Moyamoya disease is a rare disorder of the carotid arteries - the arteries that supply blood to the brain. The term 'Moyamoya' means 'puff of smoke'. It refers to the appearance of arteries on a cerebral angiogram. The condition was first described in Japan, and, since then has been described in other parts of the world.
What is Moyamoya disease?
In this condition, the carotid arteries that supply blood to the brain become thickened and narrowed gradually over time. As a result, the brain does not receive enough oxygen-rich blood. To compensate for the reduced supply, the body grows new arteries around the head and brain. These new arteries, also called the 'Moyamoya vessels' try to compensate for the reduced blood flow. However, these new vessels never fully compensate for the reduced blood supply. They also have a propensity to bleed easily.
Who does Moyamoya disease affect?
There are no community-based studies from India. The prevalence of the disease ranges from 3.2 to 10.5 per 100,000 population. In general, the disease has been found to be more prevalent among Asians and people of Asian origin. The exact cause of this disease is not known yet. About 57% of the affected patients are Asian and 71% are female. Although the disease may be seen in any age group, it is more common in people from 5-15 years and 30-40 years of age. Family history is present in about 10%-15% of the patients.
How does Moyamoya disease present?
All the symptoms of Moyamoya disease arise from reduced blood supply to the brain and/or rupture of the 'Moyamoya vessels'. Reduced blood supply may cause stroke and rupture of the unhealthy Moyamoya vessels cause bleeding within the brain. Adults experience haemorrhage more commonly; cerebral ischemic strokes from reduced blood supply are more common in children. Children may have weakness or numbness in an arm or leg, hemiparesis, monoparesis, involuntary movements, headaches, dizziness, or seizures. Mental retardation or persistent neurologic deficits may be present. Adults may have symptoms and signs similar to those in children, but haemorrhage (bleeding) of sudden onset is more common in adults.
How is it diagnosed?
The condition is diagnosed on MRI and cerebral angiography in a patient presenting with stroke or brain bleed.
Are there any associated conditions?
Many conditions are seen more commonly with Moyamoya like condition, although the exact cause-effect relationship has not been demonstrated. Some of the common conditions are:
- Radiotherapy to head and neck
- Down's Syndrome
- Neurofibromatosis type 1
- Sickle cell disease
- Congenital Heart Disease
Is there a treatment?
Since the exact cause of the disease is unknown, there is no treatment to reverse the narrowing. However, treatment is aimed at preventing stroke by administering aspirin and surgery that improves blood flow to the affected parts of the brain. Surgery is highly successful in preventing stroke and bleeding in future and is the mainstay of treatment. Without surgery, the majority of individuals with Moyamoya disease will experience mental decline and multiple strokes because of the progressive narrowing of arteries.
Tips for family and caregivers of patients with Moyamoya disease
Educating and supporting the child and family plays a key role. Not surprisingly, parents are shocked and frightened when they learn their children have had strokes, because they do not realize children can have strokes. Parents should be instructed to inform surgeons and anesthesiologists to avoid hyperventilation. Parents and children need to identify everyday events that may precipitate mini-strokes (also called Transient ischemic attacks). For example, one patient had a stroke while crying or singing a long note during practice. The precipitation of mini-strokes by everyday events is particularly stressful for parents, who may be reluctant to discipline their child for fear of causing a mini-stroke if the child cries. Some sports such as cricket and soccer that lead to hyperventilation, have a high risk of causing mini-strokes, and it may not occur to parents to keep their children out of these sports. Schools should be informed about the diagnosis and any restrictions on physical activity.
Educating the child and family about seizures is an important part of the care of moyamoya patients. As with other seizure patients, families should be told that brief seizures lasting a few minutes are not thought to be harmful, but medical help should be sought for longer seizures.
Emotional support and appropriate advice on pre and post-operative care of the patient is an important part of treatment to alleviate the fear, anxiety and uncertainty experienced by the family.