Week 2 Flashcards
Blood follows a path of?
Least resistance
What affects resistance in regards to hemodynamics?
Length and width
If blood were presented with two paths, a short and narrow one or a long and wide one, which path would it take?
The long and wide–the path of least resistance.
The most common collateral pathways involve the ______________.
Circle of Willis
What are 3 major collateral routes?
Other side of CoW
Posterior cerebral circulation
External carotid artery branches
Describe the pathway that blood can flow from the left hemisphere from the other side of the circle:
Right CCA→ rt. ICA → rt. ACA→ across the anterior communicating artery→ retrograde down the left ACA→ lt. MCA→ lt. hemisphere
Describe the alternate pathway that may originate from the posterior circulation:
Vertebral artery flow enters the basilar artery→ lt. posterior cerebral artery→ left posterior communicating artery→ distal lt. ICA→ lt. MCA
Describe the alternate pathway that may originate from the external carotid circulation:
Lt. ECA → ECA branch (superficial, temporal, maxillary or facial) → retrograde down an ICA branch (supraorbital, nasal or frontal) → continue to retrograde flow down the ophthalmic artery → carotid siphon → MCA → lt. hemisphere
What is the second most important source of collateral flow?
Anastomosis between branches of the ECA and ICA via orbital and ophthalmic arteries
What are the 6 intracranial-extracranial anastomoses?
Lacrimal Supraorbital Anterior/Posterior ethmoidal Medial Palpebral Frontal Dorsal Nasal Artery
The normal flow in the ophthalmic artery is retrograde and if there is an occlusion present, it will become antegrade flow. True or false
False
Adequate arterial perfusion relies on what? (3)
Cardiac output
Blood volume
Systemic blood pressure
If circulation is compromised, what can this lead to?
Hypoxia or anoxia
Why do collaterals develop?
Because of a change in the pressure gradient between the vessels, caused by a stenosis
If the pressure drops enough to attract flow from a vessel sitting further down the line, blood vessels may abandon their normal routes and take advantage of the new, lower pressure route. What is an example of this phenomenon?
SSS
In older individuals what can we see with their collateral pathways?
Hypoplastic or atherosclerotic
What branches of the ECA can be collaterals?
Superficial
Maxillary
Facial
Temporal
What branches of the ICA are involved in the ECA collateral circulation?
Facial
Nasal
Supraorbital
What is most essential to determine when examining the vertebrals?
Presence/absence of flow
Direction of flow
Vertebral basilar system provides 20-30% of cerebral blood flow. True or false
True
If there’s a vertebral occlusion, where is the blood flow shunted? (2)
Thyrocervical trunk
Costocervical trunk
Where do the vertebral arteries arise from?
Subclavian arteries
Basilar artery connects to the CoW via what vessel?
PCAA
What is nystagmus?
Rapid involuntary movement of the eye
Vertebral flow is low or high resistance?
Low
What is the normal velocity for the vertebrals?
20-60cm/s
Which vertebral artery is more readily seen?
Right
L=larger
R=readily seen
Which vertebral artery is commonly larger?
Left
SSS is most often seen on which side?
Left
What amount of pressure difference is there between two arms when SSS is present?
20-40mmHg
slides are either saying 20 or 40, so maybe just know both
What’s the typical PSV in the SCA when there’s a SSS?
> 400cm/s
Loss of normal triphasic waveform
One slide also said 500 so IDK
A syndrome is what?
The aggregate of signs, symptoms or other manifestations to constitute the characteristics of a morbid entity.