Moyamoya disease: what it is, symptoms, diagnosis and treatment

The Stroke Association describes moyamoya as a condition in which the main arteries in the brain become narrowed, limiting blood flow. The body responds by growing a network of small, fragile blood vessels to try to supply the brain. On a brain scan these vessels look like a puff of smoke, which is what moyamoya means in Japanese.

The Stroke Association says that when it occurs on its own in an otherwise healthy child, it is known as moyamoya disease, while moyamoya syndrome describes the same arterial changes in the presence of another condition. Birmingham Women's and Children's NHS Foundation Trust says the condition is progressive and, left untreated, can cause strokes, seizures, paralysis, brain damage and can be fatal. It says it affects about one person in every million.

The Stroke Association says moyamoya does not always have symptoms, but it can cause headaches, slurred speech and weakness on one side of the body. It can lead to strokes and transient ischaemic attacks (TIA or mini-strokes) in some children.

Birmingham Women's and Children's NHS Foundation Trust lists strokes, seizures, paralysis and brain damage as consequences if the condition is left untreated.

Moyamoya can cause stroke, so the signs matter. The NHS says the main symptoms of a stroke can happen suddenly and include face weakness (one side may droop), arm weakness (you may not be able to lift both arms and keep them there) and speech problems (slurred or confused speech). It uses the word FAST: face, arms, speech and time to call 999.

Other signs listed by the NHS include weakness or numbness down 1 side of the body, blurred vision or loss of sight, difficulty speaking or thinking of words, confusion, dizziness or falling over, a severe headache and nausea or vomiting. It says symptoms can sometimes stop after a short time, but you should still get medical help straight away.

The Stroke Association adds that children may have other signs, including sudden severe headache, seizures, new vertigo or confusion, problems with walking or balance, neck pain or stiffness, drowsiness or loss of consciousness, and changes in sensation such as pins and needles. It says to call 999 straight away if you suspect a stroke in a child.

The Stroke Association says moyamoya has been found in children with sickle cell disease, Down syndrome and neurofibromatosis. It says there are also certain genes associated with a predisposition towards moyamoya, and that it sometimes occurs in otherwise healthy children.

If you are concerned about family risk, a clinical genetics team can advise.

The name itself refers to the typical appearance on imaging. The Stroke Association says moyamoya means "puff of smoke" and refers to the appearance of the abnormal blood vessels in the brain scan image. Birmingham Women's and Children's NHS Foundation Trust describes the new vessels as wispy and smoke-like on an X-ray.

For stroke in general, the NHS says doctors do tests such as blood tests, CT, MRI and ultrasound scans to check in and around the brain, and an ECG to check the heart, and these tests can show what type of stroke has happened. A specialist neurology and neurosurgery team decides which tests suit each person.

Birmingham Women's and Children's NHS Foundation Trust quotes a consultant neurosurgeon who says that currently there is no effective drug that can prevent the narrowing of the vessels that reduce blood flow to the brain. Surgery is the main treatment.

The trust describes a procedure called pial synangiosis, which it calls the gold standard for children with the disease. The surgeon exposes a healthy scalp artery (the superficial temporal artery), opens a window of bone beneath it, and places the artery directly on the surface of the brain so that new blood vessels grow from it and provide a vital new blood supply. It says it usually takes three to four hours for each brain hemisphere. The family featured in its report also had regular check-ups afterwards.

The same article says that for the previous ten years all moyamoya patients in its region had been sent to Great Ormond Street Hospital for surgery, and Royal Manchester Children's Hospital says its neurosurgery unit has special expertise in managing moyamoya and other neurovascular diseases. Surgery for moyamoya is done in a small number of specialist centres.

The Stroke Association says the causes of stroke in children are very different from those in adults, that strokes can affect previously healthy children, and that in around 1 in 10 cases there is no identified cause. It lists heart disorders, blood disorders, infections and vascular disorders as the main groups of risk factor.

Call 999 straight away if you think you or a child is having a stroke, with face, arm or speech problems, sudden severe headache, seizure, or loss of consciousness. The NHS says to call 999 now if you think you are having or have had a stroke, or have had signs of a stroke within the last 24 hours even if they have stopped. Do not drive yourself to A&E.

If moyamoya has been diagnosed, follow the emergency plan your specialist team gave you, and ask what to do if symptoms recur.

On the NHS, moyamoya is usually diagnosed in a hospital stroke or neurology service and managed in a specialist neurosurgery centre, including children's units for young patients. Because it is rare, referral is often between centres. If you are considering a private opinion, ask which specialist centre will do any surgery and how follow-up will be shared with your GP.