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Figure 6.23 Thrombolysis in brain ischemia (TIBI) residual flow grades. (Reprinted with permission from the Health Outcomes Institute, the Woodlands, TX.)

Figure 6.24 Different levels and residual signals with MCA mid-Mi MCA occlusion. (b)TIBI dampened flow signal in a occlusion, (a) TIBI blunted and minimal signals correlation patient with acute thrombus in M2 MCA subdivision, with early and late angiographic phases showing acute

Midline 80 mm

M2 MCA 40 mm

Thrombolysis Doppler

position

ICA bif 65 mm Mid Ml MCA 50 mm Early & Late Arterial Phases Post IA lysis

Midline 80 mm

M2 MCA 40 mm position

TIHI 3. location 1

Tlltl t, location 4 Pre-IA Ivsis

Affected dMl/pM2

Blunted Flow

Figure 6.24 Different levels and residual signals with MCA mid-Mi MCA occlusion. (b)TIBI dampened flow signal in a occlusion, (a) TIBI blunted and minimal signals correlation patient with acute thrombus in M2 MCA subdivision, with early and late angiographic phases showing acute

Affected dMl/pM2

32.4

TIBI Grade 3 Dampened signals and flow diversion

Mca Perforators

1. Blunted proximal-to-mid Ml MCA with positive etd-diastohc flow which indicates flow diversion to perforators, 2 Blunted proximal Ml MCA signal with positive end diastolic flow:

MFV ACA 'J MCA with decreased resistance toflowindicateflow diversion and possible transcortical collateral nation; 3. Noimal contralateral MCA signals.

1. Blunted proximal-to-mid Ml MCA with positive etd-diastohc flow which indicates flow diversion to perforators, 2 Blunted proximal Ml MCA signal with positive end diastolic flow:

MFV ACA 'J MCA with decreased resistance toflowindicateflow diversion and possible transcortical collateral nation; 3. Noimal contralateral MCA signals.

Figure 6.25 A common appearance of an acute proximal M1 middle cerebral artery (MCA) occlusion. Since the residual flow appears to be present up to the mid M1 MCA depths, differential diagnosis includes a subtotal stenosis.

In the case of an acute obstruction with fresh clot, the residual flow signals may change rapidly and will depend on recanalizatlon or reocdusion processes. (Reprinted with permission from Demchuk etal. [283].)

Tcd Waveform Partial Retrograde Flow

1 Absent Ml MCA. Al ACA and supraclmoid siphon signals,

2 Normal OA flow.

3. PCA > contralateral MCA signal

A. Contralateral MFV ACA > MCA; PI ACA < MCA;

5. Distal Al ACA with abnormally high velocities and low PI indicating partial anterior cross-filling

Figure 6.26 Carotid'T'-type occlusion on transcranial Doppler. (Reprinted with permission from Demchuk ef al. [283].)

1 Absent Ml MCA. Al ACA and supraclmoid siphon signals,

2 Normal OA flow.

3. PCA > contralateral MCA signal

A. Contralateral MFV ACA > MCA; PI ACA < MCA;

5. Distal Al ACA with abnormally high velocities and low PI indicating partial anterior cross-filling

Figure 6.26 Carotid'T'-type occlusion on transcranial Doppler. (Reprinted with permission from Demchuk ef al. [283].)

Transcranial Doppler Ophthalmic

Figure 6.27 Intracranial internal carotid artery occlusion (C1-C2 segments). TCD shows antegrade flow in the left OA and dampened TIBI grade 3 signals in the left TICA through the orbital window compared to contralateral side. DSA shows anterior cross-filling with early mass-effect (left image), and diminution of flow in C2 segment distal to the OA origin (right image).

ICA siphon MKV l.<R PI L > R OA ante^radi1 rev. LACA

ICA siphon MKV l.<R PI L > R OA ante^radi1 rev. LACA

Figure 6.27 Intracranial internal carotid artery occlusion (C1-C2 segments). TCD shows antegrade flow in the left OA and dampened TIBI grade 3 signals in the left TICA through the orbital window compared to contralateral side. DSA shows anterior cross-filling with early mass-effect (left image), and diminution of flow in C2 segment distal to the OA origin (right image).

Proximal Carotid Artery Location

Figure 6.28 Proximal internal carotid artery (ICA) occlusion. The most common site of a proximal ICA occlusion is its extracranial portion particularly at the level of the bulb (bottom left DSA image). If only transcranial Doppler Is performed without angiographic correlation, the location of a hemodynamically significant ICA obstruction can only be reported as proximal to the ophthalmic artery origin. Correlation with direct extracranial ultrasound imaging studies is necessary to determine the presence of an

Figure 6.28 Proximal internal carotid artery (ICA) occlusion. The most common site of a proximal ICA occlusion is its extracranial portion particularly at the level of the bulb (bottom left DSA image). If only transcranial Doppler Is performed without angiographic correlation, the location of a hemodynamically significant ICA obstruction can only be reported as proximal to the ophthalmic artery origin. Correlation with direct extracranial ultrasound imaging studies is necessary to determine the presence of an occlusion or a hemodynamically significant stenosis in the proximal ICA. 1 blunted signal in the MCA unilateral to ICA occlusion; 2 reversed ophthalmic artery (Inverted image); 3 contralateral ACA> MCA indicating collateralization of flow via anterior cross-filling; 4 unilateral P1 PCAorPComA flow (normal systolic flow acceleration, MFV PCA > MCA suggesting functional PComA or transcortical collateralization of flow).

Transcortical Arterial Flow

Figure 6.29 Basilar artery occlusion. Top left DSA image shows reversed filling of the distal basilarfrom carotid injection in a patient with right-sided hemiparesis and total NIHSS score of 11 points. Top right image shows reversed flow in the top of the basilar with response to carotid artery vibration. Bottom right DSA image shows occlusion of the proximal basilar and the left terminal vertebral artery in the presence of an artetic right VA (image not shown). Bottom middle image shows reverberating flow pattern in the left terminal VA. Bottom right graph of the circle of Willis summarizes flow findings.

complete ICA occlusion from hemodynamically significant proximal high-grade stenosis, and direct carotid examination should be employed to answer this question. TCD can help to determine an extension of the proximal ICA occlusion into the supraclinoid siphon or terminal ICA, tandem MCA/ICA lesions and the presence of collateral channels.

Secondary findings for any ICA occlusion site include:

1 collateral flow in the PComA and/or cross-filling via the AComA;

2 contralateral ICA compensatory velocity increase; and

3 possible frequent microemboli in the unilateral TICAorMCA.

With an occlusion in the basilar artery, the abnormal waveforms are found at 80-100+ mm via the trans-foraminal approach (Figure 6.29). Arbitrarily, the proximal BA is located at 80 mm, the midbasilar at 90 mm and the distal at 100+ mm depth.

Secondary findings may include; 1 a flow velocity increase in one or both VAs or PICAs indicating cerebellar collateral flow;

2 a high-resistance flow signal in one or both VAs indicating proximal BA occlusion;

3 a high-resistance flow signal at the origin of the BA indicating distal BA occlusion;

4 retrograde (low-resistance, stenotic) flow towards the probe at the top of the BA (proximal BA occlusion collateralized via PComAs);

5 functional PComAs with flow directed away from the probe via the temporal window; and

6 low distal BA velocities with top-of-the basilar occlusion.

TCD diagnosis of distal basilar occlusion or subtotal stenosis without obvious PComA or cross-cerebellar flows is particularly challenging [284,285]. CT angiography or three-dimensional contrast-enhanced transcranial Doppler or duplex imaging with color and power modes may be techniques of choice if distal basilar occlusion is suspected [284-286]. Special caution must be paid to the situation when only relatively low distal BA velocities are found without any other abnormal findings.

Figure 6.29 Basilar artery occlusion. Top left DSA image shows reversed filling of the distal basilarfrom carotid injection in a patient with right-sided hemiparesis and total NIHSS score of 11 points. Top right image shows reversed flow in the top of the basilar with response to carotid artery vibration. Bottom right DSA image shows occlusion of the proximal basilar and the left terminal vertebral artery in the presence of an artetic right VA (image not shown). Bottom middle image shows reverberating flow pattern in the left terminal VA. Bottom right graph of the circle of Willis summarizes flow findings.

What High Resistive Vertebral Artery

Figure 6.30 Terminal vertebral artery occlusion due to dissection at the skull entrance in a 22-year-old man complaining of dizziness and headache after lifting a heavy object. Top left DSA Image shows retrograde filling of the left terminal vertebral artery and posterior inferior cerebellar arteries from the right VA injection. Upper middle image shows low-resistance flow at the junction of the vertebral arteries and the proximal basilar (PMD depth range 65-85 mm), low resistance inverted spectral waveform and high resistance systolic spikes directed towards the probe in reversed left terminal VA. Top right DSA image shows tapering of the left VA flow with dissection at the skull entrance. Bottom left image shows low resistance flow in the right VA upon entering intracranial space. Bottom right image provides a close-up of a high resistance minimal flow signal in the reversed part of the left terminal VA just distal to its occluded segment at the atlas loop.

Figure 6.30 Terminal vertebral artery occlusion due to dissection at the skull entrance in a 22-year-old man complaining of dizziness and headache after lifting a heavy object. Top left DSA Image shows retrograde filling of the left terminal vertebral artery and posterior inferior cerebellar arteries from the right VA injection. Upper middle image shows low-resistance flow at the junction of the vertebral arteries and the proximal basilar (PMD depth range 65-85 mm), low resistance inverted spectral waveform and high resistance systolic spikes directed towards the probe in reversed left terminal VA. Top right DSA image shows tapering of the left VA flow with dissection at the skull entrance. Bottom left image shows low resistance flow in the right VA upon entering intracranial space. Bottom right image provides a close-up of a high resistance minimal flow signal in the reversed part of the left terminal VA just distal to its occluded segment at the atlas loop.

The diagnosis of vertebral artery (VA) occlusion is difficult to establish using TCD alone since an extracranial segmental occlusion may be present [287], The most accurate diagnosis with TCD can be made for a terminal VA occlusion [156]; however, the sensitivity of abnormal flow findings is only about 60% [283,287,288], Normal intracranial TCD examination cannot completely rule out VA occlusion, particularly with a proximal location of a segmental and collateralized VA occlusion, or hypoplasia [288], Figure 6.30 shows terminal VA occlusion. Secondary findings may include normal flow signals directed towards the probe on the side of occlusion indicating collateralization of flow from the other side and filling ofPICAs.

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Responses

  • Sarah
    What is highresistive vertebral artery?
    7 years ago
  • myrtle roper
    How is the flow in distal ica after total occlusion?
    7 years ago
  • sandra
    What transcranial artery cannot be imaged?
    6 years ago

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