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Dorsal scapular nerve

The dorsal scapular nerve (DSN) is a motor branch of the C5 nerve root from the brachial plexus. It primarily supplies the levator scapulae, rhomboid minor, and rhomboid major muscles, which function to elevate and retract the scapula.

The nerve pierces the middle scalene muscle soon after its origin, then travels deep to the levator scapulae, running along the medial border of the scapula in association with the dorsal scapular artery. It is an important nerve in scapular movement and posture, and its injury may lead to scapular winging or weakness of shoulder retraction.

Synonyms

  • Nerve to rhomboids

  • Posterior scapular nerve

Origin and Course

  • Origin: From the ventral ramus of the C5 nerve root, occasionally with contributions from C4.

  • Course:

    • Arises near the upper trunk of the brachial plexus.

    • Passes posteriorly through the middle scalene muscle (a common site of entrapment).

    • Descends deep to the levator scapulae muscle and continues along the medial border of the scapula, deep to the rhomboids.

    • Accompanies the dorsal scapular artery along its course.

  • Termination: Ends by supplying the rhomboid major muscle near the inferior angle of the scapula.

Relations

  • Anteriorly: Middle scalene muscle (which it pierces).

  • Posteriorly: Deep surface of levator scapulae and rhomboid muscles.

  • Laterally: Brachial plexus roots and trunks.

  • Medially: Medial border of scapula and dorsal thoracic wall.

  • Superiorly: Cervical plexus and spinal accessory nerve (CN XI).

  • Inferiorly: Serratus posterior superior muscle.

Branches and Distribution

  • Muscular branches:

    • To levator scapulae (upper branch).

    • To rhomboid minor and major (lower branches).

  • Sensory fibers: Usually absent, but may carry proprioceptive input from shoulder girdle muscles.

Function

  • Motor:

    • Rhomboid major and minor: Retract and rotate the scapula medially, stabilizing it against the thoracic wall.

    • Levator scapulae: Elevates and rotates the scapula downward.

  • Postural support: Maintains scapular alignment during arm movements.

  • Functional integration: Works with trapezius and serratus anterior to coordinate scapular motion during shoulder elevation and rotation.

Clinical Significance

  • Dorsal scapular neuropathy: Caused by entrapment in the middle scalene or trauma. Presents with pain, weakness, or atrophy of rhomboids.

  • Scapular winging: Medial border prominence due to rhomboid weakness (distinct from long thoracic nerve palsy).

  • Overuse injury: Common in throwing athletes, weightlifters, or those with poor posture.

  • Cervical radiculopathy: C5 root compression can secondarily affect the DSN.

  • Surgical relevance: Important to identify and preserve during posterior cervical or scapular surgery.

MRI Appearance

  • T1-weighted images:

    • Nerve: Slender low-to-intermediate signal structure within the fat plane posterior to the scalene and scapular muscles.

    • Surrounding fat: Bright signal aiding visualization.

    • Muscle targets: Levator scapulae and rhomboids normally intermediate signal with clear fascicular pattern.

    • Pathology: Denervation shows muscle hyperintensity or fatty infiltration on T1.

  • T2-weighted images:

    • Nerve: Intermediate-to-low signal line within perineural fat.

    • Acute neuropathy: High T2 hyperintensity and mild enlargement of the nerve.

    • Muscle changes: Edema and early denervation appear bright hyperintense in affected muscles.

  • STIR:

    • Normal nerve: Intermediate-to-dark signal.

    • Pathology: Bright hyperintensity indicates neuritis or entrapment.

    • Muscles: Hyperintense edema within levator scapulae or rhomboids suggests recent denervation.

  • Proton Density Fat-Saturated (PD FS):

    • Normal nerve: Low to intermediate signal.

    • Abnormal nerve: Focal bright signal in neuritis or entrapment.

    • Muscle: Hyperintensity in early denervation phase; chronic denervation shows signal drop with volume loss.

  • T1 Fat-Sat Post-Contrast:

    • Normal nerve: Minimal or no enhancement.

    • Inflamed or compressed nerve: Linear or nodular enhancement.

    • Denervated muscle: May enhance due to vascular proliferation or inflammation.

CT Appearance

Non-Contrast CT:

  • Nerve: Not directly visualized but inferred by the fat plane path along the medial scapula.

  • Indirect signs: Muscle asymmetry or atrophy of rhomboids or levator scapulae.

  • Bone changes: May show chronic scapular malposition or hypertrophic bone after repetitive traction injury.

MRI image

Dorsal scapular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Dorsal scapular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001