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Splenius capitis muscle

The splenius capitis is a broad, strap-like muscle located in the posterior aspect of the neck. It plays a crucial role in movements and stability of the head and upper cervical spine. This muscle is part of the superficial layer of the intrinsic back muscles, forming part of the muscular contour at the back of the neck. Knowledge of its anatomy, function, and imaging characteristics is essential in clinical neurology, orthopedics, and radiology.

Anatomy of Splenius Capitis Muscle

  • Function:

    • Acts to extend, rotate, and laterally flex the head and neck.

    • Bilateral contraction extends the head and neck.

    • Unilateral contraction results in lateral flexion and rotation of the head to the same side.

  • Origin:

    • Lower half of the ligamentum nuchae

    • Spinous processes of C7 (7th cervical) to T3/T4 (3rd/4th thoracic) vertebrae

  • Insertion:

    • Mastoid process of the temporal bone

    • Lateral third of the superior nuchal line of the occipital bone

  • Nerve Supply:

    • Posterior rami of the middle cervical spinal nerves (mainly C3 and C4)

  • Artery Supply:

    • Branches from the occipital artery

    • Branches from the deep cervical artery

  • Vein Supply:

    • Veins drain into the occipital vein and deep cervical vein

Imaging Appearance

  • MRI Appearance:

    • T1-weighted:

      • Intermediate to low signal intensity compared to surrounding fat

      • Good muscle-to-fat contrast

    • T2-weighted:

      • Normal muscle demonstrates relatively low signal intensity, but increased signal may indicate edema or pathology.

    • STIR (Short Tau Inversion Recovery):

      • Muscle appears dark, but areas of edema/inflammation are hyperintense (bright)

  • CT Appearance:

    • Appears as a well-defined, soft-tissue structure posterior and lateral to the cervical vertebrae

    • Muscle density is higher than surrounding fat

MRI images

Splenius capitis muscle mri axial image