Comparative flow rates based on MR NOVA of various types of extracranial to intracranial bypass. David Golombeck BA, Timothy G White 1Department
1 MD ,
Amir R Dehdashti
1 MD ,
David Langer
1 MD
of Neurosurgery, North Shore University Hospital, Northwell Health, Manhasset, NY, USA
INTRODUCTION MoyaMoya disease (MMD) is characterized by progressive stenosis of the intracranial internal carotid arteries and their proximal branches, possibly leading to ischemic or hemorrhagic stroke. MoyaMoya disease has a distinct look on angiography with abnormally dilated collateral vessels described as “something hazy, like a puff of cigarette smoke”. The signs and symptoms of MMD are a result of the decreased blood flow due to the stenotic internal carotid artery. Surgical revascularization, such as extracranialintracranial bypass, is an established treatment to relieve symptoms and slow the progression associated with MoyaMoya disease. The treatment for MMD includes both direct and indirect bypasses and among the direct bypass procedures, STA-MCA bypass is the surgery that is primarily performed. However, there are still currently no strong predictors or methods to demonstrate success. MR NOVA is a technique used to quantify the blood flow in cerebral vessels. Using MR NOVA, this study will examine the differences between preoperative and postoperative blood flow on patients receiving extracranialintracranial bypass.
OBJECTIVES The purpose of this study is to determine if there is a quantitative difference in total hemispheric flow (ACA/PCA/MCA) in patients with unilateral MoyaMoya disease between the disease and non-disease hemispheres as well as if that difference is corrected following a direct bypass procedure.
MATERIALS AND METHODS
FIGURE 1
This is one of the first studies to quantitatively measure the decrease in total hemispheric flow on the diseased side in patient with unilateral MoyaMoya disease as well as quantitatively demonstrate the presence and robust nature of the pial collaterals on the diseased side. Furthermore, the most significant finding of this study is that the post operative flow is normalized on the disease size and becomes more comparable to the healthy side in the setting of direct bypass.
A retrospective review of all patients who received direct and/or indirect extracranial-intracranial bypass and were evaluated pre-op with MR NOVA. Patients were excluded if they were receiving cerebral bypass for a reason other than MoyaMoya disease.
RESULTS In total, 35 patients with unilateral MoyaMoya disease were evaluated with a pre-op MR NOVA. The total hemispheric flow in the affected side was compared to the total hemispheric flow in the contralateral, unaffected side. There was a significant difference between the disease and non-disease total hemispheric flow (P<0.00001). Additionally, the flow in the pial collaterals on the ipsilateral side were significantly higher relative to the collaterals on the contralateral, unaffected side (P<0.01). Among the 35 patients who were evaluated with pre-op MR NOVA, 31 patients also received a post-op NOVA within one month of the bypass procedure. Flow ratios (total hemispheric flow on disease side/total hemispheric flow on the unaffected side) of the pre-op NOVAs and post-op NOVAs were compared. The flow ratio pre-op was 0.69 whereas the ratio post-op was 0.91. This represents a significant normalization of flow in the affected side that almost equals the flow of the unaffected, contralateral side following the operation (P<0.05).
CONCLUSIONS
FIGURE 2
These are important findings, because although it was known that there is decreased flow on the diseased side in patients with MoyaMoya disease and that ipsilateral collaterals are present, this study quantifies these findings. This study demonstrated that using direct extracranial-intracranial bypass, there is an almost immediate restoration of flow rate that is close to the contralateral side. Indirect extracranial-intracranial bypass must recruit new blood vessels and thus does not immediately normalize flow. Therefore, this study provides speculative evidence in favor of using the direct extracranial-intracranial bypass method instead of the indirect method.
Pre-op NOVA of a patient with unilateral MoyaMoya Disease showing no flow through the LMCA (Figure 1). Post-op NOVA of this patient demonstrates a patent bypass graft as well increased total hemispheric flow (Figure 2). Flow values are in ml/min.
While this study shows that MR NOVA can quantitatively describe the flow rates in a patient with MoyaMoya disease, further research must be done to determine the prognostic value of quantitatively examining the flow rates in patients undergoing direct bypass procedures.
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Contact: dgolombeck1@pride.hofstra.edu