Use of transcranial Doppler ultrasound includes detection of site/degree of stenosis/occlusion of cerebral vasculature, assessment of recanalization following occlusion (with/without thrombolytic treatment), and assessment of collateral flow in intracranial vasculature in cases of critical carotid artery stenosis (extracranial) [8].
Our main aim in this study is to assess collateral circulation in significant carotid stenosis with intracranial stenotic vessels by using transcranial color-coded duplex to determine whether they are worse or not than collaterals in cases of internal carotid stenosis alone, and consequently if the prognosis of those patients is worse or not. Collateral flow patterns are important risk factors for brain ischemia in the presence of internal carotid artery (ICA) stenosis or occlusion. So, contralateral anterior cerebral artery flow and ophthalmic artery (OA) flow reversal are studied by transcranial Doppler sonography, as they are important markers for high-grade ICA stenosis or occlusion and in detection of prognosis [9].
Our study is considered pioneer in comparing hemodynamics in cerebral collaterals between these two groups of patients, but results revealed that there is no difference statistically between them, may be due to small sample size. Our study shows that in 15 patients with significant extracranial stenosis, 3 (20%) of them obtained reversed flow in the ophthalmic artery and 3 patients of them (20%) showed change of flow in ACA (showing that contralateral ACA was the donor artery) whereas the other 15 patients of both extracranial and intracranial stenosis did not show any reversed blood flow in their ophthalmic arteries or any reversed blood flow in their ACAs; however, this was statistically not significant probably due to small sample size. These findings were somewhat different from the study done by Yueh-Feng Sung and his coworkers [10]; they assessed the clinical implications of reversed ophthalmic artery flow (ROAF) for stroke risk and outcomes in subjects with unilateral severe cervical carotid stenosis/occlusion. They investigated 128 subjects (101 with acute stroke and 27 without), selected from a large hospital patients base (n = 14,701), identified with unilateral high-grade cervical carotid stenosis/occlusion by using duplex ultrasonography and brain magnetic resonance imaging. All clinical characteristics were compared for stroke risk between acute stroke and nonstroke groups. Patients with acute stroke were divided into four subgroups according to ophthalmic artery flow direction and intracranial stenosis severity, and stroke outcomes were evaluated. The acute stroke group had significantly higher percentages of ROAF (52.5%, p = 0.003), carotid occlusion (33.7%, p = 0.046), and severe intracranial stenosis (74.3%, p < 0.001). However, multivariate analysis demonstrated that intracranial stenosis was the only significant risk factor (odds ratio = 10.38; 95% confidence interval = 3.64–29.65; p < 0.001). Analysis of functional outcomes among the four subgroups of patients with stroke showed significant trends (p = 0.018 to 0.001) for better stroke outcomes from ROAF and mild or no intracranial stenosis. ROAF improved 10–20% stroke outcomes, as compared to forward ophthalmic artery flow, among the patients with stroke and the same degree of severities of intracranial stenosis. So, this study stated that the patients with acute stroke and severe unilateral cervical carotid stenosis/occlusion significantly have high incidence of intracranial stenosis and reversal of flow in the ophthalmic artery.
In our study, the residual deficit regarding the two groups was compared and we found that those 15 patients with only extracranial stenosis were better with less NIH than those with combined intracranial and extracranial stenosis. Furthermore, we also found that prognosis of patients with only extracranial stenosis after 3 months was better than that of patients with both extracranial and intracranial stenosis. This was found also in a study done by Tsai and his colleagues [5], who stated that patients with unilateral high-grade cervical carotid stenosis/occlusion in combination with intracranial stenosis appear to be a significant risk factor for poor functional outcome. In comparison to the previous studies, our study is considered pioneer in comparing hemodynamics in cerebral collaterals between these two groups of patients, but results revealed that there is no difference statistically between them, may be due to small sample size.
However, some limitations could be noted in this study as we did not take a third group to study cerebral hemodynamics in intracranial stenosis alone in order to compare them with the cerebral hemodynamics found in the two groups already taken in this study. Also, the number of candidates studied was considered limited which may be the cause of some nonsignificant results.