Radiological vascular anatomy of the head and neck.

Dr/ ABD ALLAH NAZEER. MD.

Introduction to Brain Anatomy.The brain is subdivided into structure, vasculature, and connections (white matter tracts); consequently, we consider structural, vascular, and connectional neuroanatomies.

3D cerebral models of structure, vasculature, and tracts are mutually consistent because they were derived from the same brain specimen.

• 3D cerebral models and the planar images are fully parcellated; each parcellated object is uniquely colored.

• 3D cerebral models and the planar images are completely labeled; as a terminology, we use the Terminologia Anatomica.

• 3D cerebral models are electronically dissectible into groupsand individual components.

The CNS consists of the brain and the spinal cord. The brain encases the fluid-filled ventricular system and is parcellated into three main components:• Cerebrum• Cerebellum (the little brain)• BrainstemThe cerebrum comprises:• Left and right cerebral hemispheres• Interbrain between the cerebrum and the brainstem termed the

diencephalon.• Deep gray nucleiThe cerebral hemispheres are the largest compartment of the brain and are interconnected by white matter fibers. The hemispheres are composed of:

• Outer gray matter termed the cerebral cortex• Inner white matter encompassing the deep gray nuclei

MR-angiography of the aortic arch and head & neck arterial vessels overview.

Vascular Anatomy.

The cerebral vasculature with arteries, veins, and dural sinuses. The vessels are uniquely color-coded such that all vessels with the same name have the same color

Normal vascular anatomy of the head and neck is rich and highly detailed, precise knowledge has use in reporting vascular pathology but also in defining conditions that secondarily affects or displace arteries and veins.

Aortic arch : begins at the level of the upper border of the second sternocostal articulation on the right, runs upward, backward and ends to the left from the trachea; then downward on the left side of T4 vertebral body (from here starts the descending aorta).From the aortic arch originate:• innominate artery: right subclavian artery, right carotid artery• left carotid artery• left subclavian arterySuperior vena cava, formed by the left and the right brachiocephalic veins, is located right from the ascending aorta.Normal anatomy on axial CT scans shows the three arterial vessels (innominate, left carotid, left subclavian) in a row from right to left. Right most is the superior vena cava, and anterior is the left innominate veins.

The configuration here described is the most common (~80%) but variants are frequent: common origin of innominate and left carotid artery <3% (so called "bovine arch"), variants of origin of the vertebral artery (most often left vertebral artery from the aortic arch)~4%, thyroid ima artery, aberrant right subclavian artery~1% (it is the last branch of the aortic arch and crosses behind the esophagus most often), so called "arteria lusoria".Many, less common, variants exist.Clinical interest for aortic arch anatomy in H&N, beside being the origin of the main neck arterial vessels is related to the path of recurrent (inferior) laryngeal nerve, branch of the X c.n., vagus nerve. It is so called "recurren" because it descends into the thorax before rising up between trachea and esophagus. The right nerve loops around the right subclavian artery, while he left has a longer course as it hooks the aortic arch.The recurrent (inferior) laryngeal nerve is responsible for supplying all laryngeal muscles (except the cricothyroid, which is innervated by the superior laryngeal nerve). Damage to recurrent laryngeal nerve results in ipsilateral vocal cord paralysis. Left recurrent laryngeal nerve damage can result from enlarged thoracic lymph nodes, direct tumoral invasion, aortic aneurysm. Higher in the neck both recurrent laryngeal nerve are at risk of injury during neck/thyroid surgery as they run immediately posterior to this gland.

Subclavian artery: is located between the anterior scalene

muscle and the mediusscalene muscle, while the subclavian vein is located anterior to the anterior scalene muscle. Both are deep to the sternocleidomastoid muscle.

The subclavian artery can be divided into three segments:• 1st segment, from the origin to the medial border of anterior scalene muscle. Branches: vertebral artery, internal mammary artery (runs downward posterior to the ribs), thyrocervical trunk: inferior thyroid artery, ascending cervical artery, transverse cervical artery).• 2nd segment, posterior to the anterior scalene muscle. Branches:costocervical trunk, gives off intercostal arteries, and deep cervical artery which can give anastomosis with the vertebral circulation.• 3rd segment, from the lateral border of the anterior scalene muscle to the esternal border of the 1st rib (from here it becomes axillary artery).

Branches: dorsal artery of the scapula.

Vertebral arteries: arise from the subclavian artery (1st

segment) then move medially to the transverse process at the level of C6 (variant 8% at C7) and start to move upward crossing multiple transverse foramina of each vertebrae until C1. At the level of the atlas bone vertebral arteries travel across the posterior arch entering the foramen magnum.• V1: from the origin to the transverse foramen.• V2: from the lowest transverse foramen to C2.• V3: from C2 to the dura, crossing the foramen magnum.• V4: from dura to basilar artery.The vertebral arteries are commonly of unequal caliber, typically the left is larger(dominant left).Vertebral arteries do not give relevant branches is the H&N region (except potential anastomosis).

Carotid arteries:• Common carotid artery (CC)• Internal carotid artery (ICA)• External carotid artery (ECA)

The internal carotid artery (ICA) branches into the anterior cerebral artery and the middle cerebral artery. The left and right posterior cerebral arteries originate from the basilar artery

Anterior Cerebral ArteryThe anterior cerebral artery has the following main branches:• A1 segment ( precommunicating part)• A2 segment ( postcommunicating part)–– Pericallosal artery–– Callosomarginal artery

Middle Cerebral ArteryThe middle cerebral artery is subdivided into four segments (Fig. 2.19a):• M1 segment (sphenoid part)• M2 segment (insular part)• M3 segment (opercular part)• M4 segment (terminal part)

Posterior Cerebral ArteryThe posterior cerebral artery is parcellated into four segments:• P1 segment (precommunicating part)• P2 segment (postcommunicating part)• P3 segment (lateral occipital artery)• P4 segment (medial occipital artery)

Circle of WillisThe circle of Willis connects the anterior and posterior circulations.It includes the following vessels:

• Anterior communicating artery• Left and right posterior communicating arteries• Part of the left and right internal carotid arteries• Left and right A1 segments of the anterior cerebral arteries• Left and right P1 segments of the posterior cerebral arteries

External carotid artery (ECA)ECA is the major artery of H&N and begins at the level of the upper border of thyroid cartilage, taking a slightly curved course, passes upward and forward, and then inclines backward to the space behind the neck of the mandible, where it divides into the superficial temporal and maxillary artery within the parotid gland.Eight branches feed the scalp, face and deep structures, and can be divided into 4 groups:

Anterior• lingual artery • superior thyroid artery• facial artery

Middle• ascending pharyngeal artery

Posterior• occipital artery• deep auricular artery

Terminal• internal maxillary artery• superficial temporal artery

Venous system.The main component of the venous system are:Dural sinuses Cerebral veins–– Superficial veins–– Deep veinsThe cerebral veins empty into the dural sinuses.

The main dural sinuses are:• Superior sagittal sinus• Inferior sagittal sinus• Straight sinus• Left and right transverse sinuses• Left and right sigmoid sinuses

Cerebral VeinsThe main superficial cerebral veins are:• Frontopolar veins• Prefrontal veins• Frontal veins• Parietal veins• Occipital veins

Great vein (of Galen)• Left and right basal vein (of Rosenthal)• Left and right internal cerebral veins

Axial image, normal aortic arch configuration from right to left (red lines):innominate artery, left carotid artery, left subclavian artery. On the right (blue lines) superior vena cava and anterior left innominate vein.

Axial image at the level of T5, shows approximate position of descending and ascending left recurrent laryngeal nerve as it hooks the aortic arch.

Coronal image shows right subclavian artery located between the anterior scalenemuscle and the medius scalene muscle. Relationship with the 1st rib is also clear. The mentioned structured are also used to divide the subclavian artery into three segments

Coronal image, shows branches 1st segment of the subclavian artery.

Axial image, shows branches 2nd segment of the subclavian artery.

Axial image, shows branches 3rd segment of the subclavian artery.

3dVR shows path of the vertebral artery getting close to the transverse process and into the transverse foramen (C6 level). At the level of the atlas bone it circles posteriorly and enters the foramen magnum.

Anatomic model and axial CT image: the marker show entry Point of the vertebral artery (V3) into the foramen magnum.

Internal jugular vein, common carotid artery and vagus nerve; enclosed in thecarotid sheath (green line). The sternocleidomastoid muscle is anterior to it.

Axial images, caudal to cranial planes, show variations in relative positionsbetween ICA end ECA; the pink structure represents the parotid gland

Schematic showing how CC bifurcations corresponds to superior margin ofthyroid cartilage.

Schematic showing branching of the ECA and some relevant distal subdivisions (internal maxillary artery).

3dVR red arrow shows superior thyroid artery, the inset with different color lookup tables demonstrate the relationship with the gland

Red arrows point superior laryngeal artery as it pierces the thyrohyoid Membrane (superior laryngeal nerve, not visible, travels with the artery).

MIP image shows lingual artery, relationship with greater cornu ofthe hyoid bone and then upward directed into the tongue muscles.

The images show relationship between lingual artery and lingualveins and with the muscles forming the floor of the mouth.

3dVR facial artery path is shown (thin white arrows): it ascends crossing the submandibular gland circling the lower margin of the mandible up toward the nasolabial sulcus.

Facial artery is small and more superficial than facial vein, they are separatedby the zygomatic muscle. Deeper the facial vein is crossed by the parotid duct.

The slender ascending pharyngeal artery traces a long path to the skull base.

3dVR shows (white arrow) the superficial temporal artery and the branchingin frontal an parietal divisions, better appreciated on axial images.

3dVR (white arrow) internal maxillary artery from origin to the mandibular portion then moving into the infratemporal fossa (pterygoid portion) and reaching the pterygopalatine fossa.

Internal maxillary artery 1st portion, mandibular (red arrow), runs along the lower border of the lateral pterygoid muscle.

Inferior alveolar artery, branch of the 1st portion of the internal maxillary artery. Distal part runs into the mandibular canal pairing with the mandibular vein and the mandibular nerve.

Middle meningeal artery (red arrow), branch of the 1st part of the internal maxillary artery; passes trough the spinous canal, shown on anatomic model and CT of the skull base.

Conventional neck angiography.

3D CT angiography.

3D CT angiography.

The cerebral arteries: (a) blood supply to the brain by the internal carotid artery (ICA)anteriorly, and the vertebral artery (VA) and the basilar artery (BA) posteriorly; (b) ICA and VA connected by the circle of Willis; (c) anterior cerebral artery along with the ICA, VA, and BA; (d) middle cerebral artery along with the ICA, VA, and BA; (e) posterior cerebral artery along with the ICA, VA, and BA; (f) complete arterial system

Anterior cerebral artery.

Middle cerebral artery: (a) M1, M2, M3, and M4 segments; (b) main branches of theleft hemisphere

Posterior cerebral artery.

The circle of Willis.

Vascular variants of the circle of Willis: (a) double anterior communicating artery; (b) absent left posterior communicating artery; (c) absent left P1 segment (the variants are in white)

Coronal arterial anatomy of brain sagittal arterial anatomy of brain.

Frontal projection from a right vertebral artery angiogram illustrates the posterior circulation. The vertebral arteries join to form the basilar artery. The posterior inferior cerebellar arteries (PICA) arise from the distal vertebral arteries. The anterior inferior cerebellar arteries (AICA) arise from the proximal basilar artery. The superior cerebellar arteries (SICA) arise distally from the basilar artery prior to its bifurcation into the posterior cerebral arteries.

Frontal projection from a right vertebral artery angiogram illustrates the posterior circulation. The vertebral arteries join to form the basilar artery. The posterior inferior cerebellar arteries (PICA) arise from the distal vertebral arteries. The anterior inferior cerebellar arteries (AICA) arise from the proximal basilar artery. The superior cerebellar arteries (SICA) arise distally from the basilar artery prior to its bifurcation into the posterior cerebral arteries.

Frontal view of a cerebral angiogram with selective injection of the left internal carotid artery illustrates the anterior circulation. The anterior cerebral artery consists of the A1 segment proximal to the anterior communicating artery with the A2 segment distal to it. The MCA can be divided into 4 segments: the M1 (horizontal segment) extends to the limen insulae and gives off lateral lenticulostriate branches, the M2 (insular segment), M3 (opercular branches) and M4 (distal cortical branches on the lateral hemispheric convexities).

Lateral view of a cerebral angiogram illustrates the branches of the anterior cerebral artery and Sylvian triangle. The pericallosal artery has been described to arise distal to the anterior communicating artery or distal to the origin of the callosomarginal branch of the anterior cerebral artery (ACA). The segmental anatomy of the ACA has been described as follows: the A1 segment extends from the internal carotid artery (ICA) bifurcation to the anterior communicating artery; A2 extends to the junction of the rostrum and genu of the corpus callosum; A3 extends into the bend of the genu of the corpus callosum; A4 and A5 extend posteriorly above the callosal body and superior portion of the splenium. The Sylvian triangle overlies the opercular branches of the middle cerebral artery (MCA), with the apex representing the Sylvian point.

Parcellation of the venous system: (a) dural sinuses (DS); (b) superficial veins with the DS; (c) deep veins with the DS; (d) complete venous system

Dural sinuses (the left hemisphere is labeled)

Superficial cerebral veins of the left hemisphere.

Deep cerebral veins.

Intracranial venous system anatomy of dural sinuses, cortical veins, deep intra-cerebral veins and cavernous sinus.

3dVR show deep and superficial jugular veins and their tributary.

3dVR shows superficial jugular and anterior jugular veins and their tributary vessels.

The images show position of the retromandibular vein, the facial nerve c.n. VII (not visible) is superficial to it, while the ECA is deeper.

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