**3. Catheter-based digital substraction angiography (DSA)—diagnostic test for intracranial arterial stenosis (ICAS)**

Catheter-based digital subtraction angiography (DSA) is the gold standard in the diagnosis of ICAS. ICAS is considered as symptomatic, if there are obvious radiological signs of acute ischemia in the supplying vascular area and if no other obvious cause (e.g., acute occlusion) is present.

**83**

*Diagnosis of Symptomatic Intracranial Atherosclerotic Disease*

estimation of degree and length of stenosis (DSA measures stenosis precisely); 3D reconstruction provides even greater detail, highlighting of collateral circulation (measure anterograde and collateral flow). Prabhakaran and coworkers suggested that DSA can identify the mechanisms of stroke in symptomatic ICAS by using surrogate imaging markers of stroke risk [12]: for the mechanism of *decreased antegrade flow*—the surrogate imaging marker of TICI (thrombolysis in cerebral infarction) flow grade; for the mechanism of *progression of stenosis*—the surrogate imaging marker of TICI (thrombolysis in cerebral infarction) flow grade; and for the mechanism of *poor collateral flow*—the surrogate imaging marker of collateral flow grade. However, being an invasive method that can generate periprocedural complications (periprocedural neurologic injury, access site injury, radiation risks, contrast risks, low availability, and great costs), DSA cannot be used in everyday routine clinical

**3.1 DSA allows an excellent visualization of intracranial arterial contour, at a** 

Monitoring the natural history of stenosis due to ICAD may be a useful method in finding new possible treatments. Long-term angiographic progress of ICAS has not received much attention before WASID trial; Bauer et al. [26] reported the progression of atherosclerotic stenoses by location, including extracranial and intracranial sites. Overall, 35.3% of intracranial sites progressed. Craig et al. [27] noted that intracranial ICA stenoses progressed in 5 of 5 patients on follow-up angiography. Akins and coworkers retrospectively reviewed records over a 7-year period to identify patients with ICAS and serial angiograms. The most common location for an ICAS of 50% or greater was the intracranial portion of the ICA (49% of lesions), followed by the MCA (20%), PCA (11%), distal VA and BA (11%), and

Angiography is an excellent method for monitoring intracranial atherosclerosis, but this method defines the vessel lumen only; the disease process leading to luminal narrowing being inferred [28]. If the patient has widespread atherosclerosis, the stenosis is usually ascribed to this. The arterial narrowing is generally caused by local atherosclerosis, but associated thrombus may also contribute. Emboli also cause luminal narrowing. In this situation, the follow-up study may show the complete resolution of the stenosis due to spontaneous clot lysis. This pattern was encountered in 3 of the 45 sites studied by Akins. He noted that there are also other pathological conditions that can cause vessel narrowing, such as vasculitis, vasospasm, or malignancies. He concluded that ICAS is dynamic

**3.2 DSA allows an excellent localization and evaluation of the degree and length** 

Angiographic measurement methods are routinely used nowadays in clinical practice to identify patients who may benefit from carotid endarterectomy [29]. Samuels affirmed that the established methods for measuring extracranial ICA stenosis are unsuitable for measuring the stenosis of a major intracranial artery because the intracranial arteries are often tortuous, have several branches, and are

If the prognosis of ICAS and the choice of therapy for these patients was clearly shown by WASID trial [2] to be based on the severity of ICAS, a repeatable method for measuring percent stenosis of the major intracranial arteries was required:

**of intracranial arterial stenosis (ICAS)**

narrowing gradually in their distal portions [29].

standard WASID criteria for grading of ICAS [29].

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

practice, in all patients [25].

ACA (9%) [28].

lesions [28].

**high resolution (microns)**

Regarding the advantages of DSA, it allows [12]: the visualization of vessel contour—at a high resolution (microns); the localization of stenosis; and the

*Diagnosis of Symptomatic Intracranial Atherosclerotic Disease DOI: http://dx.doi.org/10.5772/intechopen.90250*

*New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*

can coexist and interact in the same patient [16, 18, 20, 21].

ipsilateral in patients with 50–69% carotid stenosis [22].

of plaques with embolic potential, etc. [16, 18, 24].

**test for intracranial arterial stenosis (ICAS)**

obvious cause (e.g., acute occlusion) is present.

endovascular therapies [16, 18, 24].

**2.1 Clinical recurrence rate**

arms, respectively [16].

year of follow-up) [23].

studies are needed to identify and determine the degree and location of stenosis in this patient group [19]. Oh Young Bang and others asserted that these mechanisms

As we mentioned before, the annual recurrence rates for any ischemic stroke reported in the WASID trial were as high as 15 and 14% in the aspirin and warfarin

It has been shown that symptomatic ICAD is particularly burdened with a high clinical recurrence rate [3]. Moreover, Famakin and coworkers reported that most subsequent strokes in patients with symptomatic ICAS occurred in the same arterial territory were nonlacunar, and nearly half of them were disabling [19]. Their results were similar to the findings in NASCET, which showed that 95% of strokes were ipsilateral in patients with 70–99% carotid stenosis, and 71% of strokes were

It is also important to mention that Famakin and coworkers observed that patients with ICAS have a propensity for atherosclerotic stenosis at different sites within the intracranial circulation [19]. Supporting this idea, they reported that among the 27% of the strokes occurring outside the territory of the symptomatic intracranial artery, almost half (48%) could have been caused by previously asymptomatic or newly developed ICAS in a different vascular territory. However, in the same study, it was suggested that it is also possible that some of these strokes may have been caused by an embolus which partially recanalized leaving a residual stenosis [19]. Supporting this theory is data from another WASID analysis, which showed that asymptomatic ICAS that was present at study entry (coexistent with the symptomatic stenosis) was associated with a low rate of stroke (3.5% after 1

Identifying whether ICAS is actually the cause of the present stroke (determining whether the stenosis is symptomatic or asymptomatic), it is however still a challenge, knowing that, according to Famakin, in up to 20% of the patients with stroke and IACS, there is another cause for its occurrence (extracranial large artery stenosis, cardiac embolism, and small artery occlusion can co-exist with ICAS) [19]. Nowadays, different noninvasive imaging techniques can provide physiological data on the mechanisms associated with ICAD-linked stroke and their forms of coexistence, including markers of anterograde and collateral flow, dynamic cerebrovascular reserve, static tissue perfusion, characteristics and morphological details

All these data may improve stroke risk stratification, adding to clinical and anatomic (i.e., percent stenosis) predictors of stroke risk, developing mechanismspecific prevention and treatment strategies, and also serve in patients' selection for

**3. Catheter-based digital substraction angiography (DSA)—diagnostic** 

Catheter-based digital subtraction angiography (DSA) is the gold standard in the diagnosis of ICAS. ICAS is considered as symptomatic, if there are obvious radiological signs of acute ischemia in the supplying vascular area and if no other

Regarding the advantages of DSA, it allows [12]: the visualization of vessel contour—at a high resolution (microns); the localization of stenosis; and the

**82**

estimation of degree and length of stenosis (DSA measures stenosis precisely); 3D reconstruction provides even greater detail, highlighting of collateral circulation (measure anterograde and collateral flow). Prabhakaran and coworkers suggested that DSA can identify the mechanisms of stroke in symptomatic ICAS by using surrogate imaging markers of stroke risk [12]: for the mechanism of *decreased antegrade flow*—the surrogate imaging marker of TICI (thrombolysis in cerebral infarction) flow grade; for the mechanism of *progression of stenosis*—the surrogate imaging marker of TICI (thrombolysis in cerebral infarction) flow grade; and for the mechanism of *poor collateral flow*—the surrogate imaging marker of collateral flow grade. However, being an invasive method that can generate periprocedural complications (periprocedural neurologic injury, access site injury, radiation risks, contrast risks, low availability, and great costs), DSA cannot be used in everyday routine clinical practice, in all patients [25].

## **3.1 DSA allows an excellent visualization of intracranial arterial contour, at a high resolution (microns)**

Monitoring the natural history of stenosis due to ICAD may be a useful method in finding new possible treatments. Long-term angiographic progress of ICAS has not received much attention before WASID trial; Bauer et al. [26] reported the progression of atherosclerotic stenoses by location, including extracranial and intracranial sites. Overall, 35.3% of intracranial sites progressed. Craig et al. [27] noted that intracranial ICA stenoses progressed in 5 of 5 patients on follow-up angiography. Akins and coworkers retrospectively reviewed records over a 7-year period to identify patients with ICAS and serial angiograms. The most common location for an ICAS of 50% or greater was the intracranial portion of the ICA (49% of lesions), followed by the MCA (20%), PCA (11%), distal VA and BA (11%), and ACA (9%) [28].

Angiography is an excellent method for monitoring intracranial atherosclerosis, but this method defines the vessel lumen only; the disease process leading to luminal narrowing being inferred [28]. If the patient has widespread atherosclerosis, the stenosis is usually ascribed to this. The arterial narrowing is generally caused by local atherosclerosis, but associated thrombus may also contribute. Emboli also cause luminal narrowing. In this situation, the follow-up study may show the complete resolution of the stenosis due to spontaneous clot lysis. This pattern was encountered in 3 of the 45 sites studied by Akins. He noted that there are also other pathological conditions that can cause vessel narrowing, such as vasculitis, vasospasm, or malignancies. He concluded that ICAS is dynamic lesions [28].
