Prognosis of ischemic stroke patients with or without collateralization after carotid stenosis

The objective of this study was to see the  association of the prognosis of ischemic stroke patients with or without collateralization after carotid stenosis. This study was conducted on 36 patients presenting with acute ischemic stroke who were going through digital subtraction angiography from March 2017 to March 2018. Collateralization status after unilateral or bilateral stenosis was evaluated. Modified ranking scale (mRS) score was  measured on the first day of the stroke and after three months. The disability of ischemic stroke patients was compared between patients who developed collateralization and who had not. Among them, 61.6% developed collateralization. Among the patients who developed collateralization after three months, 90.9% patients had mRS scale of ≤2 and who not developed collateralization, 85.7% patients had mRS scale of ≤2. In both the groups, the p value was <0.05. It can be concluded that carotid stenosed patients who suffered from ischemic stroke, most of the patients disability improved to some extents whether collateralization developed or not among the major vessels.


Introduction
The cerebral blood flow is supplied through the left and right internal carotid artery and basilar artery to the arterial circle of Willis, and thence to the brain.The collateral potential of the circle of Willis is believed to be dependent on the presence and size of its component vessels. 1 If internal carotid artery in one side is stenosed, the circle of Willis may allow the supply of blood from the contralateral carotid artery or the basilar artery to the territory of the stenotic internal carotid artery. 2 Impaired blood supply to the brain due to internal carotid artery obstructive disease is compensated by redistributing blood through the components of the arterial circle to maintain hemispheric circulation through the arteries emanating from the circle.The potential to develop these anterior and posterior collateral pathways depends on the continuity of the anterior and posterolateral parts of the circle of Willis, respectively.Collateral flow via the circle of Willis can be provided anteriorly via the right and left precommunicating anterior cerebral arteries (A1 segment) and the anterior communicating artery, and posteriorly via the ipsilateral posterior communicating artery and precommunicating posterior cerebral artery (P1 segment).
The size and patency of the arteries of the circle of Willis are variable. 3Substantial individual differences in the anatomy of the circle of Willis of healthy subjects have been described. 4Carotid atherosclerosis is a prominent cause of stroke in various populations around the world and noted as the most common vascular lesion in stroke patients. 5,6 er stroke, the survival of carotid stenosis patient depends on the quality of residual collateral blood supply. 7Carotid atherosclerosis may incite downstream ischemia in a specific arterial territory due to hypoperfusion, in situ thrombosis, artery to artery emboli, perforator vessel occlusion by the atherosclerotic plaque, or combined mechanisms. 8Collateral circulation may be beneficial by different pathophysiologic mechanisms, by sustaining downstream perfusion or enhancing embolic washout in distal arteries, although such influence may be diminished in perforator occlusion. 9, 10Predictors of stroke in this condition may also be explained by perfusion and the role of collaterals.Angiographic details such as the relative length and exact percentage of luminal stenosis may impact distal flow and therefore be related to collateral status.Systemic blood pressure may be related to collateralization or arteriogenesis and may also be linked with perfusion of the vascular territory. 11Even when the recurrent stroke occurs, collateral status may influence the resultant infarct size and clinical severity. 12chemic stroke outcome varies considerably,

Abstract
The objective of this study was to see the association of the prognosis of ischemic stroke patients with or without collateralization after carotid stenosis.This study was conducted on 36 patients presenting with acute ischemic stroke who were going through digital subtraction angiography from March 2017 to March 2018.Collateralization status after unilateral or bilateral stenosis was evaluated.Modified ranking scale (mRS) score was measured on the first day of the stroke and after three months.The disability of ischemic stroke patients was compared between patients who developed collateralization and who had not.Among them, 61.6% developed collateralization.Among the patients who developed collateralization after three months, 90.9% patients had mRS scale of ≤2 and who not developed collateralization, 85.7% patients had mRS scale of ≤2.In both the groups, the p value was <0.05.It can be concluded that carotid stenosed patients who suffered from ischemic stroke, most of the patients disability improved to some extents whether collateralization developed or not among the major vessels.

Prognosis of ischemic stroke patients with or without collateralization after carotid stenosis
Subash Kanti Dey, Md.Shahidullah, Anis Ahmed, Ahsan Habib and Abu Nasar Rizvi from complete recovery to complete loss of tissue and function.This diversity is partly explained by the compensatory ability of the collateral circulation and the ensuing cerebral blood flow. 13The collaterals are the pial arterioles connecting two major cerebral arteries that supply two different vascular territories.These arteriolar connections contribute to the retrograde filling of pial arteries distal to an occlusion, and they provide alternative routes for blood flow in the setting of acute ischemic stroke.There is a wide interindividual variability in the size, number, and localization of the collaterals. 14ecent evidence suggests that these collaterals are dynamic, with a time-dependent recruitment of flow to the symptomatic hemisphere, once major occlusion has occurred. 15Although conventional angiography is considered the gold standard for the collateral flow assessment, 16, 17 there is wide variation in how leptomeningeal collateral grade is graded 18-20 variables beyond a single measure of percent stenosis and the influence of collateral flow on stroke risk have not been explored.The association of collateral flow with hemodynamic variables and subsequent infarct size or stroke severity are also unknown.We, therefore, studied the potential impact of such extensive variability in collateral status on modifying the stroke risk due to intracranial atherosclerosis and the possible influen-ce on subsequent stroke characteristics.
The objectives of the study was to see the prognosis of ischemic stroke patients due to collateralization after unilateral or bilateral carotid stenosis.

Materials and Methods
This study was done on the ischemic stroke patients admitted in the inpatient Department from March 2017 to March 2018.Digital subtraction angiography was done in the catheter laboratory.From the report, information regarding completeness of circle of Willis and details of collateralization were obtained according to the specified objectives.The severity of the stroke was assessed by mRS scale first at the time of registration and after three months.mRS score of the patients of ischemic stroke who had carotid stenosis were compared between the groups with collateralization and without collateralization.mRS scale of <2 was categorized as normal and mRS scale >2 was categorized as disease or disable.

Statistical analysis
The difference of disability between the groups was tested by McNemar test.

Results
Table I shows that the most frequent age group was 56-65 years representing 45.5% who developed collateralization after stroke but 57.1% was not developed.
Table I shows that 81.8% stroke patients developed collateralization but 85.7% not, who also suffered from hypertension.It was not statistically significant.But patients who had history of previous stroke, 54.5% patients developed collateralization which was statistically significant (p<0.05).

Discussion
In this study, the most frequent age group was 56-65 years.Among them, 45.5% developed collateralization after stroke, though it was not statistically significant.One study showed older age group (mean age 66.9 ± 11.6 years) developed less collateral. 10  This study suggests that composite antegrade and collateral assessment is feasible and useful in the prognostication of patients with chronic carotid stenosis.Some study previously showed leptomeningeal collateral play an important role after ischemic stroke and results in good outcome. 18ven in acute stroke patients good outcome was found after revascularization in presence of good collateral. 6, 9One study found infarct volume was depended on collateral. 19The effect of corticocortical collateralization was evaluated on the prognosis of stroke.In case of proximal and distal intracranial stenosis of internal carotid artery, outcome depends on collateralizations. 7, 12, 14, 20,21Prognosis was not significantly associated with antegrade or collateral grade per se. 11The favorable neurological outcomes among patients with good collateral compensation could be linked to the neuroplasticity theory.Neuroplasticity in poststroke by synaptogenesis or dendritic arborization. 22n animal model demonstrated restoration of perfusion to ischemic borders by collateral circulation via arterioles and new capillaries in Wistar rats after surgical ligation of MCA branches. 23Collateral circulation potentially provides blood supply to the perilesional brain parenchyma to facilitate repair and recovery, and may partially explain why patients with good collateral flow had better neurological recovery. 24

Conclusion
Carotid stenosed patients who suffered from ischemic stroke, improved to some extent whether collateralization developed among major vessels or not.