1. Diagnostic Medical Sonography Program
Vascular Technology
Lecture: 17 Cerebrovascular Gross Anatomy
Holdorf

2. Cerebrovascular Gross Anatomy
Anterior Circulation:
Common Carotid Artery (CCA)
Right CCA is a branch of the right innominate, while the left CCA is a branch off the aortic arch.
The majority of blood flows into the internal carotid
Internal carotid artery (ICA)
Originates from common carotid artery (CCA)
Travels into base of skull without branching
Intracranial branches include:
Ophthalmic artery: originates near carotid siphon, a significant curve of ICA
Posterior Communicating artery

3. ICA continued;…
Terminates in the middle cerebral artery (MCA) and anterior cerebra artery (ACA)
Distributes blood to low-resistance vascular beds

4. External Carotid Artery (ECA)
Originates from the CCA
Has eight major branches, the first branch is usually the superior thyroid artery
Distributes blood to high-resistance vascular beds

6. Posterior Circulation
Vertebral arteries
First branch off the subclavian artery
Right usually smaller than the left
Unite after entering skull to form basilar artery
Basilar artery
Formed by confluence of vertebral arteries
Divides into posterior cerebral arteries

11. Circle of Willis
A hexagonal arrangement of : Distal internal carotid (ICA), anterior cerebral arteries (ACA), joined together by the anterior communicating artery (AComm), posterior cerebral arteries (PCA) joined together by the posterior communicating arteries (Pcomm)

12. Collateral Pathways
Largest intra-arterial connection: circle of Willis
Important anastomoses include:
ECA-ICA connections via orbital and ophthalmic arteries
Occipital branch of ECA with atlantic branch of vertebral
Deep cervical and ascending cervical branches of subclavian to branches of lower vertebral artery

13. Physiology and Hemodynamics
Pressure/Flow Relationships
The Bernoulli principle: total fluid energy along a streamline of fluid flow is constant
Velocity E and Pressure E are inversely proportional:
velocity = Pressure
Velocity = Pressure

14. Poiseuille’s Law combined with Resistance equation:
Pressure gradients or areas of flow separation are set up: can occur in a vessel because of a geometry change, with or without intra-luminal disease
Poiseuille’s Law combined with Resistance equation:
Quantity of flow(Q) is related to the pressure gradient across an arterial segment (P), radius of the vessel (r), viscosity of the fluid (n), and length of the vessel (L):

15. Poiseuille’s Law combined with Resistance equation

21. Vertebrobasilar Insufficiency with Vertigo Accompanying Symptoms Common
Visual
Diplopia : double vision
Illusions
Hallucinations
Visual field deficits
Drop attacks: sudden spontaneous falls while standing or walking, with complete recovery in seconds or minutes.
Incoordination
Weakness

22. Less frequent symptoms
Confusion
Headache
Hearing loss
Numbness
Loss of consciousness
Dysarthria : difficult or unclear speech
Tinnitus

24. Amaurosis Fugax
(Latin fugax meaning fleeting, Greek amaurosis meaning darkening, dark, or obscure) is a painless transient monocular or binocular visual loss (i.e., loss of vision in one or both eyes that is not permanent).

25. Effects of Stenosis on Flow Characteristics
Velocity acceleration results because velocity and area are inversely proportional; acceleration causes increased energy loss
Blood flow must change direction as the flow stream narrows entering the stenosis and enlarges as it exits; eddy current, turbulence, and vortices cause energy loss through inertia

26. Pre stenosis At the stenosis Post stenosis

28. Additional Notes; Lecture 17 Cerebrovascular Gross Anatomy
Know your anatomy
Anterior Circulation
Posterior Circulation
The right vertebral artery is just a bit smaller (diameter wise) than the left.
Viscosity of the fluid (blood) is effected by hematocrit (the volume percentage of red blood cells in blood-normally about 45% in men and 40% in women.

29. Homework Text book: Chapter 18 SDMS Assignments
Gross Anatomy, Physiology, and Fluid Dynamics
Pages 199 – 206
SDMS Assignments