Moyamoya Disease

What is Moyamoya Disease?

Moyamoya disease (also known as moyamoya syndrome) is a rare disorder that affects blood supply to the brain. It occurs when the blood vessels that supply oxygen to the brain gradually become narrower and it affects the vessels in the circle of Willis (located in the base of the brain) and the carotid arteries. As the arteries narrow, the oxygen supply decreases and this increases the risk of a blood clot or stroke. Moyamoya syndrome is one of the most common causes of juvenile strokes.

Moyamoya translates as puff of smoke in Japanese and it is so-called because of the appearance of blood vessels in the brain, which form in response to the arteries narrowing. Moyamoya syndrome is mainly found in children and it tends to affect people with Asian heritage.

What causes moyamoya disease?

Moyamoya disease is caused by the gradual narrowing and thickening of the carotid arteries. This reduces blood flow to the brain and in response, new blood vessels start to form and the circulation of blood takes a kind of detour. It is not fully understood why moyamoya disease develops but there is evidence to suggest that trauma could be a trigger and genetic factors may play a part. Sometimes, children with moyamoya disease also suffer from additional disorders, including sickle cell anaemia, Down’s syndrome and neurofibromatosis. Congenital heart disease (heart problems that are present from birth) may also increase the risk of moyamoya disease.

What are the symptoms?

In children with moyamoya syndrome, symptoms are often similar to those associated with a stroke and include:

  • slurred and slow speech
  • weakness on one side of the face (this may cause the face to droop)
  • headaches
  • seizures
  • blurred vision

Moyamoya syndrome can contribute to an increased risk of haemorrhages. Warning signs of bleeding include:

  • a severe headache, which may feel like a shooting or stabbing pain
  • disturbed vision
  • nausea
  • feeling numb

Who is affected?

Moyamoya syndrome is most commonly diagnosed is children, with the average age of diagnosis around 7 years old. However, it is possible for this syndrome to affect adults. Moyamoya syndrome is rare. It is most commonly found in children of Asian descent.

Diagnosing moyamoya disease

Imaging tests are used to confirm a diagnosis of moyamoya syndrome. Tests that may be ordered by doctors include:

  • MRI scan
  • CT scan
  • MRA (magnetic resonance angiogram) - this is used to look at the blood vessels in detail. An angiogram is designed to analyse circulation and it involves injecting a coloured dye into the blood vessels, which allows doctors to see how the blood circulates and check the condition of the blood vessels.

Treatment for moyamoya disease

Surgery is the most influential form of treatment for moyamoya syndrome. There are various surgical procedures that can be used and they help to improve blood flow to the brain by bypassing affected arteries and diverting blood supply to reduce the risk of strokes and haemorrhages.

Examples of surgical procedures include:

  • EDAS (encephaloduroarteriosynangiosis)
  • EMS (encephalomyosynangiosis)
  • Omental transposition
  • Dural inversion

These procedures are indirect treatments designed to encourage the growth of new blood vessels.

It is also possible to carry out direct procedures, including pial synangiosis, which is designed to improve blood flow throughout the brain. This procedure involves connecting a blood vessel from the scalp to a blood vessel in the brain.

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