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3 Cerebrovascular Surgeries that Benefit from Flow Measurements

By Susan Eymann, MS22 Jun 2022

Cerebrovascular surgeries are elegant, demanding, and risky. They require utmost precision.

There are two basic reasons to perform a cerebrovascular procedure. One is to preserve or restore blood flow after the procedure. The second is to augment blood flow when there is a baseline flow deficiency.

Knowing true volume blood flow is key. Three cerebrovascular surgeries that use Transonic flow measurements are aneurysm clipping surgery, extracranial-intracranial (EC-IC) bypass for moyamoya, and arteriovenous malformation obliteration.

Each relies on Transonic volume flow measurements for valuable information to guide the procedure and confirm the procedure’s surgical success.

Intracranial Aneurysm Clipping

Rupture of intracranial aneurysms affects about 30,000 people each year in the U.S. Up to 10% of these patients die before reaching the hospital. Only half survive aneurysm rupture.

The tried-and-true treatment for cerebral aneurysms is clipping where the surgeon meticulously applies a titanium clip to the base of the aneurysm to block blood flow into the aneurysm and eliminate its risk of hemorrhage.

Transonic intraoperative flow measurements are used during this procedure before clipping to ascertain a baseline flow measurement, and after the aneurysm is clipped. If flow after clipping is similar to baseline flow, the surgeon knows that cerebral flow has not been compromised.

If flow drops 25% or more, flow measurements prompt the surgeon to reposition the clip until flow in the parent vessel is fully preserved. By providing the surgeon with immediate, direct, quantitative feedback on blood flow in the vessels at risk during aneurysm surgery, Transonic flow measurements ensure the safe progression of the surgery and help avoid a devastating intraoperative stroke. 

EC-IC Bypass for Treatment of Moyamoya Syndrome

Moyamoya is a progressive disease in which the walls of cerebral arteries around the Circle of Willis thicken, stenose, and occlude. Tiny collateral vessels form that appear on an angiogram as puffs of smoke (Moyamoya in Japanese) to compensate for the obstructed cerebral flow.

Oxygen deprivation resulting from inadequate blood supply causes typical moyamoya symptoms which include paralysis of the feet, legs, or the upper extremities, headaches, vision problems, and possible intellectual disability.

The disease occurs worldwide. In children, it is characterized by the onset of one or more cerebral ischemic events. In adults, cerebral hemorrhages and strokes occur.

One treatment modality for moyamoya is direct surgical revascularization to augment flow in the cerebral territories. This is achieved with an extracranial-intracranial (EC-IC) bypass.

During this procedure, the superficial temporal artery (STA) is used as an extracranial bypass. It is cut, flow is measured, and a Cut Flow Index is determined. The STA and then connected to one or more of the intracranial cerebral arteries, typically, the middle cerebral artery (MCA).

Flow in the MCA is measured before and after anastomosis to confirm that flow has indeed been increased. This therapy is more commonly used in adults because their cerebral vessels are larger than those in children.

Arteriovenous Malformation (AVM) Obliteration

Arteriovenous malformations are masses of abnormal blood vessels that can grow in any area of the brain.

They consist of a nest of blood vessels where arteries connect directly to low-resistance veins rather than feeding into a capillary network to perfuse the territory of the brain. In 12% (36,000 of an estimated 300,000) of Americans with AVMs, the abnormality causes symptoms of varying severity. Loss of neurologic function depends on both the location of the AVM and the amount of bleeding.

Cerebrovascular surgery treats the AVM by totally excising the nest of blood vessels, thus keeping them from ever recurring. A Transonic perivascular micro-flow probe is used to measure flow in vessels, including arterial feeders, potential transit arteries, and venous drainages during different phases of AVM resection. The flow measurements help the surgeons understand the AVM architecture and guide its surgical planning and resection.

In these three examples of cerebrovascular surgeries, Transonic transit-time ultrasound intraoperative flow measurements have proven to be a feasible, safe, repeatable, and reliable methodology to assist surgery in its different phases.

Download our handbook Flow Assisted Surgical Technique (F•A•S•T) to learn more about quantitative, intraoperative measurements to improve surgical outcomes and manage cerebral disease.