page_title: Internal carotid artery
section_title: Classification
hierarchical_section_title: Internal carotid artery / Classification
caption_attribution_description: English: Circle of Willis
context_page_description: The internal carotid artery is located in the inner side of the neck in contrast to the external carotid artery. In human anatomy, they arise from the common carotid arteries where these bifurcate into the internal and external carotid arteries at cervical vertebral level 3 or 4; the internal carotid artery supplies the brain including eyes, while the external carotid nourishes other portions of the head, such as face, scalp, skull, and meninges.
context_section_description: Terminologia Anatomica in 1998 subdivided the artery into four parts: "cervical", "petrous", "cavernous", and "cerebral". However, in clinical settings, the classification system of the internal carotid artery usually follows the 1996 recommendations by Bouthillier, describing seven anatomical segments of the internal carotid artery, each with a corresponding alphanumeric identifier—C1 cervical, C2 petrous, C3 lacerum, C4 cavernous, C5 clinoid, C6 ophthalmic, and C7 communicating. The Bouthillier nomenclature remains in widespread use by neurosurgeons, neuroradiologists and neurologists. The segments are subdivided based on anatomical and microsurgical landmarks and surrounding anatomy, more than angiographic appearance of the artery.  An alternative embryologic classification system proposed by Pierre Lasjaunias  and colleagues is invaluable when it comes to explanation of many internal carotid artery variants. An older clinical classification, based on pioneering work by Fischer, is mainly of historical significance.
  The segments of the internal carotid artery are as follows:
  Cervical segment, or C1, identical to the commonly used Cervical portion
  Petrous segment, or C2
  Lacerum segment, or C3
  C2 and C3 compose the commonly termed Petrous portion
  Cavernous segment, or C4, almost identical to the commonly used Cavernous portion
  Clinoid segment, or C5. This segment is not identified in some earlier classifications and lies between the commonly used cavernous portion and cerebral or supraclinoid portion.
  Ophthalmic, or supraclinoid segment, or C6
  Communicating, or terminal segment, or C7
  C6 and C7 together constitute the commonly used cerebral or supraclinoid portion.
caption: Internal carotid artery
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