Defining MoyaMoya Disease
Moyamoya disease is a form of rare and progressive cerebrovascular disorder that causes blocked arteries at the base of a person's brain in an area known as the, 'basal ganglia.' The name, 'moymoya,' means, 'puff of smoke,' in Japanese and describes the appearance of the tangle of tiny vessels which form to compensate for the blockage that occurs. The disease was first described in Japan in the 1960's and since then has been found in people in Europe, Australia, America, as well as in Africa.
Moyamoya syndrome is a disease in which certain arteries in the brain are constricted. Blood flow is blocked by the constriction, and also by blood clots (thrombosis). Moyamoya can be either congenital or acquired. The condition is believed to be hereditary and linked to q25.3, on chromosome 17. Recent investigations have established that both moyamoya disease and arteriovenous fistulas (AVFs) of the lining of the brain, the dura, are associated with dural angiogenesis.
Moyamoya disease affects children primarily, although it can also affect adults. The first symptom to appear in children is often stroke or recurrent transient ischemic attacks, or TIA's, often referred to as, 'mini-strokes.' accompanied by paralysis or muscular weakness that affects on side of their body, or seizures. In adults, the disease most often presents a hemorrhage stroke due to recurring blood clots in the brain vessels that have been affected. People with the disorder can experience disturbed consciousness, sensory and cognitive impairments, speech deficits, aphasia, vision problems, and involuntary movements. Moyamoya tends to run in families and researchers believe that the disease is the result of inherited genetic abnormalities.
Moyamoya disease causes a thickening of the internal carotid arteries which supply blood to important areas of a person's brain. Due to the thickening of these arteries, the flow of blood to the person's brain slows and increases the likelihood of blood clot formation, both of which may lead to either strokes or TIA's. The condition leads to smaller blood vessels attempting to supply oxygen to oxygen-starved areas of the person's brain which were once served by arteries that have become narrowed. These smaller vessels are more fragile than arteries and can break and bleed into the person's brain causing hemorrhages. This can be more dangerous than anywhere else in a person's body as brain tissue becomes inflamed and irritated and the pressure inside the person's skull increases.
Symptoms of MoyaMoya Disease
Children with Moyamoya disease often come to either the emergency room or the hospital with symptoms of a stroke or weakness on one side of their body, impaired vision, or slurred speech. The symptoms can happen and then slowly subside. They may also suddenly appear and remain permanently.
At times the disease will cause the person to experience headaches or seizures; a sudden change in either behavior or consciousness, due to changes in their brain's electrical activity. Seizures resulting in involuntary movements, loss of consciousness, twitching, shaking, visual disturbances, or abnormal sensations can occur. Potential causes can include trauma, epilepsy, tumor, stroke, meningitis and hydrocephalus.
On rare occasion, brain hemorrhages occur in children with Moyamoya disease, although they happen more often in young adults with the disease. The majority of people affected by the disease have one form of the condition; it is very rare to find the childhood form of the disease evolve later in life to the hemorrhagic form of the disease. Symptoms of the hemorrhagic form of the disease include:
Diagnosing MoyaMoya Disease
The standard means of diagnosing Moyamoya disease, as well as for planning surgery, is through a cerebral angiogram. A dye is used that shows up on X-rays; the dye is fed into the person's carotid artery and a series of X-ray images are taken. The narrowed artery, as well as the proliferation of new blood vessels, appear in the resulting images that have been taken. While all angiograms present a certain amount of risk, the risks are slightly higher for children. It is essential to have a highly-skilled angiographic team performing these tasks. As an option, Magnetic resonance imaging, and occasionally computed tomography scans, provide initial indications of Moyamoya disease.
Treatment of MoyaMoya Disease
Aspirin as well as other anti-clotting medications may reduce the risk of a stroke in persons with Moyamoya disease - but the disease itself will continue to progress. There are a number of surgical solutions that have been effective at bypassing the narrowed artery, creating a new blood supply to the area of the person's brain that has been affected by the disease. One of these is referred to as, 'pial synangiosis,' during which a healthy blood vessel from the person's scalp is moved so that it runs under a section of the person's skull and is then stitched to the surface of their brain. The procedure does not require either severing or reconnecting the tiny scalp and brain arteries. This presents an important advantage, particularly in young children.
The transplanted artery grows a network of healthy new arteries, which then serve the oxygen-deprived areas of the person's brain. Research has demonstrated that growth factors circulating in cerebrospinal fluid encourage development of new blood vessels. While it might take three to six months to benefit from the surgery, the procedure is effective. Children who experience Moyamoya disease find it to be a better alternative than a direct bypass operation.
After the surgery, the majority of people stay in the hospital for around a week and then return in about a month and a half for a follow-up with their surgeon. Six months to a year after the surgery, an angiogram is performed to confirm the growth of new blood vessels where they are needed. Annual MRI scans afterwards are usually sufficient. For people who have experienced long-term damage due to strokes, treatment forms also focus on speech and physical therapies, as well as occupational therapy, to assist them with regaining their ability to cope and function with remaining disabilities.
Children usually respond better to surgery than adults, although the majority of people have no further strokes or other related issues after surgery. Without surgery, most people with Moyamoya disease experience mental decline and multiple strokes due to a progressive narrowing of the arteries. Without treatment, Moyamoya disease can be fatal as a result of intra-cerebral hemorrhage.