internal_carotid_artery_segments

Internal carotid artery segments


The course of the internal carotid artery (ICA) and its segment classifications were reviewed by means of a new and freely available interactive 3D model of the artery and the skull base, based on human neuroimages, that can be freely downloaded at the Public Repository of the University of Barcelona ( http://diposit.ub.edu/dspace/handle/2445/112442 ) and runs under Adobe Acrobat Reader in Mac and Windows computers and Windows 10 tablets. The 3D-PDF allows zoom, rotation, selective visualization of structures, and a predefined sequence view. Illustrative images of the different classifications were obtained 1).

Fisher's classification

Gibo classification

Bouthillier classification.

C1: Cervical segment Bouthillier and Gibo


Begins in neck at carotid bifurcation where the common carotid artery divides into internal carotid artery and external carotid artery. Travels in carotid sheath with IJV and vagal nerve, encircled with postganglionic sympathetic nerves (PGSN). C1 ends where the ICA enters carotid canal of petrous bone. No branches

The cervical segment, or C1, or cervical part of the internal carotid, extends from the carotid bifurcation until it enters the carotid canal in the skull anterior to the jugular foramen.

Internal carotid artery - dissection At its origin, the internal carotid artery is somewhat dilated. This part of the artery is known as the carotid sinus or the carotid bulb. The ascending portion of the cervical segment occurs distal to the bulb, when the vessel walls are again parallel.

The internal carotid runs vertically upward in the carotid sheath and enters the skull through the carotid canal. During this part of its course, it lies in front of the transverse processes of the upper three cervical vertebrae.

It is relatively superficial at its start, where it is contained in the carotid triangle of the neck, and lies behind and medial to the external carotid, overlapped by the sternocleidomastoid muscle, and covered by the deep fascia, the platysma, and integument: it then passes beneath the parotid gland, being crossed by the hypoglossal nerve, the digastric muscle and the stylohyoid muscle, the occipital artery and the posterior auricular artery. Higher up, it is separated from the external carotid by the styloglossus and stylopharyngeus muscles, the tip of the styloid process and the stylohyoid ligament, the glossopharyngeal nerve and the pharyngeal branch of the vagus nerve. It is in relation, behind, with the longus capitis, the superior cervical ganglion of the sympathetic trunk, and the superior laryngeal nerve; laterally, with the internal jugular vein and vagus nerve, the nerve lying on a plane posterior to the artery; medially, with the pharynx, superior laryngeal nerve, and ascending pharyngeal artery. At the base of the skull the glossopharyngeal, vagus, accessory, and hypoglossal nerves lie between the artery and the internal jugular vein.

Unlike the external carotid artery, the internal carotid normally has no branches in the neck.

C2: Petrous segment

C3 segment of the internal carotid artery

Internal carotid artery C4 segment

C5: Clinoid segment The clinoid segment, or C5, is another short segment of the internal carotid that begins after the artery exits the cavernous sinus at the proximal dural ring and extends distally to the distal dural ring, after which the carotid artery is considered “intra-dural” and has entered the subarachnoid space.

The clinoid segment normally has no named branches, though the ophthalmic artery may arise from the clinoid segment.

Internal carotid artery C6 segment

C7: Communicating segment The communicating segment, or terminal segment, or C7, of the internal carotid artery passes between the optic and oculomotor nerves to the anterior perforated substance at the medial extremity of the lateral cerebral fissure. Angiographically, this segment extends from the origin of the posterior communicating artery to the bifurcation of the internal carotid artery.

The named branches of the communicating segment are:

the posterior communicating artery the anterior choroidal artery The internal carotid then divides to form the anterior cerebral artery and middle cerebral artery. The internal carotid artery can receive blood flow via an important collateral pathway supplying the brain, the cerebral arterial circle, which is more commonly known as the Circle of Willis.

The Kassam's group (2014), with an endoscopic endonasal perspective, introduces the “paraclival segment,” including the “lacerum segment” and part of the intracavernous ICA, and details surgical landmarks to minimize the risk of injury 2).

see also Carotid Siphon

AC: anterior clinoid process; ICA: internal carotid artery; LT: lamina terminalis; ON: optic nerve; OlN; olfactory nerve; SW: sphenoid wing; TS: tuberculum sellae; A1: A1 segment of the Anterior Cerebral Artery; A2: A2 segment of the Anterior Cerebral Artery; M1: M1 segment of the Middle Cerebral Artery

Based on anatomic correlations, the ICA may be described as 6 distinct segments:

(1) parapharyngeal (common carotid artery bifurcation to carotid canal)

(2) petrous (carotid canal to posterolateral aspect of foramen lacerum)

(3) paraclival (posterolateral foramen lacerum to the superomedial aspect of the petrous apex)

(4) parasellar (superomedial petrous apex to the proximal dural ring)

(5) paraclinoid (from the proximal to the distal dural rings)

(6) intradural (distal ring to ICA bifurcation).

Corresponding surgical landmarks included the Eustachian tube, the fossa of Rosenmüller, and levator veli palatini for the parapharyngeal segment; the vidian canal and V3 for the petrous segment; the fibrocartilage of foramen lacerum, foramen rotundum, maxillary strut, lingular process of the sphenoid bone, and paraclival protuberance for the paraclival segment; the sellar floor and petrous apex for the parasellar segment; and the medial and lateral opticocarotid and lateral tubercular recesses, as well as the distal osseous arch of the carotid sulcus for the paraclinoid segment 3).

see Intracavernous internal carotid artery.


1)
Melé MV, Puigdellívol-Sánchez A, Mavar-Haramija M, Juanes-Méndez JA, Román LS, De Notaris M, Catapano G, Prats-Galino A. Review of the main surgical and angiographic-oriented classifications of the course of the internal carotid artery through a novel interactive 3D model. Neurosurg Rev. 2018 Jul 26. doi: 10.1007/s10143-018-1012-7. [Epub ahead of print] Review. PubMed PMID: 30051302.
2) , 3)
Labib MA, Prevedello DM, Carrau R, Kerr EE, Naudy C, Abou Al-Shaar H, Corsten M, Kassam A. A road map to the internal carotid artery in expanded endoscopic endonasal approaches to the ventral cranial base. Neurosurgery. 2014 Sep;10 Suppl 3:448-71. doi: 10.1227/NEU.0000000000000362. PubMed PMID: 24717685.
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