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Topic

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Occipital bone

The occipital bone is a flat, trapezoidal cranial bone forming the posterior and inferior part of the skull. It articulates with the parietal bones at the lambdoid suture, the temporal bones at the occipitomastoid sutures, and the sphenoid bone anteriorly. The occipital bone also surrounds and protects the foramen magnum, through which the medulla oblongata and vertebral arteries pass. It consists of four main regions: the squamous part, the basilar part, and the two lateral parts, each contributing to the skull’s shape, structural stability, and attachment sites for muscles and ligaments. The external surface provides attachments for neck and posterior scalp muscles, while the internal surface houses the posterior cranial fossa accommodating the cerebellum and brainstem.

Synonyms

  • Os occipitale

  • Occiput

  • Posterior cranial bone

Function

  • Protects the posterior portion of the brain including the cerebellum and occipital lobes

  • Forms the foramen magnum, allowing passage of the spinal cord and vertebral arteries

  • Provides attachment sites for neck and posterior scalp muscles

  • Contributes to the structural integrity and shape of the skull

MRI Appearance
T1-weighted images:

  • The occipital bone appears low signal intensity (hypointense) due to its cortical bone composition

  • Bone marrow within the diploë may appear intermediate to slightly hyperintense, depending on age and fat content

  • Surrounding soft tissues, including muscles and subcutaneous fat, provide contrast with hyperintense signal

T2-weighted images:

  • Cortical bone remains hypointense

  • Bone marrow may show intermediate signal, while adjacent CSF and fat are hyperintense

  • Useful for detecting bone marrow edema, fractures, or neoplastic infiltration

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal, highlighting pathology in bone marrow

  • Normal cortical bone remains hypointense, while edema, inflammation, or tumors appear hyperintense

CT Appearance

  • The occipital bone appears as a hyperdense cortical shell surrounding the diploic space, which has intermediate density

  • The foramen magnum, occipital condyles, and external protuberances are clearly visualized

  • Air in adjacent structures (nasopharynx, mastoid air cells) appears hypodense, enhancing anatomical contrast

  • CT is ideal for fracture detection, congenital anomalies, and preoperative planning

MRI images

Occipital bone mri axial image -img-00000-00000

CT VRT 3D image

Occipital bone

X ray image

X ray Occipital bone anatomy image -img-00000-00000