Through the course of her research and clinical work on pediatric strokes, Johns Hopkins neurologist Lisa Sun has found herself building expertise on a disease that’s rarely seen — and that is little understood — in the United States. 

Sun, who is at the Johns Hopkins Pediatric Stroke and Neurovascular Center, is at the forefront of research and treatment regarding moyamoya disease, a blood vessel disorder characterized by progressive narrowing and blockage of internal carotid arteries. The condition can lead to reduced blood flow to the brain, increasing risk of strokes and other neurological impairments.

Sun first grew interested in pediatric moyamoya during her fellowship in vascular neurology at the Johns Hopkins University School of Medicine, when she was deeply affected by the death of a young patient from the disease.

“The patient had a particularly strong impact on me, because I could never stop thinking about what could have happened if her condition had been properly recognized earlier,” says Sun, who is now an associate professor of neurology and associate program director of the pediatric neurology residency program at Johns Hopkins. “I saw this was an open area of research that really needs more work. And every time we have a new diagnosis of moyamoya, I’m reminded of all the challenges it poses and all the unknowns out there.” 

Frequently found in East Asia, where it is the most common cause of stroke in children, moyamoya appears more rarely in the United States, affecting approximately 0.9 per 1 million people. The term “moyamoya” is Japanese for “puff of smoke,” referring to the way the fragile, abnormal blood vessels appear in angiograms.

Johns Hopkins, one of the few medical institutions in the U.S. that specializes in treating moyamoya, saw only about 70 cases of pediatric moyamoya from 2003 to 2019, according to Sun’s data.

Moyamoya is typically diagnosed with imaging studies such as MRI and cerebral angiogram. But Sun is particularly interested in the potential of transcranial doppler (TCD) — an ultrasound-based technology that uses sound waves to measure blood flow in the brain — to catch moyamoya early for high-risk pediatric patients, which include children with sickle cell anemia, trisomy 21 and neurofibromatosis.

“TCD is an established technology that’s routinely used in children with sickle cell disease, but we haven’t utilized it much as a screening tool for moyamoya,” Sun says. “It’s an appealing option to investigate, because the main method we use now — MRI — comes with risks associated with anesthesia for children with moyamoya.” 

Treatments for moyamoya include medications to prevent blood clots, treatment of anemia and other stroke risk factors, and optimizing blood pressure and hydration. But in many cases, revascularization surgery — a delicate procedure to build a new blood supply to the brain — is the best solution.

“Moyamoya can be very impairing, and there is no cure, but we have treatments that, if instituted early enough, can significantly reduce the risk of stroke and bleeding in the brain,” Sun says.

Though revascularization surgery decreases long-term risks of stroke, it comes with the cost of increasing risk of stroke during the perioperative period. Sun recently led a study on this phenomenon, aiming to find areas of consensus among 30 neurologists and other specialists in North America with expertise in moyamoya. The study found many areas of agreement, such as the importance of good hydration and pain control around the time of surgery. It also identified a few major research priorities for the future, including understanding the ideal postoperative blood pressure and hemoglobin levels, and studying the importance of supplemental oxygen and continuous electroencephalography immediately after surgery. 

Another recent study Sun led, aiming to understand modifiable risks for perioperative stroke among pediatric patients with moyamoya, identified anemia as a major risk factor — an exciting finding, she says, and an area that demands more research. 

“The knowledge gaps on moyamoya are where I’ve targeted a lot of my research at Hopkins,” she says, “so we can better understand and inform how we should be caring for these children.”

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