Cerebrovascular Anatomy and Disease Flashcards

In transcranial Doppler, the middle cerebral artery (MCA) is typically insonated through which window at a depth of 45-65 mm?

Answer: Transtemporal window

The transtemporal window, located above the zygomatic arch near the temporal bone, allows insonation of the MCA at depths of 45-65 mm.

A peak systolic velocity of 220 cm/s with an end-diastolic velocity of 85 cm/s in the ICA corresponds to which NASCET stenosis category per the Society of Radiologists in Ultrasound (SRU) consensus criteria?

Answer: 70-99% stenosis

Per SRU criteria, ICA PSV ≥125 cm/s with EDV ≥40 cm/s and ICA/CCA ratio >2.0 indicates 70-99% stenosis requiring closer evaluation.

Which anatomical variant describes the absence of one segment of the Circle of Willis, making a patient more vulnerable to stroke if a feeding vessel is occluded?

Answer: Aplastic or hypoplastic communicating artery

Aplasia or hypoplasia of communicating arteries (ACoA or PCoA) limits collateral flow reserve, increasing stroke risk when a major feeding vessel is compromised.

Carotid body tumors (paragangliomas) at the bifurcation characteristically displace which two vessels on duplex ultrasound?

Answer: ICA and ECA are splayed apart (lyre sign)

The 'lyre sign' describes widening of the angle between the ICA and ECA caused by a hypervascular carotid body tumor seated at the bifurcation.

Which duplex finding best distinguishes carotid plaque hemorrhage from calcified plaque?

Answer: Hemorrhagic plaque appears hypoechoic or heterogeneous without shadowing; calcified plaque shows dense shadowing

Intraplaque hemorrhage appears hypoechoic or heterogeneous on ultrasound, while calcification produces bright echoes with posterior acoustic shadowing.

The posterior inferior cerebellar artery (PICA) most commonly originates from the:

Answer: Vertebral artery

PICA typically arises from the distal intracranial vertebral artery, and its occlusion causes the lateral medullary (Wallenberg) syndrome.

During carotid duplex scanning, color aliasing within a stenotic segment indicates that the local flow velocity:

Answer: Has exceeded the Nyquist limit (PRF/2)

Color aliasing occurs when velocities exceed the Nyquist limit (half the pulse repetition frequency), causing color wrap-around and indicating high-velocity stenotic flow.