烟雾病图文课件_3

Moyamoya Disease Content Definition Etiology Pathophysiology Clinical Manifestation Diagnosis Treatment Prognosis Definition 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 tohemorrhage, aneurysm and thrombosis. On conventional X-ray angiography, these collateral vessels have the appearance of a “puff of smoke“ (described as “ (moyamoya)“ in Japanese) Etiology About 10% of cases of moyamoya disease are familial, and some cases result from specific genetic mutations. In Japan the overall incidence is higher (0.35 per 100,000). 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 C resistance, 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. Pathophysiology The disease moyamoya makes the blood leak out of the arteries, causing pressure to the brain and subsequent headaches. The pathogenesis of moyamoya disease is unknown, although the gene ring finger protein 213 (RNF213) has been implicated. Once it begins, the vascular occlusion tends to continue despite any known medical management. In some people this leads to transient ischemic attacks or repeated strokes with severe functional impairment or even death. In others, the blockage may not cause any symptoms. The disease causes constrictions primarily in the internal carotid artery, and often extends to the middle and anterior cerebral arteries, branches of the internal carotid artery inside the skull. 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, arising from the basilar artery. Clinical Manifestation The clinical features are strokes, recurrent transient ischemic attacks (TIAs), sensorimotor paralysis (numbness and paralysis of the extremities), convulsions and/or migraine-like headaches. Moreover, following a stroke, secondary bleeding may occur. Such bleeding, called hemorrhagic strokes, may also stem from rupture of the weak neovascular vessel walls. Diagnosis The diagnosis of moyamoya is suggested by CT, MRI, or angiogram results. Often nuclear medicine studies such as SPECT 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 Drugs such as antiplatelet agents (including aspirin) are usually given to prevent clots, but surgery is usually recommended. 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. Prognosis The long term outlook for patients with treated moyamoya seems to be good. It will take probably 612 months before new vessels can develop to give a sufficient blood supply. Onc