Pial synangiosis

What is pial synangiosis?

Pial synangiosis is a type of revascularization surgery—a procedure that restores blood flow to parts of the body where arteries or veins have been narrowed or blocked. It is used to treat moyamoya disease, and the goal of surgery is to improve blood flow to the brain by laying healthy tissue (usually from the scalp) on the surface of the brain to encourage new blood vessel growth and improve circulation. This technique is often chosen for children because it avoids the risks of direct vessel connection in very small arteries while helping reduce the chance of future strokes. Many children who undergo this procedure can return to school and daily activities with a greatly improved quality of life.

Why is pial synangiosis performed?

Pial synangiosis is performed to improve blood flow in children with moyamoya disease, preventing further strokes and neurological damage. While medications such as acetylsalicylic acid and clopidogrel can reduce blood clotting risk by keeping certain cells in the blood (platelets) from sticking together, surgery is the only treatment for moyamoya disease that can restore blood circulation in the brain.

Possible risks

As with any brain surgery, there are risks, including bleeding, infection or temporary neurological changes. A small number of children may experience a stroke around the time of surgery. However, the overall risk of repeated strokes is much higher without surgery.

Before surgery

Your child will meet with the neurology and neurosurgery teams. They will undergo magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) scans, cerebral angiography and blood tests before the procedure. Your child will also meet the anesthesiology team to review the process of receiving general anesthesia. The care team will explain the surgery and answer your questions before asking for consent to perform pial synangiosis.

Your child will be admitted to the hospital a day or two prior to surgery for pre-operative hydration and to complete any additional testing/assessments.

For more information on how to prepare for surgery, see Coming for surgery.

How is pial synangiosis performed?

The surgeon will make a small opening in the skull to access the brain (craniotomy). A scalp artery (usually the superficial temporal artery) is then placed directly on the surface of the brain (pia mater). No direct connection of arteries is made; instead, over time, the artery will naturally grow tiny branches into the brain tissue, creating a new source of blood flow.

Safety considerations

Unlike other revascularization techniques, pial synangiosis avoids manipulating very small brain arteries directly, which reduces some of the risks of surgery in children. The body’s natural healing process is used to form new blood vessels over weeks to months.

Immediate care after the procedure

After surgery, your child will spend some time in the recovery unit or intensive care for close monitoring. The health-care team will check your child’s neurological function frequently and manage your child’s hydration levels to maintain their blood volume and blood pressure. Most children remain in hospital for several days. Pain and swelling will be managed with medication.

Complications to watch for after the procedure

Rare complications during recovery include infection, seizures, or stroke.

At home, seek urgent medical attention if your child develops new weakness, speech problems, or seizures. An easy way to remember the signs of stroke is the BE FAST checklist:

• Balance – sudden loss of balance or coordination
• Eyes – sudden vision loss or double vision
• Face – face drooping or uneven smile
• Arm – weakness or numbness in an arm (or leg)
• Speech – slurred speech, difficulty speaking or trouble understanding words
• Time – call 911 right away. Every minute counts.

Caring for your child after surgery

Once home, your child should avoid strenuous activities for several weeks. Encourage good hydration and regular meals. Your child’s teachers and school can offer support with your child’s gradual return to learning.

For more information on how to care for your child after surgery, see Craniotomy.

Clinic visits and long-term outcomes

After pial synangiosis, your child will be followed by a combined neurology and neurosurgery team that provides coordinated care. The team also works closely with other services, such as anesthesia, genetics and rehabilitation, to support recovery and long-term health.

Follow-up includes repeat MRI/MRA scans to monitor new blood vessel growth and cerebral angiography several months after surgery to confirm that blood flow has improved. Most children experience fewer or no strokes after successful surgery, and their long-term outlook is greatly improved.

When to seek medical attention

Go to the nearest Emergency Department or call 911 if your child has sudden neurological symptoms (weakness, numbness, speech problems, vision loss, seizures or loss of consciousness, persistent vomiting, persistent headache) or you have concerns about their wound site. An easy way to remember the signs of stroke is the BE FAST checklist:

• Balance – sudden loss of balance or coordination
• Eyes – sudden vision loss or double vision
• Face – face drooping or uneven smile
• Arm – weakness or numbness in the arm (or leg)
• Speech – slurred speech, difficulty speaking or trouble understanding words
• Time – call 911 right away. Every minute counts.

At SickKids

Children with moyamoya disease are seen in a combined neurology and neurosurgery moyamoya clinic. This clinic brings together stroke neurologists and neurosurgeons, so families can receive coordinated care and treatment planning. The team also works closely with genetics, rehabilitation, and other specialists to support long-term care.

For appointments, please visit Neurology or contact the Neurosurgery Clinic.

Resources

American Stroke Association
www.stroke.org

National Organization for Rare Disorders (NORD)
www.rarediseases.org

Orphanet Moyamoya Disease
www.orpha.net

The Moyamoya Foundation
www.moyamoya.org

International Pediatric Stroke Organization (IPSO)
www.internationalpediatricstroke.org/

Boston Children’s Hospital Moyamoya Program
www.childrenshospital.org/services/moyamoya-program

Children’s Hospital of Philadelphia: Moyamoya Disease
www.chop.edu/conditions-diseases/moyamoya-disease

References

Scott R.M., & Smith E.R. (2009). Moyamoya Disease and Moyamoya Syndrome. New England Journal of Medicine. 360(12), 1226–1237. https://doi.org/10.1056/NEJMra0804622

Guzman, R., & Steinberg, G.K. (2010). Direct Bypass Techniques for the Treatment of Pediatric Moyamoya Disease. Neurosurgery Clinics of North America. 21(3), 565–573. https://doi.org/10.1016/j.nec.2010.03.013

Kleindorfer D.O., Towfighi A., Chaturvedi S., Cockroft K.M., Gutierrez J., Lombardi-Hill D., Kamel H., Kernan W.N., Kittner S.J., Leira E.C., Lennon O., Meschia J.F., Nguyen T.N., Pollak P.M., Santangeli P., Sharrief A.Z., Smith S.C. Jr, Turan T.N., Williams L.S. (2021). Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack: A Guideline From the American Heart Association/American Stroke Association. Stroke. 52(7), e364–e467. https://doi.org/10.1161/STR.0000000000000375. Erratum in: Stroke. 2021. 52(7), e483–e484. https://doi.org/10.1161/STR.0000000000000383