Internal carotid artery

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Internal carotid artery
Blausen 0170 CarotidArteries.png
Gray513.png
Arteries of the neck. The internal carotid arteries arise from the common carotid arteries - labeled Common caroti on the figure.
Details
Precursor 3. Aortic arch
Source Common carotid artery
Branches Ophthalmic, anterior choroidal, anterior cerebral, middle cerebral and posterior communicating artery
Vein Internal jugular vein
Identifiers
Latin arteria carotis interna
MeSH D002343
TA98 A12.2.06.001
TA2 4463
FMA 3947
Anatomical terminology

The internal carotid artery is an artery in the neck which supplies the anterior and middle cerebral circulation. [1]

Contents

In human anatomy, the internal and external carotid arise from the common carotid artery, where it bifurcates at cervical vertebrae C3 or C4. The internal carotid artery supplies the brain, including the eyes, [2] while the external carotid nourishes other portions of the head, such as the face, scalp, skull, and meninges.

Classification

Terminologia Anatomica in 1998 subdivided the artery into four parts: "cervical", "petrous", "cavernous", and "cerebral". [3] [4] In clinical settings, however, usually the classification system of the internal carotid artery follows the 1996 recommendations by Bouthillier, [5] 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 [6] 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, [7] is mainly of historical significance.

Internal carotid artery Circle of Willis 5.jpg
Internal carotid artery

The segments of the internal carotid artery are as follows:

Course/part

Segments of the internal carotid artery, delineated on an MRA of the head. Magnetic resonance angiogram of segments of the internal carotid artery.jpg
Segments of the internal carotid artery, delineated on an MRA of the head.

The internal carotid artery is a terminal branch of the common carotid artery; it arises around the level of the fourth cervical vertebra when the common carotid bifurcates into this artery and its more superficial counterpart, the external carotid artery.

C1: Cervical segment

Level of 6th cervical vertebrae - still at level of common carotid but relationships are similar to those of cervical segment of internal carotid Gray384.png
Level of 6th cervical vertebrae - still at level of common carotid but relationships are similar to those of cervical segment of internal carotid

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 Internal carotid artery.jpg
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

The petrous segment, or C2, of the internal carotid, is that which is inside the petrous part of the temporal bone. This segment extends until the foramen lacerum. The petrous portion classically has three sections: an ascending, or vertical, portion; the genu, or bend; and the horizontal portion.

When the internal carotid artery enters the canal in the petrous portion of the temporal bone, it first ascends a short distance and then curves anteriorly and medially. The artery lies at first in front of the cochlea and tympanic cavity; from the latter cavity it is separated by a thin, bony lamella, which is cribriform in the young subject, and often partly absorbed in old age. Farther forward, it is separated from the trigeminal ganglion by a thin plate of bone, which forms the floor of the fossa for the ganglion and the roof of the horizontal portion of the canal. Frequently this bony plate is more or less deficient, and then the ganglion is separated from the artery by fibrous membrane. The artery is separated from the bony wall of the carotid canal by a prolongation of dura mater and is surrounded by a number of small veins and by filaments of the carotid plexus, derived from the ascending branch of the superior cervical ganglion of the sympathetic trunk.

The named branches of the petrous segment of the internal carotid artery are:

C3: Lacerum segment

The lacerum segment, or C3, is a short segment that begins above the foramen lacerum and ends at the petrolingual ligament, a reflection of periosteum between the lingula and petrous apex (or petrosal process) of the sphenoid bone. The lacerum portion is still considered "extradural" since it is surrounded by periosteum and fibrocartilage along its course. It is erroneously stated in several anatomy textbooks that the internal carotid artery passes through the foramen lacerum. This at best has only ever been a partial truth in that it passes through the superior part of the foramen on its way to the cavernous sinus. As such it does not traverse the skull through it. The inferior part of the foramen is actually filled with fibrocartilage. The broad consensus is that the internal carotid artery should not be described as travelling through the foramen lacerum. [8]

C4: Cavernous segment

Oblique section through the cavernous sinus. Gray571.png
Oblique section through the cavernous sinus.

The cavernous segment, or C4, of the internal carotid artery begins at the petrolingual ligament and extends to the proximal dural ring, which is formed by the medial and inferior periosteum of the anterior clinoid process. The cavernous segment is surrounded by the cavernous sinus.

In this part of its course, the artery is situated between the layers of the dura mater forming the cavernous sinus, but covered by the lining membrane of the sinus. It at first ascends toward the posterior clinoid process, then passes forward by the side of the body of the sphenoid bone, again curves upward on the medial side of the anterior clinoid process, and perforates the dura mater forming the roof of the sinus. The curve in the cavernous segment is called the carotid siphon. This portion of the artery is surrounded by filaments of the sympathetic trunk, and on its lateral side is the abducent nerve, or cranial nerve VI.

The named branches of the cavernous segment are:

The cavernous segment also gives rise to small capsular arteries that supply the wall of the cavernous sinus.

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.

C6: Ophthalmic segment

The ophthalmic artery and its branches Gray514.png
The ophthalmic artery and its branches

The ophthalmic segment, or C6, extends from the distal dural ring, which is continuous with the falx cerebri, to the origin of the posterior communicating artery. The ophthalmic segment courses roughly horizontally, parallel to the optic nerve, which runs superomedially to the carotid at this point.

The named branches of the ophthalmic segment are:

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 internal carotid then divides to form the anterior cerebral artery and middle cerebral artery. The circle of Willis provides a collateral pathway for blood supply to the brain.

Branches

The following are the branches of the internal carotid artery, listed by segment: [9]

Carotid plexus

The sympathetic trunk forms a plexus of nerves around the artery known as the carotid plexus. The internal carotid nerve arises from the superior cervical ganglion, and forms this plexus, which follows the internal carotid into the skull.

Diagnostics

The state and health of internal carotid arteries is usually evaluated using doppler ultrasound, CT angiogram or phase contrast magnetic resonance imaging (PC-MRI).

Typically internal carotid artery blood flow velocities are measured in peak systolic velocity (PSV) and end diastolic velocity (EDV) and according to Society of Radiologists in Ultrasound in healthy subjects without stenosis must be below 125 cm/sec at PSV and below 40 cm/sec at EDV. [10]

One study found that for normative males in the 20-39 age group, PSV averaged 82 cm/sec and EDV 34 cm/sec. In the male 80+ age group, PSV averaged 76 cm/sec and EDV 18 cm/sec. [11]

Additional images

See also

Related Research Articles

Articles related to anatomy include:

<span class="mw-page-title-main">Vertebral artery</span> Major arteries of the neck

The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline basilar artery. As the supplying component of the vertebrobasilar vascular system, the vertebral arteries supply blood to the upper spinal cord, brainstem, cerebellum, and posterior part of brain.

<span class="mw-page-title-main">Ophthalmic artery</span> Artery of the head

The ophthalmic artery (OA) is an artery of the head. It is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the ophthalmic artery supply all the structures in the orbit around the eye, as well as some structures in the nose, face, and meninges. Occlusion of the ophthalmic artery or its branches can produce sight-threatening conditions.

<span class="mw-page-title-main">Common carotid artery</span> One of the two arteries that supply the head and neck with blood

In anatomy, the left and right common carotid arteries (carotids) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.

<span class="mw-page-title-main">Posterior cerebral artery</span> Artery which supplies blood to the occipital lobe of the brain

The posterior cerebral artery (PCA) is one of a pair of cerebral arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.

<span class="mw-page-title-main">Cavernous sinus</span> Sinus in the human head

The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.

<span class="mw-page-title-main">Greater wing of sphenoid bone</span> Large part of the skull front behind the eye socket

The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone, positioned in the skull behind each eye. There is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward.

<span class="mw-page-title-main">Lesser wing of sphenoid bone</span>

The lesser wings of the sphenoid or orbito-sphenoids are two thin triangular plates, which arise from the upper and anterior parts of the body, and, projecting lateralward, end in sharp points [Fig. 1].

<span class="mw-page-title-main">Pterygoid plexus</span>

The pterygoid plexus is a fine venous plexus upon and within the lateral pterygoid muscle. It drains by a short maxillary vein.

<span class="mw-page-title-main">Cavernous nerve plexus</span>

The cavernous nerve plexus is situated below and medial to that part of the internal carotid artery which is placed by the side of the sella turcica in the cavernous sinus, and is formed chiefly by the medial division of the internal carotid nerve.

<span class="mw-page-title-main">Trigeminal ganglion</span> Sensory ganglion of the trigeminal nerve

The trigeminal ganglion is the sensory ganglion of each trigeminal nerve. The trigeminal ganglion is located within the trigeminal cave, a cavity formed by dura mater.

<span class="mw-page-title-main">Carotid canal</span>

The carotid canal is a passage in the petrous part of the temporal bone of the skull through which the internal carotid artery and its internal carotid (nervous) plexus pass from the neck into the cranial cavity.

<span class="mw-page-title-main">Petrous part of the temporal bone</span> Feature at the base of the human skull

The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three angles, and houses in its interior, the components of the inner ear. The petrous portion is among the most basal elements of the skull and forms part of the endocranium. Petrous comes from the Latin word petrosus, meaning "stone-like, hard". It is one of the densest bones in the body. In other mammals, it is a separate bone, the petrosal bone.

<span class="mw-page-title-main">Middle cranial fossa</span>

The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior cranial fossa by the clivus and the petrous crest.

<span class="mw-page-title-main">Inferior cervical ganglion</span>

The inferior cervical ganglion is one of the three cervical sympathetic ganglia. It is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib, on the medial side of the costocervical artery.

<span class="mw-page-title-main">Body of sphenoid bone</span>

The body of the sphenoid bone, more or less cubical in shape, is hollowed out in its interior to form two large cavities, the sphenoidal sinuses, which are separated from each other by a septum.

<span class="mw-page-title-main">Base of skull</span> Inferior area of the skull, composed of the endocranium and lower parts of the skull roof

The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

<span class="mw-page-title-main">Parapharyngeal space</span>

The parapharyngeal space, is a potential space in the head and the neck. It has clinical importance in otolaryngology due to parapharyngeal space tumours and parapharyngeal abscess developing in this area. It is also a key anatomic landmark for localizing disease processes in the surrounding spaces of the neck; the direction of its displacement indirectly reflects the site of origin for masses or infection in adjacent areas, and consequently their appropriate differential diagnosis.

References

PD-icon.svgThis article incorporates text in the public domain from page 566 of the 20th edition of Gray's Anatomy (1918)

  1. "Carotid artery". WebMD. Retrieved 28 July 2015.
  2. Kiel JW (2010). "The Ocular Circulation". Integrated Systems Physiology: From Molecule to Function to Disease. 3: 1–81. doi:10.4199/C00024ED1V01Y201012ISP012. PMID   21452447. The arterial input to the eye is provided by several branches from the ophthalmic artery, which is derived from the internal carotid artery in most mammals.
  3. "Internal Carotid Artery". www.meddean.luc.edu. Retrieved 2021-07-09.
  4. "Internal carotid artery" at Dorland's Medical Dictionary
  5. Bouthillier, Alain; Harry van Loveren; Jefferey Keller (March 1996). "Segments of the internal carotid artery: a new classification". Neurosurgery. 38 (3): 425–432. doi:10.1097/00006123-199603000-00001. PMID   8837792.
  6. Lasjaunias P, Santoyo-Vazquez A. Segmental agenesis of the internal carotid artery: angiographic aspects with embryological discussion. Anat Clin 1984;6:133–41
  7. Fischer E. Die Lageabweichungen der vorderen Hirnarterie im Gefa¨ssbild. Zentralbl Neurochir 1938;3:300 –13
  8. TAUBER M, VAN LOVEREN H. R et al. The enigmatic foramen lacerum. Commentaries. Neurosurgery. 1999, vol. 44, no2, pp. 386-393
  9. Osborn, Anne (1999). Diagnostic Cerebral Angiography (2nd ed.). Philadelphia, PA, USA: Lippincott Williams & Wilkins. ISBN   0-397-58404-0.
  10. Weerakkody, Yuranga. "Ultrasound assessment of carotid arterial atherosclerotic disease | Radiology Reference Article | Radiopaedia.org". Radiopaedia. Retrieved 2024-03-08.
  11. "Blood-flow velocities and their relationships in carotid and middle cerebral arteries".