with possible swelling of the hand.

Trigger Point Activating and Perpetuating Factors: Trauma, excessive pulling or lifting, paradoxical breathing, upper limb amputation, Scoliosis, and acceleration/deceleration injury.

Differential Diagnosis: (Segmental, Subluxation, Somatic dysfunction) C4 C5 C6 C7 or C8 radiculopathy, Cervical spine articular dysfunction, Thoracic outlet syndrome (Scalenus anticus syndrome, Costoclavicular syndrome or Cervical rib syndrome), Myofascial Pseudo Thoracic outlet syndrome, Coracoid pressure syndrome, Angina pectoris, Carotid or Subclavian artery occlusion, Myocardial infarction, Spinal cord and/or Lymphatic cervical chain tumors, Multiple sclerosis, Subacromial or Bicipital tendinitis, Tendinitis, Lateral epicondylitis, Subacute meningitis or Peripheral neuropathy, Polyneuropathy, Polymyalgia rheumatica, Eosinophilic fasciitis, Fibromyalgia, Spasmodic torticollis (Wryneck syndrome), Tetanus, Stinger or Burner, Frostbite, Carpal tunnel syndrome, Systemic infections or inflammation, Nutritional inadequacy, Metabolic imbalance, Toxicity, Side effects of medication.

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