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ASN CNSA practice questions

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Question 1Neurosonology (RPNI)

On a transcranial Doppler (TCD) study, which intracranial vessel is most commonly insonated through the temporal acoustic window at a depth of approximately 50 mm with flow directed toward the probe?

  1. Anterior cerebral artery
  2. Middle cerebral artery Correct answer.
  3. Basilar artery
  4. Posterior cerebral artery

Explanation

The middle cerebral artery is the most reliably insonated vessel via the transtemporal window, typically at depths of 40–65 mm with flow directed toward the transducer. The anterior cerebral artery is insonated at greater depth with flow directed away from the probe, and the posterior cerebral artery is identified through the posterior temporal window. The basilar artery is approached through the transforaminal window.

Question 2Neurosonology (RPNI)

Which parameter on TCD represents the pulsatility of the intracranial waveform and is calculated from peak systolic, end-diastolic, and mean flow velocities?

  1. Mean flow velocity
  2. Systolic/diastolic ratio
  3. Pulsatility index Correct answer.
  4. Resistive index

Explanation

The pulsatility index (Gosling index) equals (peak systolic velocity minus end-diastolic velocity) divided by mean velocity. It reflects downstream vascular resistance and waveform pulsatility. Resistive index uses the same velocity difference but divides by peak systolic velocity, and the systolic/diastolic ratio is a simple ratio rather than a pulsatility index.

Question 3Neurosonology (RPNI)

On color duplex imaging of the extracranial internal carotid artery, which feature best distinguishes the internal carotid artery from the external carotid artery near the bifurcation?

  1. The internal carotid artery is usually the more medial branch
  2. The internal carotid artery has a higher resistance waveform
  3. The internal carotid artery is usually smaller in caliber
  4. The internal carotid artery typically has no branches in the neck and a low-resistance waveform Correct answer.

Explanation

The internal carotid artery supplies the brain and therefore shows a low-resistance waveform with continuous diastolic flow, and it typically has no cervical branches. The external carotid artery has a higher-resistance waveform and gives off branches such as the superior thyroid and facial arteries. The internal carotid artery is usually posterolateral and larger.

Question 4Neurosonology (RPNI)

In a normal adult, which waveform pattern is expected in the internal carotid artery distal to the bifurcation?

  1. Monophasic with absent diastolic flow
  2. High-resistance with reversed diastolic flow
  3. Biphasic with a sharp diastolic notch
  4. Low-resistance with continuous forward diastolic flow Correct answer.

Explanation

Because the internal carotid artery supplies the low-resistance cerebral circulation, its Doppler waveform shows broad spectral broadening and continuous forward flow throughout diastole. High-resistance patterns with reduced or reversed diastolic flow are seen in external carotid branches or in abnormal states such as distal occlusion.

Question 5Neurosonology (RPNI)

What is the primary purpose of using the transforaminal (suboccipital) acoustic window during TCD?

  1. To assess the superficial temporal artery
  2. To insonate the middle cerebral artery
  3. To insonate the basilar and vertebral arteries Correct answer.
  4. To measure the ophthalmic artery velocity

Explanation

The transforaminal window at the foramen magnum allows insonation of the vertebral arteries and the basilar artery. The middle cerebral artery is accessed transtemporally, and orbital vessels are accessed transorbitally. The superficial temporal artery is an extracranial vessel assessed with standard duplex, not the transforaminal window.

Question 6Neurosonology (RPNI)

Which finding on TCD most directly indicates a hemodynamically significant stenosis of the middle cerebral artery?

  1. A focal velocity increase with post-stenotic turbulence Correct answer.
  2. Loss of the diastolic component in the external carotid artery
  3. A high-resistance waveform in the ophthalmic artery
  4. A diffuse reduction in velocity across all vessels

Explanation

A focal, segmental increase in peak systolic velocity at the site of narrowing, often with spectral broadening or turbulence downstream, is the hallmark of significant intracranial stenosis. Global velocity reduction suggests a proximal or systemic problem, and findings in other vessels do not localize to the middle cerebral artery.

Question 7Neurosonology (RPNI)

During a TCD examination, a velocity increase is detected in the right middle cerebral artery at 55 mm. What additional maneuver best helps distinguish a true stenosis from a compensatory velocity increase?

  1. Compression of the ipsilateral common carotid artery
  2. Increasing the sample volume to its maximum
  3. Changing the color map to a different scale
  4. Assessment of the contralateral middle cerebral artery and comparison of velocities Correct answer.

Explanation

Comparing the symptomatic side with the contralateral side helps identify focal, asymmetric velocity elevation consistent with stenosis rather than a symmetric compensatory increase. Carotid compression is not a routine diagnostic maneuver and carries risk. Sample volume and color scale adjustments do not resolve the physiologic question.

Question 8Neurosonology (RPNI)

A patient with a known severe internal carotid artery stenosis shows a markedly damped, low-velocity middle cerebral artery waveform with reduced pulsatility. What does this most likely reflect?

  1. Hyperdynamic cerebral circulation
  2. Increased intracranial pressure
  3. Distal embolic occlusion of a small branch
  4. Impaired proximal inflow with compensatory distal vasodilation Correct answer.

Explanation

A damped, low-velocity, low-pulsatility waveform distal to a severe stenosis reflects reduced perfusion pressure with compensatory distal vasodilation to maintain flow. Embolic branch occlusion would produce a focal deficit rather than a global damping pattern. Increased intracranial pressure typically raises pulsatility and reduces diastolic flow.

Question 9Neurosonology (RPNI)

Which TCD finding is most consistent with the diagnosis of brain death in an adult?

  1. Increased diastolic velocities with low pulsatility
  2. High-velocity flow in all intracranial vessels
  3. Continuous low-resistance flow in the middle cerebral artery
  4. Brief systolic spikes with absent diastolic flow, progressing to no detectable flow Correct answer.

Explanation

In brain death, rising intracranial pressure abolishes cerebral perfusion, producing brief systolic spikes with absent or reversed diastolic flow and eventually no detectable signal. High or continuous low-resistance flow indicates preserved perfusion, not cerebral circulatory arrest.

Question 10Neurosonology (RPNI)

On TCD, the ophthalmic artery is best insonated through which approach, and what flow direction is normally expected?

  1. Transforaminal approach with flow directed away from the probe
  2. Transorbital approach with flow directed toward the probe Correct answer.
  3. Transtemporal approach with bidirectional flow
  4. Submandibular approach with low-resistance flow

Explanation

The ophthalmic artery is insonated through the transorbital window at a shallow depth, and normal flow is directed toward the probe as blood moves from the carotid siphon toward the orbit. Flow reversal in the ophthalmic artery can indicate collateralization from the external carotid in the setting of internal carotid occlusion.

Question 11Neurosonology (RPNI)

A transcranial Doppler shows reversed flow in the ophthalmic artery in a patient with a suspected internal carotid occlusion. What does this finding most likely indicate?

  1. Increased intracranial pressure
  2. Collateral supply from the external carotid circulation Correct answer.
  3. Acute retinal artery occlusion
  4. Normal variant flow in the ophthalmic artery

Explanation

Reversed ophthalmic artery flow indicates that blood is reaching the orbit from external carotid branches and flowing retrograde toward the siphon to supply the hemisphere, a sign of proximal internal carotid occlusion with collateralization. It is not a normal variant and does not directly indicate retinal artery occlusion or raised intracranial pressure.

Question 12Neurosonology (RPNI)

Which measurement is used to grade the severity of an internal carotid artery stenosis on duplex ultrasound according to standard criteria?

  1. The diameter of the common carotid artery alone
  2. The mean velocity in the vertebral artery
  3. Peak systolic velocity at the stenosis combined with plaque morphology and post-stenotic findings Correct answer.
  4. The pulsatility index of the external carotid artery

Explanation

Stenosis severity is graded using peak systolic velocity at the narrowest point along with end-diastolic velocity, the internal carotid to common carotid velocity ratio, plaque appearance, and post-stenotic turbulence. Isolated measurements of other vessels do not grade the stenosis.

Question 13Neurosonology (RPNI)

Which spectral Doppler feature is characteristic of a hemodynamically significant carotid stenosis at the site of narrowing?

  1. Focal elevation of peak systolic velocity with spectral broadening Correct answer.
  2. Spectral broadening with low peak systolic velocity
  3. Absent flow throughout the cardiac cycle
  4. Reversed flow with a high-resistance waveform

Explanation

At a significant stenosis, velocity increases focally because of the reduced lumen, and spectral broadening occurs from disturbed, non-laminar flow. Low velocity with broadening suggests a different process, and absent or reversed flow suggests occlusion or a very severe lesion with different hemodynamics.

Question 14Neurosonology (RPNI)

What does a high pulsatility index in the middle cerebral artery most likely suggest?

  1. Normal autoregulation
  2. Decreased distal cerebrovascular resistance
  3. A proximal high-grade stenosis
  4. Increased distal cerebrovascular resistance Correct answer.

Explanation

Pulsatility index rises when distal resistance increases, reducing diastolic flow relative to systolic flow. Decreased distal resistance lowers the index. A proximal stenosis typically produces a damped, low-pulsatility waveform rather than a high pulsatility index.

Question 15Neurosonology (RPNI)

During a TCD study, the technologist identifies a vessel at 65 mm depth through the temporal window with flow directed away from the probe. Which vessel is most likely being insonated?

  1. Middle cerebral artery
  2. Posterior cerebral artery
  3. Anterior cerebral artery Correct answer.
  4. Internal carotid artery siphon

Explanation

The anterior cerebral artery is typically identified at 60–75 mm depth through the temporal window with flow directed away from the probe. The middle cerebral artery at similar depth shows flow toward the probe, and the posterior cerebral artery is accessed through the posterior temporal window.

Question 16Neurosonology (RPNI)

Which finding on TCD suggests a vasospasm in the middle cerebral artery after subarachnoid hemorrhage?

  1. Reduced velocity with increased pulsatility
  2. Reversed systolic flow
  3. Focal or diffuse velocity elevation with a high mean flow velocity Correct answer.
  4. Absent diastolic flow

Explanation

Vasospasm narrows the arterial lumen and produces elevated mean and peak systolic velocities, often with a high Lindegaard ratio when compared with extracranial flow. Reduced velocity and increased pulsatility suggest a different process, and absent diastolic flow suggests severe distal obstruction.

Question 17Neurosonology (RPNI)

The Lindegaard ratio compares which two measurements to distinguish vasospasm from hyperemia?

  1. Ophthalmic to middle cerebral artery velocity
  2. Systolic to diastolic velocity in the middle cerebral artery
  3. Vertebral to basilar velocity
  4. Intracranial middle cerebral artery velocity to extracranial internal carotid velocity Correct answer.

Explanation

The Lindegaard ratio is the mean middle cerebral artery velocity divided by the mean extracranial internal carotid velocity. A ratio above roughly 3 supports vasospasm, while a lower ratio with high velocities suggests hyperemia. The other ratios do not serve this purpose.

Question 18Neurosonology (RPNI)

A patient with a suspected vertebrobasilar insufficiency undergoes TCD. Which finding would most support the diagnosis?

  1. Reduced basilar artery velocity with a damped waveform Correct answer.
  2. High-resistance flow in the external carotid artery
  3. Absent diastolic flow in the middle cerebral artery
  4. Increased basilar artery velocities with a normal waveform

Explanation

Reduced velocity with a damped waveform in the basilar artery suggests impaired inflow from proximal vertebral or subclavian disease. Increased velocities would suggest stenosis or vasospasm rather than insufficiency, and findings in other vessels do not localize to the posterior circulation.

Question 19Neurosonology (RPNI)

What does a subclavian steal phenomenon demonstrate on vertebral artery Doppler during arm exercise or cuff inflation?

  1. Increased antegrade vertebral flow on the affected side
  2. Bidirectional flow in the basilar artery only
  3. Reversed vertebral artery flow on the affected side Correct answer.
  4. Absent flow in the contralateral vertebral artery

Explanation

In subclavian steal, a proximal subclavian stenosis causes blood to flow retrograde down the ipsilateral vertebral artery to supply the arm, and this reversal may be provoked or exaggerated by arm exercise or cuff inflation. Antegrade increase would be the normal response, and the other findings do not define the steal.

Question 20Neurosonology (RPNI)

Which factor most limits the accuracy of TCD for detecting intracranial stenosis in a patient with a thick skull?

  1. Excessive color gain
  2. Inadequate acoustic window penetration Correct answer.
  3. High pulse repetition frequency
  4. Use of a 2 MHz probe

Explanation

Temporal bone thickness can attenuate the ultrasound beam and prevent adequate insonation, limiting the study. Gain settings and pulse repetition frequency are adjustable technical parameters, and a 2 MHz probe is the standard transducer for TCD.

Question 21Neurosonology (RPNI)

On duplex ultrasound, which plaque characteristic is most associated with an increased risk of embolic stroke?

  1. A hypoechoic plaque with an irregular surface Correct answer.
  2. A uniformly echogenic, smooth plaque
  3. A thin, regular fibrous cap
  4. A calcified plaque with acoustic shadowing

Explanation

Hypoechoic, irregular plaques are more likely to be lipid-rich and unstable, increasing embolic risk. Uniformly echogenic, smooth, heavily calcified, or thin-capped regular plaques are generally associated with lower embolic risk in this context.

Question 22Neurosonology (RPNI)

A TCD examination reveals a high-velocity middle cerebral artery signal with a Lindegaard ratio of 1.8 in a patient with a recent subarachnoid hemorrhage. How should this be interpreted?

  1. Findings indicate brain death
  2. Findings are diagnostic of severe vasospasm
  3. Findings indicate a proximal carotid occlusion
  4. Findings are consistent with hyperemia rather than vasospasm Correct answer.

Explanation

A Lindegaard ratio below approximately 2–3 with elevated velocities favors hyperemia, because the extracranial internal carotid velocity is also elevated. Vasospasm typically produces a ratio above 3. Carotid occlusion and brain death produce very different waveform patterns.

Question 23Neurosonology (RPNI)

In a patient with a severe internal carotid artery stenosis, which combination of TCD findings best indicates exhausted cerebral autoregulation?

  1. Elevated pulsatility index with normal velocities
  2. Symmetric velocities in both middle cerebral arteries
  3. Reduced pulsatility index with blunted response to carbon dioxide challenge Correct answer.
  4. Increased diastolic velocity with low resistance

Explanation

When autoregulation is exhausted, the distal vascular bed is maximally dilated, producing a low pulsatility index and loss of normal vasoreactivity to carbon dioxide. Elevated pulsatility or symmetric normal velocities do not indicate exhausted reserve.

Question 24Neurosonology (RPNI)

Which technical factor most affects the accuracy of velocity measurements when performing TCD through a temporal window?

  1. The sweep speed of the spectral display
  2. The color map selected for display
  3. The angle of insonation relative to the vessel course Correct answer.
  4. The use of a standoff pad

Explanation

Doppler velocity measurements depend on the cosine of the angle between the ultrasound beam and blood flow; an unfavorable angle underestimates true velocity. Color map choice and sweep speed affect display only, and standoff pads are not used for TCD.

Question 25Neurosonology (RPNI)

A patient with a known middle cerebral artery stenosis shows a focal velocity increase, but the contralateral middle cerebral artery shows a similar velocity increase. What is the most appropriate interpretation?

  1. Bilateral stenosis is likely, requiring further evaluation Correct answer.
  2. The finding indicates hyperemia only
  3. The finding excludes any stenosis
  4. The finding represents a normal variant

Explanation

Symmetric focal velocity elevations in both middle cerebral arteries raise the possibility of bilateral stenosis or a systemic cause and warrant further evaluation such as imaging correlation. A normal variant would not produce focal, symmetric elevation, and hyperemia would typically not be focal.

Question 26Neurosonology (RPNI)

Which vessel is most commonly used as the initial landmark for identifying the intracranial arteries through the temporal acoustic window?

  1. The internal carotid artery siphon at 75 mm depth
  2. The posterior cerebral artery at 65 mm depth
  3. The middle cerebral artery at 50-60 mm depth Correct answer.
  4. The anterior cerebral artery at 70 mm depth

Explanation

The middle cerebral artery is normally the first major vessel identified through the temporal window because it lies at a relatively consistent depth of about 50-60 mm and courses toward the probe. It then serves as the anchor for locating the anterior and posterior cerebral arteries by depth and flow direction.

Question 27Neurosonology (RPNI)

What is the normal direction of flow in the middle cerebral artery when insonated through the temporal window?

  1. Bidirectional with equal components
  2. Alternating with the cardiac cycle
  3. Toward the transducer Correct answer.
  4. Away from the transducer

Explanation

The MCA courses laterally and anteriorly toward the temporal window, so its normal Doppler signal is directed toward the transducer and appears above the baseline. This expected direction helps distinguish the MCA from the anterior and posterior cerebral arteries.

Question 28Neurosonology (RPNI)

Which transcranial Doppler parameter is defined as the difference between peak systolic and end-diastolic velocities divided by the mean velocity?

  1. Mean flow velocity
  2. Systolic-to-diastolic ratio
  3. Resistive index
  4. Pulsatility index Correct answer.

Explanation

The pulsatility index (Gosling index) is calculated as (peak systolic velocity minus end-diastolic velocity) divided by mean velocity. It reflects downstream vascular resistance and the shape of the waveform.

Question 29Neurosonology (RPNI)

Which acoustic window is used to insonate the basilar artery?

  1. Submandibular window below the mandible
  2. Temporal window above the zygomatic arch
  3. Transforaminal window at the foramen magnum Correct answer.
  4. Transorbital window through the closed eyelid

Explanation

The basilar artery is approached through the transforaminal (suboccipital) window by placing the probe at the foramen magnum and angling toward the brainstem. Flow in the basilar artery is typically directed away from the transducer.

Question 30Neurosonology (RPNI)

What does the resistive index of an intracranial artery primarily reflect?

  1. Blood oxygen saturation
  2. Upstream stenosis severity
  3. Downstream vascular resistance Correct answer.
  4. Vessel wall thickness

Explanation

The resistive index summarizes the shape of the Doppler waveform and correlates with resistance in the distal vascular bed. Higher values indicate greater downstream resistance, while lower values suggest reduced resistance.

Question 31Neurosonology (RPNI)

Which artery is insonated through the transorbital window with flow normally directed toward the transducer?

  1. Middle cerebral artery
  2. Ophthalmic artery Correct answer.
  3. Basilar artery
  4. Posterior cerebral artery

Explanation

The ophthalmic artery is insonated through the transorbital window and normally shows flow toward the transducer as blood moves anteriorly toward the orbit. This normal direction is important when assessing collateral flow in carotid disease.

Question 32Neurosonology (RPNI)

Which color Doppler artifact appears as a false reversal of flow when the velocity exceeds the Nyquist limit?

  1. Blooming artifact
  2. Twinkling artifact
  3. Mirror image artifact
  4. Aliasing Correct answer.

Explanation

Aliasing occurs when blood velocity exceeds the Nyquist limit, causing the displayed color or spectral signal to wrap to the opposite side of the scale. Adjusting the scale, baseline, or transducer frequency can correct it.

Question 33Neurosonology (RPNI)

What is the typical normal mean flow velocity range in the middle cerebral artery of a healthy adult?

  1. 40-60 cm/s Correct answer.
  2. 150-200 cm/s
  3. 10-25 cm/s
  4. 100-140 cm/s

Explanation

Normal MCA mean flow velocities generally fall around 40-60 cm/s, with some age-related variation. Velocities substantially above this range raise concern for stenosis or vasospasm.

Question 34Neurosonology (RPNI)

A technologist cannot obtain a temporal window signal despite repositioning and adjusting depth and gain. Which alternative approach can be used to insonate the middle cerebral artery?

  1. Submandibular approach along the jaw
  2. Transforaminal approach at the foramen magnum
  3. Transorbital approach through the orbit Correct answer.
  4. No alternative approach exists for the MCA

Explanation

When the temporal window is inadequate, the transorbital approach can sometimes be used to reach the intracranial circulation, including the distal MCA and carotid siphon, with reduced power settings. The submandibular and transforaminal windows do not access the MCA.

Question 35Neurosonology (RPNI)

A patient has an elevated middle cerebral artery velocity with a normal Lindegaard ratio. What is the most likely explanation?

  1. Hyperemia from increased metabolic demand Correct answer.
  2. Vasospasm after subarachnoid hemorrhage
  3. Focal atherosclerotic stenosis
  4. Cerebral circulatory arrest

Explanation

A normal Lindegaard ratio with elevated MCA velocity indicates that the velocity increase is proportional to systemic flow, consistent with hyperemia. Vasospasm would produce an elevated ratio because the extracranial velocity remains normal while the intracranial velocity rises.

Question 36Neurosonology (RPNI)

Which finding on transcranial Doppler is most consistent with a proximal internal carotid artery occlusion in the territory of the ophthalmic artery?

  1. Reversed ophthalmic artery flow toward the transducer Correct answer.
  2. Absent ophthalmic artery signal with normal MCA velocity
  3. Increased ophthalmic artery velocity with normal direction
  4. Bidirectional ophthalmic flow with a normal spectral waveform

Explanation

When the internal carotid artery is occluded, collateral flow through the external carotid branches can reverse ophthalmic artery flow so that it moves toward the transducer. This reversed direction is a classic indirect sign of proximal carotid occlusion.

Question 37Neurosonology (RPNI)

Which parameter should be adjusted to reduce aliasing when insonating a high-velocity middle cerebral artery?

  1. Increase the sample volume
  2. Increase the velocity scale Correct answer.
  3. Decrease the wall filter
  4. Increase the color gain

Explanation

Raising the velocity scale increases the Nyquist limit so that high velocities are displayed without wrapping. Increasing sample volume or color gain would not correct aliasing and could worsen the display.

Question 38Neurosonology (RPNI)

A patient with sickle cell disease undergoes transcranial Doppler screening. Which velocity threshold in the middle cerebral artery is typically used to identify high stroke risk?

  1. 50 cm/s or greater
  2. 120 cm/s or greater
  3. 80 cm/s or greater
  4. 200 cm/s or greater Correct answer.

Explanation

In sickle cell disease, a time-averaged mean velocity of 200 cm/s or greater in the MCA is associated with a substantially increased stroke risk and prompts consideration of transfusion therapy. Lower thresholds are used for conditional risk categories.

Question 39Neurosonology (RPNI)

Which waveform pattern in the middle cerebral artery suggests increased intracranial pressure?

  1. Continuous forward flow with a broad spectral envelope
  2. Increased velocity with a narrowed spectral window
  3. Low-resistance waveform with increased diastolic flow
  4. High-resistance waveform with reduced diastolic flow Correct answer.

Explanation

As intracranial pressure rises, distal resistance increases and diastolic flow diminishes, producing a high-resistance waveform with a reduced or absent diastolic component. Progression can lead to diastolic flow reversal and then to systolic spikes.

Question 40Neurosonology (RPNI)

What is the primary purpose of using the Lindegaard ratio in transcranial Doppler?

  1. To grade carotid stenosis severity
  2. To distinguish vasospasm from hyperemia Correct answer.
  3. To determine the direction of collateral flow
  4. To estimate intracranial pressure

Explanation

The Lindegaard ratio compares intracranial MCA velocity with extracranial internal carotid velocity to separate true vasospasm from a generalized increase in flow. A high ratio supports vasospasm, while a normal ratio supports hyperemia.

Question 41Neurosonology (RPNI)

Which vessel is typically insonated at a depth of 60-70 mm through the temporal window with flow directed away from the transducer?

  1. Anterior cerebral artery Correct answer.
  2. Posterior cerebral artery
  3. Basilar artery
  4. Middle cerebral artery

Explanation

The anterior cerebral artery is typically found at a slightly greater depth than the MCA and shows flow away from the transducer as it courses anteriorly and medially. Identifying this direction helps confirm the vessel identity.

Question 42Neurosonology (RPNI)

A patient with a severe middle cerebral artery stenosis shows a focal velocity increase. What additional finding at the site of stenosis supports the diagnosis?

  1. Absence of any detectable signal
  2. Spectral broadening and turbulence distal to the narrowing Correct answer.
  3. A normal waveform with a clean spectral window
  4. Reduced velocity at the site of narrowing

Explanation

At a hemodynamically significant stenosis, the velocity jet is accompanied by spectral broadening and turbulence caused by disturbed flow. These features, together with a focal velocity increase, support the diagnosis.

Question 43Neurosonology (RPNI)

Which factor most directly affects the accuracy of depth measurement during transcranial Doppler?

  1. The assumed speed of sound in tissue Correct answer.
  2. The heart rate
  3. The patient's blood pressure
  4. The angle of the probe relative to the vessel

Explanation

Depth is calculated from the round-trip time of the ultrasound pulse using an assumed speed of sound in tissue, typically 1540 m/s. If the actual tissue speed differs, the displayed depth will be inaccurate.

Question 44Neurosonology (RPNI)

A patient presents with a sudden severe headache, and transcranial Doppler shows an MCA velocity of 180 cm/s with a Lindegaard ratio of 4. What is the most likely diagnosis?

  1. Hyperemia from anemia
  2. Vasospasm after subarachnoid hemorrhage Correct answer.
  3. Carotid occlusion
  4. Normal variant

Explanation

A markedly elevated MCA velocity combined with a high Lindegaard ratio indicates true vasospasm rather than hyperemia. In the setting of sudden severe headache, this pattern is consistent with vasospasm after subarachnoid hemorrhage.

Question 45Neurosonology (RPNI)

Which finding on transcranial Doppler indicates the presence of a patent foramen ovale during a bubble study?

  1. Microembolic signals in the middle cerebral artery after agitated saline injection Correct answer.
  2. A sudden decrease in MCA velocity
  3. Reversal of ophthalmic artery flow
  4. Increased pulsatility index in the MCA

Explanation

During a bubble study, agitated saline is injected and the MCA is monitored for microembolic signals. Appearance of these signals indicates right-to-left shunting, such as through a patent foramen ovale.

Question 46Neurosonology (RPNI)

What does an absent diastolic flow component in the middle cerebral artery most likely indicate?

  1. Increased vessel diameter
  2. Elevated distal vascular resistance Correct answer.
  3. Normal flow pattern
  4. Decreased distal vascular resistance

Explanation

Loss of diastolic flow indicates high resistance in the distal vascular bed, often from elevated intracranial pressure or severe downstream disease. The waveform becomes increasingly pulsatile as diastolic flow diminishes.

Question 47Neurosonology (RPNI)

A patient with a known severe internal carotid artery stenosis has a damped MCA waveform with reduced velocity. Which additional finding would best indicate that collateral flow is inadequate?

  1. Reversal of ophthalmic artery flow
  2. Increased MCA velocity with a normal waveform
  3. Further reduction in MCA velocity with a prolonged systolic acceleration time Correct answer.
  4. Presence of microembolic signals

Explanation

A damped waveform with prolonged systolic acceleration time and further velocity reduction suggests that collateral supply is insufficient to maintain normal perfusion. This pattern indicates hemodynamic compromise distal to the stenosis.

Question 48Neurosonology (RPNI)

Which technical factor most limits the ability to obtain reliable transcranial Doppler velocities in older adults?

  1. Increased cardiac output
  2. Enlargement of the middle cerebral artery
  3. Decreased blood viscosity
  4. Thickening of the temporal bone with age Correct answer.

Explanation

Age-related thickening of the temporal bone attenuates ultrasound transmission and can make the temporal window inadequate. This is a major cause of failure to obtain reliable intracranial signals in older patients.

Question 49Neurosonology (RPNI)

A patient with a suspected brain death evaluation shows systolic spikes with no diastolic flow in the MCA. What does this pattern most likely represent?

  1. Vasospasm
  2. Normal flow with high resistance
  3. Cessation of effective cerebral perfusion Correct answer.
  4. Hyperemia

Explanation

Systolic spikes with absent diastolic flow reflect severely increased intracranial pressure that exceeds diastolic perfusion pressure, indicating ineffective cerebral perfusion. This pattern is consistent with the progression toward cerebral circulatory arrest.

Question 50Neurosonology (RPNI)

Which combination of findings best supports a diagnosis of vertebrobasilar insufficiency on transcranial Doppler?

  1. Elevated basilar artery velocity with a normal waveform
  2. Reversed ophthalmic artery flow
  3. Reduced basilar artery velocity with a damped waveform Correct answer.
  4. Absent temporal window with normal MCA velocities

Explanation

Vertebrobasilar insufficiency often produces reduced basilar artery velocity with a damped, low-resistance waveform reflecting compromised inflow. These findings, interpreted alongside clinical symptoms, support the diagnosis.