Moya Moya Disease
Encyclopedia
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
).
The blood vessels develop collateral circulation
around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to hemorrhage, aneurysm
and thrombosis. On X-rays, these collateral vessels have the appearance of a "puff of smoke" ("moyamoya" in Japanese).
The disease causes constrictions primarily in the internal carotid artery
, which travels from the neck up inside the skull just under the brain in the cavernous sinus. At the Circle of Willis, the internal carotid artery flows into the middle cerebral artery
, which continues into the brain, and the anterior cerebral artery, which is part of the Circle of Willis. Moyamoya disease often extends to the middle and anterior cerebral arteries.
When the internal carotid artery becomes completely blocked, the fine collateral circulation that it supplies is obliterated. Patients often survive on the collateral circulation from the back (posterior) of the Circle of Willis, from the basilar artery
.
Drugs such as antiplatelet agents (e.g., 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. Although there is a 4% risk of stroke soon (30 days) after surgery, there is a 96% probability of remaining stroke-free over the next 5 years.
The constrictions of the arteries in moyamoya disease are unlike the constrictions in atherosclerosis
. In atherosclerosis, the inner layer (lumen
) of the arteries suffers an immune reaction, fills with inflammatory cells, and accumulates fatty cells and debris. In moyamoya, the inner layer of the carotid artery overgrows inward to constrict the artery, and the artery also fills with blood clots, which cause strokes.
It is a disease that tends to affect children and adults in the third to fourth decades of life. In children it tends to cause strokes or seizures. In adults it tends to cause strokes or bleeding. The clinical features are cerebral ischemia
(strokes), recurrent transient ischemic attack
s (TIAs), sensorimotor paralysis (numbness and paralysis of the extremities), convulsions and/or migraine
-like headaches. After an ischemic stroke, a hemorrhagic reperfusion stroke may occur. A hemorrhagic stroke may also stem from rupture of the weak neovascular vessel walls.
Once it begins, the process of blockage (vascular occlusion) tends to continue despite any known medical management. In some people this leads to repeated strokes and severe functional impairment or even death. In others, this blockage may not cause any symptoms.
Moyamoya can be either congenital or acquired. Patients with Down syndrome
, neurofibromatosis
, or sickle cell disease can develop moyamoya malformations. It is more common in women than in men, although about a third of those affected are male . Brain radiation therapy in children with neurofibromatosis increases the risk of its development.
, MRI, or angiogram
. In fact, the name derives from its angiographic image; the "puff of smoke," which is how moyamoya loosely translates from Japanese
, refers to the appearance of multiple compensatorily dilated striate vessels seen on angiography. 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.
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.
(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 inches and then making a small temporary opening in the skull directly beneath the artery. The artery is then sutured to the surface of the brain and the bone 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-synagiosis 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.
Once major strokes or bleeding take place, even with treatment, the patient may be left with permanent loss of function so it is very important to treat this condition promptly.
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
).
The blood vessels develop collateral circulation
Collateral circulation
Collateral circulation is when an area of tissue or an organ has a number of different pathways for blood to reach it. This is often as a result of anastamoses - branches formed between adjacent blood vessels....
around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to hemorrhage, aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
and thrombosis. On X-rays, these collateral vessels have the appearance of a "puff of smoke" ("moyamoya" in Japanese).
The disease causes constrictions primarily in the internal carotid artery
Internal carotid artery
In human anatomy, the internal carotid arteries are two major arteries, one on each side of the head and neck. They arise from the common carotid arteries where these bifurcate into the internal and external carotid artery, and they supply the brain....
, which travels from the neck up inside the skull just under the brain in the cavernous sinus. At the Circle of Willis, the internal carotid artery flows into the middle cerebral artery
Middle cerebral artery
-External links:*...
, which continues into the brain, and the anterior cerebral artery, which is part of the Circle of Willis. Moyamoya disease often extends to the middle and anterior cerebral arteries.
When the internal carotid artery becomes completely blocked, the fine collateral circulation that it supplies is obliterated. Patients often survive on the collateral circulation from the back (posterior) of the Circle of Willis, from the basilar artery
Basilar artery
In human anatomy, the basilar artery is one of the arteries that supplies the brain with oxygen-rich blood.The two vertebral arteries and the basilar artery are sometimes together called the vertebrobasilar system, which supplies blood to the posterior part of circle of Willis and anastomoses with...
.
Drugs such as antiplatelet agents (e.g., 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
External carotid artery
In human anatomy, the external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it bifurcates into the external and internal carotid artery.-Course:...
or the superficial temporal artery
Superficial temporal artery
In human anatomy, the superficial temporal artery is a major artery of the head. It arises from the external carotid artery when it bifurcates into the superficial temporal artery and maxillary 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. Although there is a 4% risk of stroke soon (30 days) after surgery, there is a 96% probability of remaining stroke-free over the next 5 years.
The constrictions of the arteries in moyamoya disease are unlike the constrictions in atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
. In atherosclerosis, the inner layer (lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
) of the arteries suffers an immune reaction, fills with inflammatory cells, and accumulates fatty cells and debris. In moyamoya, the inner layer of the carotid artery overgrows inward to constrict the artery, and the artery also fills with blood clots, which cause strokes.
It is a disease that tends to affect children and adults in the third to fourth decades of life. In children it tends to cause strokes or seizures. In adults it tends to cause strokes or bleeding. The clinical features are cerebral ischemia
Cerebral ischemia
Brain ischemia, also known as cerebral ischemia, is a condition in which there is insufficient blood flow to the brain to meet metabolic demand. This leads to poor oxygen supply or cerebral hypoxia and thus to the death of brain tissue or cerebral infarction / ischemic stroke...
(strokes), recurrent transient ischemic attack
Transient ischemic attack
A transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
s (TIAs), sensorimotor paralysis (numbness and paralysis of the extremities), convulsions and/or migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
-like headaches. After an ischemic stroke, a hemorrhagic reperfusion stroke may occur. A hemorrhagic stroke may also stem from rupture of the weak neovascular vessel walls.
Causes
The condition is believed to be hereditary and linked to q25.3, on chromosome 17 http://emedicine.medscape.com/article/1180952-overview#ClinicalCauses. 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 affected. These women frequently experience transient ischemic attacks (TIA), cerebral hemorrhage or no symptoms. They have a higher risk of recurrent stroke and may be experiencing a distinct underlying pathophysiology compared to patients from Japan. Data suggest a potential benefit with surgery if early diagnosis is made. The pathogenesis of moyamoya disease is unknown.Once it begins, the process of blockage (vascular occlusion) tends to continue despite any known medical management. In some people this leads to repeated strokes and severe functional impairment or even death. In others, this blockage may not cause any symptoms.
Moyamoya can be either congenital or acquired. Patients with Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
, neurofibromatosis
Neurofibromatosis
Neurofibromatosis is a genetically-inherited disorder in which the nerve tissue grows tumors that may be benign or may cause serious damage by compressing nerves and other tissues...
, or sickle cell disease can develop moyamoya malformations. It is more common in women than in men, although about a third of those affected are male . Brain radiation therapy in children with neurofibromatosis increases the risk of its development.
Diagnosis
The diagnosis is initially suggested by CTComputed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
, MRI, or angiogram
Angiogram
Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins and the heart chambers...
. In fact, the name derives from its angiographic image; the "puff of smoke," which is how moyamoya loosely translates from Japanese
Japanese language
is a language spoken by over 130 million people in Japan and in Japanese emigrant communities. It is a member of the Japonic language family, which has a number of proposed relationships with other languages, none of which has gained wide acceptance among historical linguists .Japanese is an...
, refers to the appearance of multiple compensatorily dilated striate vessels seen on angiography. Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal
Leptomeninges
In medicine, leptomeninges is a term used to refer to the pia mater and arachnoid mater, two of the membranes that surround the brain and the spinal cord....
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.
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.
Treatment
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 arterySuperficial temporal artery
In human anatomy, the superficial temporal artery is a major artery of the head. It arises from the external carotid artery when it bifurcates into the superficial temporal artery and maxillary artery....
(STA) to middle cerebral artery
Middle cerebral artery
-External links:*...
(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 inches and then making a small temporary opening in the skull directly beneath the artery. The artery is then sutured to the surface of the brain and the bone 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-synagiosis 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.
Prognosis
The natural history of this disorder is not well known. The long term outlook for patients with treated moyamoya seems to be good. While symptoms may seem to improve almost immediately after the in-direct EDAS, EMS, and multiple burr holes surgeries, it will take probably 6–12 months before new vessels (blood supply) can develop sufficiently. With the direct STA-MCA surgery, increased blood supply is immediate.Once major strokes or bleeding take place, even with treatment, the patient may be left with permanent loss of function so it is very important to treat this condition promptly.
External links
- http://www.moyamoya.com
- http://www.childrenshospital.org/moyamoya
- http://moyamoyainfo.blogspot.com/
- http://moyamoya.stanford.edu
- http://www.mir.wustl.edu/research/internal.asp?NavID=707
- http://www.moyamoya.net
- http://www.kispi.uzh.ch/Kinderspital/Chirurgie/Chirurgie-1/Neurochirurgie/Moyamoya_en.html
- http://www.krupp-krankenhaus.de/fileadmin/Bilddatenbank/Bilddatenbank_Kliniken_Abteilungen/Neurologie/Patienteninfo-Neurologie-Moyamoya-2010-03-15.pdf