Aortic Arch, Neck, and Brain Vascular Anatomy

• Aortic Arch, Neck, and Brain Vascular Anatomy Review include Arteries and Veins

Arteries

• Aortic Arch: It is a major artery where arteries that supply the heart, neck, and head come originate.
• Brachiocephalic: It bifurcates into the right subclavian artery and the right common carotid artery.
• Common Carotid (Right and Left): Supplies blood to the brain and bifurcates at the C4 level.
• Subclavian (Right and Left): The right and left vertebral arteries branch off respective subclavian arteries.
• Internal Carotids (Right and Left): Supplies blood to the cerebral hemispheres, pituitary gland, orbital structures, external nose, and anterior part of the brain. Enters the skull via the carotid canal in the petrous portion of the temporal bone and curves forward and medially. Each internal carotid artery bifurcates into anterior & middle cerebral arteries.
• External Carotids (Right and Left): Supplies blood to the anterior neck, face, scalp meninges, facial, maxillary, temporal, and occipital regions (Facial artery, Maxillary Superficial temporal, and Occipital arteries).
• Carotid Siphon: Part of the internal carotid artery just before bifurcation into the anterior cerebral and middle cerebral arteries; important area for pathology.
• Anterior Cerebral: Forebrain in the midline curves around the corpus callosum; several branches come off this artery.
• Middle Cerebral: Supplies lateral aspects of anterior circulation; courses toward the periphery & extends upward along the lateral portion of the brain, where they supply deep brain tissue.
• Vertebral (Right and Left): Arise from the subclavian arteries through the transverse processes of C6-C1 and enter the brain through the foramen magnum; supply blood to the posterior brain; both converge to form the basilar artery.
• Basilar: Rests on the Clivus portion of the sphenoid bone and bifurcates into the right and left posterior cerebral arteries.
• Posterior Cerebral (Right and Left): Supplies the posterior part of the brain and cerebellum.
• Anterior Communicating: Connects the two anterior cerebral arteries midline.
• Posterior Communicating: Branches off the internal carotid artery before bifurcation and connects to the posterior cerebral artery.

Veins

• Dural Venous Sinuses: Venous drainages found between the inner and outer layers of the dura mater.
• Superior Sagittal Sinus: Found in the superior border of the falx cerebri.
• Inferior Sagittal Sinus: Inferior margin of the falx cerebri.
• Straight Sinus: The channel formed where the falx cerebri meets the tentorium cerebelli; It continues the inferior sagittal sinus as it joins with the great cerebral vein.
• Transverse (Right and Left): or lateral sinuses are found along the lateral aspect of the tentorium cerebelli as it meets the occipital bone.
• Sigmoid Sinus: At the level of the petrous portions of the temporal bones, the transverse sinuses curl medially and inferiorly and become known as the sigmoid sinuses; they pass through the jugular foramen.
• Galen: Continues under the corpus callosum to form the internal cerebral vein.
• Occipital Sinus: The smallest of dural venous sinuses, runs along the inner surface of the occipital bone, attached to the posterior margin of the falx cerebelli.
• Confluence of Sinuses: Known as the Torcular Herophili, the intersection of the superior sagittal sinus, the straight sinus, the occipital sinus, & the two transverse sinuses. Its size varies and it is located inferior to the occipital lobes and postero-superiomedially to the cerebellum.
• Internal Jugular Vein (Right and Left): Extends from the base of the skull to the sternal end of the clavicle; drains the venous blood from the majority of the skull, brain, and superficial structures of the head and neck; drains from the sigmoid sinus.
• External Jugular Vein (Right and Left): Drains most of the outer structures of the head, including the scalp and deep portions of the face; drains into the subclavian vein
• Vertebral (Right and Left): Union of internal vertebral venous plexuses, a branch of occipital vein, veins of suboccipital and prevertebral muscles; drains the venous plexus that surrounds each vertebral artery; drains to the brachiocephalic veins; The vertebral vein leaves the sixth cervical transverse foramen and empties into the brachiocephalic vein.
• Subclavian (Right and Left): Continuation of the axillary vein, located underneath the clavicle. They connect with the jugular form the brachiocephalic veins.
• Brachiocephalic (Right and Left): Join the superior vena cava, where the blood is drained directly into the left atrium of the heart; A main tributary vein of the subclavian vein include the external jugular vein
• SVC: A large diameter vein located in the anterior right superior mediastinum; drains the brachiocephalic veins and azygos vein; Begins behind the lower border of the 1st right costal cartilage and descends vertically behind the 2nd and 3rd intercostal spaces to drain into the right atrium at the level of the 3rd costal cartilage;

Cerebral Angiogram Examination

• The performance of cerebral angiograms has declined, and it is no longer considered a primary diagnostic tool for cerebral pathology.
• Cerebral angiography and interventional procedures remain important in interventional neuroradiology, presurgical mapping, and pre cancer radiation treatment.
• Much of the diagnostic investigation of pathology of the brain is using CT & MRI, especially in identifying intracranial saccular aneurysms and carotid artery disease in the neck.
• Cerebral circulation time is 3 to 5 seconds long starting from the internal carotid artery to the jugular vein

Indications for Cerebral Angiogram

• Interventional & pre-surgical mapping
• For differential diagnosis
• To diagnose Aneurysms/Pseudoaneurysms
• Arteriovenous malformations (AVM)
• Atherosclerotic Disease
• Stenotic lesions (neck)
• Trauma: blunt & penetrating of the neck/face affecting vessels
• CVA
• Evaluation of intracranial lesions, neoplasms, gliomas, post-surgery _ Treatment of Angiofibromas, tumors, meningiomas
• Arteritis

Contraindications for Cerebral Angiogram

• CM sensitivity
• Advanced arteriosclerosis
• Extremely ill or comatose patients
• Severe hypertension
• Severe subarachnoid or intracerebral hemorrhaging

Complications for Cerebral Angiogram

• Contrast agent reactions
• Mechanical injuries: during vessel access or catheter placement (hemorrhage, arteriovenous fistula, mechanical obstruction, pseudoaneurysm, vessel lacerations, hematoma at the puncture site, and extravasation of CM).
• Physiologic complications: Stroke due to dislodged embolus or the introduction of foreign materials during the procedure
• Transient ischemic attacks (TIAs): Happens when blood flow to a part of the brain is blocked for a short time, usually a few minutes to hours, but does not cause permanent damage

Cerebral Arteriograms types

• Non-selective arteriogram
  • Uses Pig tail 5/6 french
  • 4 Vessel Flush of entire cerebral circulation and Aortic arch
• Selective arteriograms to visualize the cerebral ANTERIOR circulation
  • Common Carotid Angiogram
  • Internal Carotid Angiogram
  • External Carotid Angiogram
• Selective arteriograms to visualize the cerebral POSTERIOR circulation
  • Vertebral Arteriogram
  • Exam ends unless an occlusion e.g. an AVM is found and removed on the spot.
  • Injection rates, Guidewire & Catheter
  • Injection CM

Aortic arch and 4 Vessel Flush Angiograms

• Try to keep x-ray to be undertable when possible
  • Aortic Arch Open at 350 RPO or LAO projection (Merrill’s)
  • Aortic Arch Superimposed on Itself (Lateral projection) at RAO 350 to 450 useful to better show the bifurcation of the brachiocephalic and the origin of the left vertebral artery (done plane)
• The inferior margin of the mandible is superimposed onto the occiput so that as much of the neck as possible is exposed in the frontal image.
• Image acquisition sequence is 2 to 4 images/sec. for the arterial phase and 1 image/sec for capillary (parenchymal) & venous phases.
• Total image acquisition time is 7 to 10 secs.
• Equipment: biplane, automatic injector, DSA
• CM injection rate -22 mL/sec. total 45 mL
• Catheter: 5 French pigtail; 100 cm length
• Vessels demonstrated: Aortic Arch, Brachiocephalic, Rt. & Lt Subclavians and left vertebral

Rationale for Imaging Speeds

• Arterial Phase: Imaged at a higher frame rate (2–4 images/sec) due to the rapid blood flow in arteries and fast contrast media passage.
• Capillary Phase: If imaged at 4 images/sec instead of 1 image/sec, it would increase radiation dose unnecessarily without adding much diagnostic value since contrast moves more slowly in capillaries, a lower frame rate is sufficient to capture its distribution
• Venous Phase: Imaging speed is reduced in the venous phase because contrast media move more slowly through veins and the lower imaging speed (1 image/ sec) is enough to track venous filling while minimizing radiation exposure
• Main Risk of High Frame Rate: The main risk is an increased radiation dose to the patient and high frame rates are only used when necessary (such as in the arterial phase) to balance image quality and patient safety.
• Simultaneous biplane oblique projections may be produced

Arteriography of the Anterior Blood Supply to the Brain: Common Carotid Arteriography

• Carotid arteriograms are among the most frequently performed cerebral angiography studies.
• Occasionally, the common carotid arteries or cervical carotid arteries are injected before catheterization of the cerebral branches.
• The common carotid artery (CCA) and its bifurcation into internal and external carotid arteries are demonstrated in the PA and lateral projections.
• The area of bifurcation is studied carefully for occlusive disease.
• The right and left CCA are imaged individually

Arteriograms for Cerebral Anterior Circulation

Lateral Projection (Merrill’s)

• Center head to the vertically placed IR.
• Extend head enough to place IOML perpendicular to the horizontal.
• Adjust head to place the midsagittal plane vertically and parallel with IR.
• Adapt immobilization to the type of equipment being employed.
• Perform lateral projections of the anterior circulation with the CR to a point slightly cranial to the auricle and midway between the forehead and the occiput floor of the anterior fossa.

AP Axial Projection (Supraorbital) (Merrill’s)

• The petrous ridges will be projected just below the supraorbital margin, avoiding superimposition over the internal carotid arteries.
• Extend head enough to place IOML perpendicular to the CR.
• CR 200 caudally if AP axial (200 cephalad if PA axial) along a line passing ¾” superior to and parallel with a line extending from the supraorbital margin to a point ¾” superior to the EAM.

AP Axial Oblique Projection (Transorbital) (Merrill’s)

Overview of the aortic arch and related arteries and veins. Focus on arteries such as the brachiocephalic, common carotid, and subclavian. Also covers the internal and external carotids and their functions.