Cerebrovascular Anatomy and Disease Flashcards

A 68-year-old male presents with episodes of dizziness, vertigo, and bilateral visual disturbances. A carotid duplex ultrasound reveals antegrade flow in both internal carotid arteries and the right vertebral artery. However, the left vertebral artery demonstrates sustained retrograde flow. What is the most likely diagnosis?

Answer: Left subclavian steal syndrome

Subclavian steal syndrome is characterized by the reversal of blood flow in the vertebral artery on the same side as a significant stenosis or occlusion of the proximal subclavian artery. The retrograde flow in the left vertebral artery indicates that blood is being 'stolen' from the posterior circulation to supply the left arm, which is diagnostic of left subclavian steal syndrome.

Which of the following is the first major branch of the internal carotid artery (ICA) after it enters the cranial cavity?

Answer: Ophthalmic artery

The ophthalmic artery is typically the first major branch arising from the supraclinoid segment of the internal carotid artery after it passes through the cavernous sinus and enters the cranial cavity. It supplies blood to the structures of the orbit.

A vascular technologist is performing a Transcranial Doppler (TCD) examination through the transtemporal window. To identify the middle cerebral artery (MCA), what is the expected direction of blood flow relative to the transducer?

Answer: Antegrade (towards the transducer)

When insonating through the transtemporal window for a TCD exam, the ultrasound beam is typically aimed superiorly and slightly anteriorly. The middle cerebral artery (MCA) courses laterally from the circle of Willis, so its blood flow is directed towards the transducer, resulting in an antegrade or positive Doppler shift.

According to the widely accepted SRU (Society of Radiologists in Ultrasound) consensus criteria for grading internal carotid artery stenosis, which of the following findings is most consistent with a stenosis of 70% or greater?

Answer: Peak Systolic Velocity (PSV) greater than 230 cm/s

The SRU consensus criteria use a Peak Systolic Velocity (PSV) of greater than 230 cm/s as a primary parameter to diagnose an internal carotid artery stenosis of 70% or greater, up to near occlusion. Additional parameters like an End-Diastolic Velocity (EDV) >100 cm/s and an ICA/CCA PSV ratio >4.0 are also used to confirm high-grade stenosis.

A patient is referred for a cerebrovascular ultrasound due to symptoms of vertebrobasilar insufficiency (VBI). Which of the following symptoms is LEAST likely to be associated with this condition?

Answer: Unilateral facial droop

Vertebrobasilar insufficiency results from reduced blood flow to the posterior circulation of the brain. Symptoms typically involve structures supplied by the vertebral and basilar arteries, such as the cerebellum and brainstem, leading to vertigo, vision changes, and coordination issues. A unilateral facial droop is a classic symptom of anterior circulation stroke, often involving the middle cerebral artery territory, not typically isolated in VBI.

What is the primary purpose of the Circle of Willis in the cerebrovascular system?

Answer: To provide a collateral pathway for cerebral perfusion

The Circle of Willis is an arterial anastomosis at the base of the brain that connects the anterior (internal carotid arteries) and posterior (vertebrobasilar system) circulations. Its primary function is to provide redundancy and collateral blood flow, which can help maintain cerebral perfusion if a major contributing artery becomes stenosed or occluded.