Moyamoya is a rare progressive disorder of the vessels in the brain. It results in narrowing or closing of the internal carotid/cerebral arteries that hinder supply of oxygen to the brain. In order to compensate for the decreased supply the collateral blood vessels are formed to supply blood to the brain. These collaterals are more fragile or weaker than the normal vessels and have more chances of tearing and bleeding inside the brain. These collaterals on an angiogram have a smoky/hazy appearance. It was first described by Japanese and named moyamoya that means to puff smoke in Japanese. Moyamoya can affect both sides of the brain and also lead to formation of aneurysms.
How To Prevent Moyamoya?
The diagnosis is established on the basis of MRA (magnetic resonance angiogram), computed topography angiography, CT perfusion and cerebral blood flow studies. Prevention of moyamoya is basically done by preventing the recurrent strokes and TIAs. The narrowing of the arteries cannot be stopped or reversed even with treatment, but with the use of blood thinners formation of clots that block the arteries can be prevented. Aspirin is widely used to reduce the risk of strokes. Treatment also involves the use of surgical treatments to provide for a new blood supply to the affected areas for the brain. The surgeries mostly use either direct bypass route performed in older people whereas indirect procedures are done in children below the age of 10 years.
Cerebral bypass procedure is done for revascularization of the brain by using a blood vessel from outside to connect to the vessel from inside the brain. This procedure is most commonly used where the superficial temporal artery is anastomosed with the middle cerebral artery and this provides improvement in blood circulation immediately.
EDAS is an indirect procedure where the superficial temporal artery is put in the brain’s surface and with time angiogenesis occurs that results in formation of small vessels that supply blood to the brain. EMS, EDAMS, omental transposition and multiple burr holes procedure are also other indirect bypass procedures used for revascularization.
The long term outlook for the people with moyamoya depends on the damaging risks of multiple strokes and transient ischemic attacks. The strokes can lead to disabilities and rapid decline in the health of the patient. It has been seen that in 50 to 65% of the cases the disease has progressed rapidly and had poor outcomes. However, if a patient is treated surgically before suffering a stroke then the outcome is excellent for the patient even if he has a severe condition. But if the patient is not treated on time the disease will progress with time and irreversible neurological deficits can occur that will further deteriorate the condition of the patient.
Causes And Symptoms Of Moyamoya
The exact cause of moyamoya remains unknown; however it is seen to have a familial predisposition in about 10% of the cases. It is also known to be associated with diseases such as Down’s syndrome, neurofibromatosis type 1 and sickle cell disease. People who have undergone radiotherapy to the brain for brain tumors are also susceptible to developing moyamoya. It mostly affects children in the age group of 5-10 years and adults between 30 to 50 years. Children who suffer with moyamoya usually present with symptoms of diminished blood supply to the brain that includes headaches, seizure activity, and uncontrollable body movements and sometimes a delay in development can be seen.
In adults the symptoms mostly appear after the person suffers an ischemic (due to a blockage in the artery there is interruption in flow of oxygenated blood to the brain) or hemorrhagic stroke (collateral blood vessels burst and leak into the brain), that is also called as a transient ischemic attack. They lead to weakness/numbness of the upper and lower limbs. The patient might have difficulty in speech or might suffer paralysis on one side of the body. Headache along with seizures are also common symptoms.