Moyamoya disease

Moyamoya disease

Moyamoya disease

Moyamoya disease 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).

A collateral circulation develops around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to bleeding, aneurysm and thrombosis. On conventional X-ray angiography, these collateral vessels have the appearance of a "puff of smoke" (described as "もやもや (moyamoya)" in Japanese).

When moyamoya is diagnosed by itself, with no underlying correlational conditions, it is diagnosed as moyamoya disease. This is also the case when the arterial constriction and collateral circulation are bilateral. Moyamoya syndrome is unilateral arterial constriction, or occurs when one of the several specified conditions is also present.  This may also be considered as moyamoya being secondary to the primary condition. Mainly, occlusion of the distal internal carotid artery occurs. On angiography, a "puff of smoke" appearance is seen, and the treatment of choice is surgical bypass.

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Cause

About 10% of cases of moyamoya disease are familial, and some cases result from specific genetic mutations. Susceptibility to moyamoya disease-2 (MYMY2; 607151) is caused by variation in the RNF213gene (613768) on chromosome 17q25. Moyamoya disease-5 (MYMY5; 614042) is caused by mutation in the ACTA2 gene (102620) on the long arm of chromosome 10 (10q23.3); and moyamoya disease-6 with achalasia (MYMY6; 615750) is caused by mutation in the GUCY1A3 gene (139396) on the long arm of chromosome 4 (4q32). Loci for the disorder have been mapped to the short arm of chromosome 3(MYMY1) and the long arm of chromosome 8 (8q23) (MYMY3; 608796). See also MYMY4 (300845), an X-linked recessive syndromic disorder characterized by moyamoya disease, short stature, hypergonadotropic hypogonadism, and facial dysmorphism. and linked to q25.3, on chromosome 17. (Online Mendelian Inheritance in Man, omim.org/entry/252350).

In Japan the overall incidence is higher (0.35 per 100,000). In North America, women in the third or fourth decade of life are most often affected, but the condition may also occur during infancy or childhood. These women frequently experience transient ischaemic attacks (TIA), cerebral hemorrhage, or may not experience any symptoms at all. They have a higher risk of recurrent stroke and may be experiencing a distinct underlying pathophysiology compared to patients from Japan.

Moyamoya disease can be either congenital or acquired. Patients with Down syndrome, sickle cell anemia, neurofibromatosis type 1, congenital heart disease, fibromuscular dysplasia, activated protein Cresistance, or head trauma can develop moyamoya malformations. It is more common in women than in men, although about a third of those affected are male.

Diagnosis

The diagnosis of moyamoya is suggested by CT, MRI, or angiogram results. Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease. MRI and MRA should be performed for the diagnosis and follow-up of moyamoya disease. Diffusion-weighted imaging can also be used for following the clinical course of children with moyamoya disease, in whom new focal deficits are highly suspicious of new infarcts.

Proliferation of smooth muscle cells in the walls of the moyamoya-affected arteries has been found to be representative of the disease. A study of six autopsies of six patients who died from moyamoya disease lead to the finding that there is evidence that supports the theory that there is a thickening, or proliferation, of the innermost layer of the vessels affected by moyamoya. These vessels are the ACA (anterior cerebral artery), MCA (middle cerebral artery), and ICA (internal carotid artery). The occlusion of the ICA results in concomitant diminution of the "puff-of-smoke" collaterals, as they are supplied by the ICA.

Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease. Conventional angiography provided the conclusive diagnosis of moyamoya disease in most cases and should be performed before any surgical considerations.

Dr. Darren B. Orbach, MD, PhD explains how the disease progresses as well as the role angiography plays in detecting the progression of Moyamoya in a short video 

 

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Associated biomarkers

Smith (2015) conducted a study that looked into specific biological markers that correlate to moyamoya disease. Some of the categories of these biomarkers include phenotypes - conditions commonly related to moyamoya, radiographical markers for the diagnosis of moyamoya, and proteins as well as cellular changes that occur in cases of moyamoya.

Similar to Moyamoya disease, there are conditions that are closely associated with Moyamoya disease. Some of the more common medical conditions that are closely associated with Moyamoya disease include trisomy 21 (Down's Syndrome), sickle cell disease, and neurofibromatosis type 1. There is also evidence that identifies hyperthyroidism and congenital dwarfing syndromes as two of the more loosely associated syndromes that correlate with the possibility of being diagnosed with Moyamoya disease later in life.

There is also research that has shown that certain radiographic biomarkers that lead to the diagnosis of moyamoya disease have been identified. The specific radiographic markers are now considered an acceptable key component to Moyamoya Disease and have been added to the International Classification of Diseases (ICD). These biomarkers of moyamoya are "stenosis of the distal ICA's up to and including the bifurcation, along with segments of the proximal ACA and MCA...dilated basal collateral vessels must be present"  Some other common findings that have not been added to the classification index of those with moyamoya disease which are found using radiography involve very distinct changes in the vessels of the brain. These changes include newly formed vessels made to compensate for another change noted, ischemia and cerebrovascular reserve, both found on MRI. Functional changes include evidence of ischemia in vessels of the brain (ICA, ACA, MCA, specifically). It is important to also note that the radiographic biomarkers, in order to be classified as moyamoya disease, all findings must be bilateral. If this is not the case and the findings are unilateral, it is diagnosed as Moyamoya Syndrome. 

There are also several protein biomarkers that have been linked to the Moyamoya disease diagnosis. Although the sample size of the studies performed are small due to the rarity of the disease, the findings are indicative of a correlation between the disease and several specific protein biomarkers. Other studies have confirmed the correlation of Moyamoya and adhesion molecule 1 (ICAM-1) being increased as compared to normal vascular function counterparts. Furthermore, it has been concluded that the localization of inflammatory cells suggests that the inflammation stimulus iteself may be responsible for the proliferation and occlusion in the ICA, ACA, and MCA found in those with Moyamoya disease. 

Treatment

There is no cure for this disease. Drugs such as antiplatelet agents (including aspirin) are usually given to prevent clots, but surgery is usually recommended. Since moyamoya tends to affect only the internal carotid artery and nearby sections of the adjacent anterior and middle cerebral arteries, surgeons can direct other arteries, such as the external carotid artery or the superficial temporal artery to replace its circulation. The arteries are either sewn directly into the brain circulation, or placed on the surface of the brain to reestablish new circulation after a few weeks.

There are many operations that have been developed for the condition, but currently the most favored are the in-direct procedures EDAS, EMS, and multiple burr holes and the direct procedure STA-MCA. Direct superficial temporal artery (STA) to middle cerebral artery (MCA) bypass is considered the treatment of choice, although its efficacy, particularly for hemorrhagic disease, remains uncertain. Multiple burr holes have been used in frontal and parietal lobes with good neovascularisation achieved.

The EDAS (encephaloduroarteriosynangiosis) procedure is a synangiosis procedure that requires dissection of a scalp artery over a course of several centimeters and then making a small temporary opening in the skull directly beneath the artery. The artery is then sutured to a branch of the middle cerebral artery on the surface of the brain and the bone is replaced.

In the EMS (encephalomyosynangiosis) procedure, the temporalis muscle, which is in the temple region of the forehead, is dissected and through an opening in the skull placed onto the surface of the brain.

In the multiple burr holes procedure, multiple small holes (burr holes) are placed in the skull to allow for growth of new vessels into the brain from the scalp.

In the STA-MCA procedure, the scalp artery (superficial temporal artery or STA) is directly sutured to an artery on the surface of the brain (middle cerebral artery or MCA). This procedure is also commonly referred to as an EC-IC (External Carotid-Internal Carotid) bypass.

All of these operations have in common the concept of a blood and oxygen "starved" brain reaching out to grasp and develop new and more efficient means of bringing blood to the brain and bypassing the areas of blockage. The modified direct anastomosis and encephalo-myo-arterio-synangiosis play a role in this improvement by increasing cerebral blood flow (CBF) after the operation. A significant correlation is found between the postoperative effect and the stages of preoperative angiograms. It is crucial for surgery that the anesthesiologist have experience in managing children being treated for moyamoya, as the type of anesthesia they require is very different from the standard anesthetic children get for almost any other type of neurosurgical procedure.

10 common querstion about Moyamoya disease

1Is Moyamoya disease curable?
Moyamoya is a progressive disease that does not improve without treatment. While moyamoya itself is not curable, surgery to provide alternative blood flow to the brain prevents the symptoms related to moyamoya and can provide an excellent long term outcome with significant stroke risk reduction.
2Is Moyamoya disease fatal?
Without treatment, Moyamoya disease can be fatal as the result of intracerebral hemorrhage (bleeding within the brain). Without surgery, the majority of individuals with Moyamoya disease will experience mental decline and multiple strokes because of the progressive narrowing of arteries.
3What are the symptoms of Moyamoya disease?
Accompanying signs and symptoms of moyamoya disease related to reduced blood flow to the brain include: Headache. Seizures. Weakness, numbness or paralysis in your face, arm or leg, typically on one side of your body. Visual disturbances. Difficulties with speaking or understanding others (aphasia) Developmental delays.
4How is Moyamoya diagnosed?
Doctors can usually make a diagnosis of moyamoya if MRI images show 1) diminished blood flow in the internal carotid artery and the middle and anterior cerebral arteries and 2) prominent collateral blood flow at the base of the brain. To confirm the diagnosis of moyamoya disease, an angiogram is typically required.
5Is Moyamoya genetic?
The genetics of moyamoya disease are not well understood. Research suggests that the condition can be passed through families, and changes in one gene, RNF213, have been associated with the condition. Other genes that have not been identified may be involved in moyamoya disease.
6Does moyamoya run in families?
Researchers believe that Moyamoya disease is an inherited condition because it tends to run in families.
7How fast does Moyamoya progress?
The average follow-up after surgery was 5.3 years (3.1 years for adults and 5.6 years for children; range 1-16 years). During this period, 10 (30%) of 33 patients progressed to bilateral disease. The mean time until disease progression was 2.2 years (range 0.5-8.5 years).
8How do you treat moyamoya?
Your treatment may include: Medication. Medications may be prescribed to reduce the risk of stroke or to aid in seizure control, including: ... Revascularization surgery. Direct revascularization procedure for moyamoya disease. ... Other Surgery. ... Therapy. ... What you can do. ... What to expect from your doctor.
9What causes Moyamoya in adults?
The cause of moyamoya disease is unknown. The narrowing of the brain's blood vessels may be due to injuries or genetic abnormalities. There may be some links between the condition and neurofibromatosis, or to procedures such as X-rays of the skull or heart surgery, or treatments such as chemotherapy.
10What causes brain disease?
Some brain diseases, such as Alzheimer's disease, may develop as you age. They can slowly impair your memory and thought processes. ... Neurodegenerative diseases Huntington's disease. ALS (amyotrophic lateral sclerosis), or Lou Gehrig's disease. Parkinson's disease. all forms of dementia.

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