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Carotid canal

The carotid canal is a bony passage within the petrous part of the temporal bone of the skull. It serves as the entry point for the internal carotid artery (ICA) into the cranial cavity, as well as the accompanying sympathetic nerve plexus. The canal has a characteristic curved trajectory and is an important anatomical landmark in head and neck imaging due to its close relationship with several critical neurovascular structures. Accurate identification and assessment of the carotid canal are crucial in evaluating trauma, tumors, and vascular pathologies.

MRI Appearance of the Carotid Canal

  • T1-Weighted Images

    • The carotid canal itself appears as a well-defined, low-signal (dark) tubular structure due to the presence of cortical bone.

    • The internal carotid artery within the canal typically appears as a flow void (very low signal) due to the fast-moving blood.

    • Surrounding bone marrow of the temporal bone may show intermediate to high signal.

  • T2-Weighted Images

    • The bony walls of the carotid canal remain hypointense (dark) on T2.

    • The internal carotid artery may again be seen as a signal void, surrounded by a hyperintense (bright) cerebrospinal fluid (if imaged closely to the petrous apex).

    • The adjacent bone marrow can be moderately hyperintense.

  • STIR (Short Tau Inversion Recovery) Images

    • The bony canal is hypointense (dark), consistent with all MRI sequences.

    • The STIR sequence suppresses fat, so marrow fat signal is reduced, making the bony canal margins even more distinct.

    • The internal carotid artery may be visualized as a signal void.

    • Useful in evaluating for marrow or soft tissue edema (such as in fracture, infection, or tumor extension).

CT Appearance of the Carotid Canal

  • The carotid canal is seen as a round or oval, well-circumscribed bony tunnel within the petrous temporal bone.

  • Best visualized on thin-section axial and coronal bone window images.

  • Internal carotid artery may be seen as a soft tissue density within the canal, especially with contrast.

  • The canal is bordered by dense cortical bone, which appears bright (white) on CT.

MRI images

Carotid canal mri axial image -img-00000-00000