Lecture 8: Circle of Willis & TCD Flashcards
what is the most important pathway for collateral circulation to the brain?
circle of willis/willisian complex
what arteries join the circle of willis together?
anterior communicating artery
posterior communicating arteries
what arteries supply the circle of willis?
basilar & ICA
what does the circle of willis consist of?
2 ACAs, 2 MCAs, 2 PCAs
what are the pathways for collateral flow in the brain?
- contralateral hemisphere (through ACoA)
- POST –> ANT / ANT –> POST (through PCoAs)
what is the collateral pathway of blood for the contralateral hemisphere? (start at AO, end at RT MCA)
AO –> LT CCA –> LT ICA –> LT MCA –> LT ACA –> LT ACoA –> RT ACA –> RT MCA
what is the collateral pathway of blood going from POST –> ANT? (start at AO, end at RT MCA)
AO –> LT SUBCL –> LT VERT –> BASILAR A –> RT PCA –> RT PCoA –> TICA –> RT MCA
what MHz transducer is used for TCD?
1.5-2.5 MHz
name the 4 acoustic windows for TCD
- transtemporal
- transorbital
- transoccipital
- submandibular
the transtemporal approach is ___ to the zygomatic arch
cephalad
what 4 arteries can you evaluate with the transtemporal approach?
- TICA
- ACA
- MCA
- PCA
where do you place the probe for the transorbital approach for TCD?
inner canthus of closed eye
what should you do with your power button when scanning transorbital?
decrease your power
what 2 structures can be visualized with the transorbital approach?
- ophthalmic artery
- carotid siphon
where do you place the probe when scanning the transoccipital approach in TCD?
between the posterior margin of the foramen magnum & C1
what 2 structures can be visualized with the transoccipital approach?
- basilar artery
- intracranial parts of vertebral artery
what can you visualize with the submandibular approach of TCD?
petrous ICA
TCD can evaluate waveform & peak velocities. T/F?
false – it can measure waveform & MEAN velocities
what 5 factors can influence intracranial blood flow?
- age
- sex
- hematocrit
- blood gasses
- metabolic demand
