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Diagnostic Medical Sonography Program
Vascular Technology
• Lecture: 17 Cerebrovascular Gross Anatomy
Holdorf
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
ICA continued;…
• Terminates in the middle cerebral artery
(MCA) and anterior cerebra artery (ACA)
• Distributes blood to low-resistance vascular
beds
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
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
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)
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
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 =
Velocity =
Pressure
Pressure
• Pressure gradients or areas of flow separation
are set up: can occur in a vessel because of a
geometry change, with or without intraluminal 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):
Poiseuille’s Law combined with
Resistance equation
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
Less frequent symptoms
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•
•
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Confusion
Headache
Hearing loss
Numbness
Loss of consciousness
Dysarthria : difficult or unclear speech
Tinnitus
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).
Effects of Stenosis on Flow
Characteristics
1. Velocity acceleration results because velocity
and area are inversely proportional;
acceleration causes increased energy loss
2. 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
Pre stenosis
At the stenosis
Post stenosis
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.
Homework
• Text book: Chapter 18
– Gross Anatomy, Physiology, and Fluid Dynamics
– Pages 199 – 206
• SDMS Assignments