Transcranial Doppler and Misc Cerebrovascular Flashcards
What is capable of evaluating onset, severity, and time course of vasoconstriction from subarachnoid hemorrhage?
transcranial Doppler
Transcranial Doppler is capable of assessing what?
Intracranial arteriovenous malformations
Assess patients with suspected brain death
Intracranial stenosis, occlusions, and assess collateral circulation
Limitations of transcranial Doppler?
- Recent eye surgery
- Adequate penetration of temporal bone from hyperostosis
- Inaccurate vessel identification with nonimaging technique
What are three acoustic windows used for transcranial doppler?
transtemporal, transorbital, and transforaminal/suboccipital
What is required for accurate vessel identification with transcranial doppler?
- Depth of sample volume
- Velocity of blood flow
- Direction of blood flow
- Relationship of flow patterns to one another
2 MHz pulsed Doppler, zero angle of insonation is assumed, and time average max velocity (TAMV) or mean velocity are used in what?
transcranial doppler
The unilateral transtemporal approach if used for what vessels?
MCA, ACA, PCA, and terminal ICA
Ipsilateral transorbital approach to evaluate what arteries?
ophthalmic artery and carotid siphon
The intracranial vertebral and basilar arteries are evaluated with what approach?
transforminal/ suboccipital approach
What is the cross-over collateral pathway?
transcranial
Antegrade flow in anterior cerebral artery from contralateral ACA via anterior communicating artery
What is the external to internal collateral pathway?
transcranial
retrograde flow in opththalmic artery
What is the posterior to anterior collateral pathway?
transcranial
increased flow in posterior cerebral artery (PCA), reversing direction of flow in the PCom artery
Factors that may alter intracranial blood flow?
age, sex, hematocrit, blood gases, metabolism
Vasospasm transcranial?
-Most accurate in MCA
-Serial recordings necessary
-Mean velocities >120 cm/s
Severe vasospasm = >200cm/s
Indication of arteriovenous malformation in transcranial doppler?
- Increased systolic and diastolic flow velocities
- Very low pulsatility indices
- Reduced flow in adjacent arteries
Subclavian occlusion results in retrograde flow in what artery?
ipsilateral vertebral
What is a recommended treatment for subclavian steal?
bypass graft or endarerectomy
Indications of subclavian steal?
- BP difference of 15-20 mmHg
- Decreased pulses in affected arm
- Ipsilateral vertebral artery feeding high-resistance vascular bed
- Patient usually asymptomatic, arm claudication is rare
Inflammation of the arterial wall of the superficial temporal artery or its frontal and/or parietal branches?
temporal arteritis
Characteristics of temporal arteritis?
- Inflammed arterial segments usually larger in diameter with homogeneous thickening evident on B-mode
- An anechoic halo from edema of the intima may be seen
- Intimal thickening may result in hemodynamically significant stenosis where PSV’s are doubled
An arteriography can be usesd to detect abnormalities such as?
filling defect, absent vessel, aberrant anatomy
Equation for calculating diameter reduction longitudinally?
DR=(1-d/D) x 100
Equation used to calculate diameter reduction in trans?
a=d^2
What test is extremely sensitive in detecting the presence of stenosis but tends to overestimate the disease process?
MR angiography
