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Obliquus inferior capitis muscle

The Obliquus Inferior Capitis muscle—also known as the Inferior Oblique Muscle of the Head—is a small, thick muscle located in the suboccipital region of the neck. It plays a crucial role in head and neck movement, specifically rotation of the atlas (C1 vertebra) on the axis (C2 vertebra). This muscle is a key component of the suboccipital triangle and is essential in clinical and radiological anatomy due to its involvement in head posture and proximity to important neurovascular structures.

Synonyms:

  • Inferior oblique muscle of the head

  • Obliquus capitis inferior

  • Suboccipital inferior oblique muscle

Function:

  • Rotates the atlas (C1 vertebra) and, by extension, the head to the same (ipsilateral) side

  • Stabilizes the atlantoaxial joint during head movements

  • Assists in proprioception of the upper cervical region

Origin:

  • Spinous process of the axis (C2 vertebra)

Insertion:

  • Transverse process of the atlas (C1 vertebra)

Nerve Supply:

  • Suboccipital nerve (dorsal ramus of C1)

Artery Supply:

  • Vertebral artery (muscular branches)

  • Occipital artery (muscular branches)

Vein Supply:

  • Vertebral vein

  • Occipital vein

MRI Appearance:

  • T1-weighted images: Appears isointense to other skeletal muscles, showing intermediate signal intensity.

  • T2-weighted images: Also isointense to skeletal muscle; pathology (e.g., edema, denervation) increases signal.

  • STIR (Short Tau Inversion Recovery): Normal muscle appears dark; high signal (bright) indicates edema or acute pathology.

CT Appearance:

  • Appears as a soft tissue density muscle in the suboccipital triangle, lateral and inferior to the rectus capitis posterior major.

  • Normal muscle is homogenous and well-defined; atrophy or edema alters appearance.

MRI images

Obliquus inferior capitis muscle mri axial image