Novel Imaging Techniques Provide Insight into Pediatric Patients

by Adrienne Mueller, PhD
September 19, 2023

Stroke is a debilitating disorder that affects a large proportion of the population. In the US, someone dies of stroke every 3 minutes and 14 seconds. Patients who have cerebrovascular diseases – problems that affect the vasculature and blood flow in the brain – are at a high risk of stroke. A common mechanism of stroke is loss of blood flow to an area of the brain by the blockage of constricting of blood vessels. When that happens, blood flow needs to change to adapt to the loss passage through that vessel. The capacity of cerebral blood flow to change is called ‘cerebrovascular reserve’. The lower a patient’s cerebrovascular reserve, or ability to adapt to decreased blood flow, the higher their risk of stroke.

Moyamoya disease is a chronic cerebrovascular disorder that causes blockages in cerebral blood vessels. The disease begins in childhood and worsens over time. A hallmark of Moyamoya disease is impaired cerebrovascular reserve, and its associated increase in stroke risk. In Moyamoya patients, a bypass surgery procedure can stabilize and restore blood flow to regions affected by the blockages. In adults, this procedure improves cerebrovascular reserve and reduces the risk of stroke. However, previous research has not determined whether pediatric patients with the same disorder also benefit from improved hemodynamics. Determining whether pediatric Moyamoya patients experience the same changes in blood flow dynamics as adult patients has important implications for treatment.

In a recent study reported in the Journal of Magnetic Resonance Imaging, a team of Stanford researchers led by Moss Zhao, DPhil, Elizabeth Tong, MD, Gary Steinberg MD, PhD, and Greg Zaharchuk, MD, PhD, used a new quantitative magnetic resonance imaging (MRI) technique to non-invasively measure blood flow in pediatric Moyamoya patients and assess their response to bypass surgery.

Bypass surgery caused an increase in cerebral blood flow in a representative pediatric patient with Moyamoya disease. Left shows blood flow pre-surgery, right show blood flow post-surgery.

The investigators studied the outcomes of 46 pediatric patients with Moyamoya disease using a novel MRI technique called arterial spin labeling that is both non-invasive and safe for pediatric populations. They scanned the brains of patients before and after surgical intervention and measured the cerebrovascular reserve, which they defined as the percent change in cerebral blood flow. The investigators found that bypass surgery caused a significant increased cerebral blood flow both one week and also 6 months after

surgery, and that cerebrovascular reserves were increased by an average of 68%. Their study therefore demonstrated that bypass surgery is also effective in pediatric Moymoya patients: showing for the first time that there are both short- and long-term improvements in cerebral blood flow in this vulnerable patient population.

Additional Stanford Cardiovascular Institute-affiliated investigators who contributed to this study include Ryu Duarte Armindo, Ates Fettahoglu, Jason Choi, Jacob Bagley, Kristen W. Yeom, and Michael Moseley.