**4.1 TCD/TCCS can detect, localize, and grade the severity of ICAS**

In clinical practice, interpretation of TCD data should be individualized, with various parameters (velocities values, spectrum, waveform patterns, flow pulsatility, collateral flows, status of extracranial arteries, systemic conditions: anemia, etc.) (**Tables 1** and **2**) [35]. TCD presents higher precision for identification of ICAS in the MCA and BA than in other intracranial arteries, due to the tortuosity in the latter [33].

ICAS criteria are direct and indirect.


*MCA, middle cerebral artery; ACA, anterior cerebral artery; PCA, posterior cerebral artery; BA, basilar artery; VA, vertebral artery; MFV, mean flow velocity; n.a., not available; and SPR, stenotic/prestenotic MFV ratio.*

#### **Table 1.**

*TCD criteria for intracranial stenosis (ICAS) [33].*


*MCA, middle cerebral artery; ACA, anterior cerebral artery; PCA, posterior cerebral artery; BA, basilar artery; VA, vertebral artery; and PSV, peak systolic velocity.*

**87**

**Figure 2.**

**Figure 1.**

*Diagnosis of Symptomatic Intracranial Atherosclerotic Disease*

diffuse intracranial disease (**Figures 1, 2**).

*TCDS transtemporal approach, axial, midbrain plane, color mode (left C1 stenosis).*

**A.** Direct criteria (modifications observed at the stenosis level) include:

*TCDS, transtemporal approach, axial midbrain plane, color mode (left M1 higher grade stenosis).*

a.A color aliasing phenomenon (only in TCCS exam), which may indicate augmented flow velocities, caused by a stenosis or other etiologies (tortuos-

b.A progressive focal increase of blood flow velocities in ≥50% stenosis or paradoxical velocity decrease with very severe stenosis, near-occlusion or

*DOI: http://dx.doi.org/10.5772/intechopen.90250*

ity, etc.) [35].

#### **Table 2.**

*TCCS criteria for intracranial stenosis (ICAS) [42].*

**A.** Direct criteria (modifications observed at the stenosis level) include:

