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Measuring Flow Records a 5-Fold Increase in Flow During Moyamoya Revascularization

By Susan Eymann, MS28 Mar 2024

Moyamoya is a rare, progressive cerebrovascular disease caused by blocked arteries at the base of the brain. Moyamoya, or “puff of smoke” in Japanese, describes the tangled appearance of tiny vessels that attempt to compensate for the blockage. Without treatment, children can experience one or more cerebral ischemic events. In adults, cerebral hemorrhages occur. But with the right treatment, patients can live healthy, normal lives.

There are two primary treatments for moyamoya. One is indirect where a section of an artery that is normally connected to the scalp is rerouted onto the surface of the brain. New blood vessels sprout (synangiosis) from this artery into the brain, restoring blood flow to the underlying ischemic area(s) of the brain.

The second treatment is direct surgical revascularization with an extracranial-intracranial (EC-IC) bypass. During this procedure, the superficial temporal artery (STA) is cut and then reconnected to one or more recipient intracranial cerebral arteries, typically the middle cerebral artery (MCA). This therapy is more commonly used in adults because their cerebral vessels are larger than those in children. A combination of both techniques is frequently used in adults.

In the largest single-center study, to date, for direct moyamoya revascularization,1 Stanford University cerebrovascular surgeons compiled hemodynamic data from 18 years (496 revascularization procedures in 292 patients) of surgical revascularizations to treat moyamoya disease. Both before and after completion of the EC-IC bypass, STA and MCA blood flows were measured with the Transonic Charbel Micro-Flowprobe®. After bypass flow augmentation, MCA flow increased fivefold - mean flow of 23.9 +1.0 mL/min. The diameter of the STA bypass conduit was the main determinant for blood flow augmentation. High post-anastomosis middle cerebral artery (MCA) flow was associated with postoperative hemorrhage and transient neurologic deficits.

In a follow-up study of 19 consecutive patients at the University of Miami,2 the moyamoya EC-IC bypass surgery protocol was refined to anastomose the donor extracranial STA to two recipient cerebral arteries to perfuse two cerebral territories at the same time. The addition of the second anastomosis increased overall average bypass flow by 50%. The clinicians concluded that the one-donor, two- recipient technique allows a shorter dissection time while still preserving blood flow to the scalp. Routine use of intraoperative volumetric flow measurements in such surgeries provided a deeper understanding of the hemodynamic impact on individual patients.

In another study that included 97 surgeries,3 Japanese surgeons discovered that measuring intraoperative graft flow during EC-IC moyamoya bypass surgery may be an effective means of predicting hyperperfusion, a significant complication of direct bypass surgery for moyamoya disease that can cause temporary neurological deterioration or hemorrhagic stroke. Early detection could facilitate early therapeutic intervention.

In each of these studies, measuring blood flow intraoperatively with the Charbel Micro-Flowprobe enhanced intraoperative hemodynamic assessment that was integral to the revascularization protocol.


1Lee M, et al, “Intraoperative blood flow analysis of direct revascularization in patients with moyamoya disease,” J Cereb Blood Flow Metab. 2011 Jan;31(1):262-74. 

2Khan NR, Lu VM, Elarjani T, Silva MA, Jamshidi AM, Cajigas I, Morcos JJ. One-donor, two-recipient extracranial-intracranial bypass series for moyamoya and cerebral occlusive disease: rationale, clinical and angiographic outcomes, and intraoperative blood flow analysis. J Neurosurg. 2021 Aug 20;136(3):627-636.

3Nakamura A, Kawashima A, Nomura S, Kawamata T. Measurement of Intraoperative Graft Flow Predicts Radiological Hyperperfusion during Bypass Surgery in Patients with Moyamoya Disease. Cerebrovasc Dis Extra. 2020;10(2):66-75.