Transcranial US Eval

TCD

Uses 2MHz non-imaging probe

0 degree angle

Vessel velocity, direction and pulsatility and turbulence assessed

Time averaged maximum velocity (TAMV) most commonly used for TCD evaluation

Microbubble contrast can improve exam

TCI/TCCD

Uses 1.8-2.5MHz phased array to produce B-mode, color and Doppler images

Can offer ability to angle correct for PSV instead of TAMV

Vertebrobasilar system and Circle of Willis evaluated with PW Doppler

Eval ACA, PCA, MCA, siphon and verts and basilar

Uses 5-10mm sample gate

Use small field of view

NEVER INVERT PW

Cervical ICA

Extracranial segment that originates at the carotid bifurcation and extends to the petrous portion of the temporal bone

Evaluated on extracranial Duplex exam

Petrous ICA

Intracranial segment that courses along the petrous portion of the temporal bone

Not able to evaluate using 2D imaging, requires Doppler evaluation

Cavernous ICA

Tortuous intracranial segment that extends from the petrous portion of the circle of Willis

Distal end of the cavernous segment is called the supraclinoid segment

Ophthalmic artery is the first branch of the ICA and originates at the cavernous segment

ICA terminates when it splits to MCA and ACA

MCA

Receives majority of blood from the ICA and is a larger vessel than the ACA

Supplies most of the temporal lobe, anterolateral frontal lobe, and parietal lobe

Each MCA divided into 3 segments

• M1 (sphenoidal or horizontal segment, first portion)

• M2 (Sylvian or insular segment, located in the sylvian fissure)

• M3 (cortical segment, extends superiorly and inferiorly around the outer cerebrum and gives rise to numerous penetrating branches)

Terminal MCA connects to terminal ACA and PCA

Symptoms of MCA disease

Dysphasia, behavioral changes, severe hemiparesis in contralateral face/arms

MCA disease is related to Wernicke Aphasia -

Totally incomprehensive, unable to understand speech, speak, or follow directions

ACA

Supplies frontal lobe and parietal bones and corpus callosum

Each ACA is divided into two segments

• A1 (Located between ICA and AcoA)

• A2 (Located distal to the AcoA origin)

Symptoms of ACA disease

Loss of coordination, incontinence, severe leg hemiparesis or hemiplegia in contralateral leg, facial drooping or asymmetry

PCA

Both originate at the top of the basilar

Curve laterally, posteriorly and superiorly around the midbrain

Supply parts of midbrain, thalamus, temporal lobe, and occipital lobe

2 segments:

• P1 (located between basilar and PcoA)

• P2 (located distal to PcoA)

Vertebral arteries

Two vessels

Course from the subclavian arteries through vertebral pedicles and enter the cranium through the foramen magnum

Merge together in the cranium to form the single basilar artery

Proximal segments seen on extracranial evaluation, distal segments seen on TCI

Basilar artery

Formed at the junction of the two vertebral arteries inside the cranium

Supplies brainstem and cerebellum

Bifurcates into 2 PCA after superior cerebellar arteries branch off

Vertebrobasilar symptoms

Vertigo, ataxia, bilateral visual blurring or double vision, bilateral homonymous hemianopia, bilateral paresthesia, drop attack

Most common congenital anomaly of circle of Willis is

Absence of one or more communicating arteries

Most common location for intracranial aneurysm

Anterior communicating artery

AcoA

Single vessel that connects the two ACA branches

Potential for collateral flow between right and left anterior circulatory systems

Not normally directly evaluated in a TDC exam, but can be indirectly assessed by evaluating the flow direction of the main arteries of the Circle of Willis

PcoA

Two branches

Branches from the distal portion of the ICA before it terminates at the MCA/ACA bifurcation

Connects the PCA and MCA on each side

Potential for collateral flow

Not normally directly evaluated on TCD but can be indirectly assessed by evaluating the flow direction of the main renal arteries of the Circle of Willis

Most common indication for TDA/TCI

Assess vasospasm/vasoconstriction caused by subarachnoid hemorrhage

Most commonly occluded vessel with an acute stroke

MCA

Indications for TDC/TCI

Stroke, TIA, intracranial stenosis/occlusion, collateral flow due to occlusion, AV malformation (increased systolic and diastolic velocities), Vasospasm (increased PSV), Monitoring during procedures, microemboli detection, right to left shunt detection, patent foramen ovale, pediatric eval for sickle cell, suspected brain death

Contraindication for TCD/TCI

Recent eye surgery

Limitations of TDC/TCI

Hyperostosis - thickening of the cranial bones reduces sound penetration

Extensive time to pt and sonographer, incorrect vessel identification can be limited to position

Vasospasm can be mistaken for stenosis

Cannot evaluate the cerebral circulation for aneurysm formation

Cannot eval for aneurysm formation

Most common limitation of just TCD

Inaccurate vessel identification due to non-imaging technologist

Normal ACA/MCA velocity ratio

<1.2

Normal MCA/ICA velocity ratio

1.1-3.0

Normal basilar/vertebral velocity ratio

<2.0

Stenosis is most common in

The MCA, siphon and terminal ICA

MCA depth

30-60mm

MCA flow

Angle anteriorly and flow is anterior

MCA velocity

55 +- 12cm/s

ACA depth

60-80mm

ACA flow

Angle anteriorly, flow is away

PCA (P1 and P2) depth

60-70mm

PCA P1 flow

Angle posterior and caudal, flow is toward

PCA P1 Velocity

39 +- 10cm/s

PCA P2 flow

Angle posterior, flow is away

PCA P2 velocity

40 +- 10cm/s

Distal ICA depth

55-65mm

Distal ICA flow

Angle posterior and caudal, bi-directional flow

Distal ICA velocity

39 +- 9cm/s

Vertebral depth

60-90mm

Vertebral flow

Angle laterally, flow is away

Vertebral velocity

34 +- 8cm/s

Basilar depth

80-120mm

Basilar flow

Angle midline, flow is away

Basilar velocity

41 +- 10cm/s

Siphon depth

60-80mm

Siphon flow

Angle slightly lateral, flow can be away or bidirectional

Siphon velocity

41 +- 11cm/s

Ophthalmic depth

40-60mm

Ophthalmic flow

Angle medially, flow is toward

Ophthalmic velocity

21 +- 5cm/s

Abnormal intracranial vessel PSVs in TCI

Most common collateral pathway intracranially

AcoA

Anterior communicating artery collateral

Provides collateral flow between the right and left anterior systems for high grade ipsilateral ACA or ICA stenosis

Contralateral ACA will demonstrate high velocities

Flow reversal is the A1 segment of the ipsilateral ACA

Posterior communicating artery collateral

Provides collateral flow between the carotid and basilar arteries for ipsilateral ICA stenosis or occlusion

Increased velocity in the ipsilateral P1 segment

Decreased velocity in the ipsilateral P2 segment

ECA to ICA collateralization

Occurs with ipsilateral ICA stenosis/occlusion

Reversal of flow in the ipsilateral ophthalmic artery

Increased systolic and diastolic velocities in contralateral ophthalmic artery

• ECA > superficial temporal artery > supraorbital artery > ophthalmic artery > ICA

• ECA > superficial temporal artery > frontal artery > ophthalmic artery > ICA

• ECA > facial artery > angular artery > frontal artery > nasal artery

Peri-orbital Doppler

CW Doppler of the frontal artery (branch of ophthalmic)

Pt supine with 8-10MHz probe

Normal direction is towards probe

Compression of the infraorbital, facial and superficial temporal arteries is performed on both sides

FLOW AWAY from probe = IPSILATERAL ICA Occlusion

Determines if collaterals are being used to redirect flow

Intracranial AVM

Emerge during fetal development

Complications include subarachnoid hemorrhage, cerebral ischemia, cerebral aneurysm, brain damage or stroke

Vein of Galen defect

Wyburn-Mason syndrome - presents with unilateral vascular AVMs that involve brain, orbits and facial structures

US not normally used

Vasospasm

Vasoconstriction of intracranial arteries

Occurs within 14 days of the start of a subarachnoid hemorrhage

Flow velocities increase in MCA, ACA, and PCA

Always perform the repeat exams using the same depth as the initial eval

Treated with vasodilator

• Lindegaard ratio → >3 = mildly abnormal, >6 = severely abnormal

• Record highest velocities

Vasospasm is seen as a complication in

Pts with subarachnoid hemorrhage, usually a slow bleed

Patent foramen ovale

HITS are seen in the MCA a few seconds of injection of microbubbles

Sickle Cell anemia

Abnormally shaped RBCs produced by spleen

Can cause increased PSV in cranial vessels and increased risk for stroke

>200cm/s is abnormal for terminal ICA and MCA and indicate increased risk of stroke in children

Intraoperative monitoring

Most studies use depth of 50-55mm to eval M1

Can be performed at short intervals or continuously with a headband

Eval for microemboli from procedure

Noninvasive

TCD monitoring is used during:

Endarterectomy

Open heart surgery with bypass

ICU monitoring

Brian death - All waveforms have to and fro pattern and high increased resistance

Fistula and aneurysm

Intracranial arteriovenous malformations are most common in

Men

ICA terminates into

MCA and ACA

What vessels originate from the basilar

PCAs

The anterior communicating artery allows for

Flow between the right and left side of the circle of Willis

The posterior communicating arteries connect the

Anterior and posterior cerebral circulation systems

An acute stroke is most associated with blockage in:

MCAs

Limitations of TCD

Hyperstenosis

Incorrect vessel identification due to lack of imaging

Uncooperative pt

When evaluating the MCA from the temporal window, how do you move to assess the terminal ICA

Angle inferior

The transorbital window is typically used to eval the:

Ophthalmic artery

Which sign of laminar flow is not visualized in normal cerebral arteries

Spectral window

From the transtemporal window, the flow direction in a normal MCA should be:

Toward the transducer

What cardiac defect can be diagnosed using a TCD

Atrial septal defect