According to Suzukis system, it can be classified into six stages:
Stage 1 Narrowing of carotid fork
Stage 2 Initiation of the moyamoya and dilatation of intracranial main arteries
Stage 3 Intensification of the moyamoya and defects of the anterior cerebral artery and middle cerebral artery
Stage 4 Minimization of the moyamoya and defects of the posterior cerebral artery
Stage 5 Reduction of the moyamoya and development of external carotid artery collaterals
Stage 6 Disappearance of the moyamoya and circulation only via external cerebral artery and vertebral arteryMagnetic resonance angiography (MRA) is also useful in diagnosing the disease with good correlation with Suzukis grading system.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.
In atherosclerosis, the walls of arteries are damaged, leading to the deposition of fat and immune cells, and ultimately the accumulation of immune cells laden with fat. In moyamoya, the inner layer of the carotid artery proliferates within the arterial lumen. The artery also fills with blood clots, which may cause strokes.Moyamoya disease tends to affect adults in the third to fourth decade of life. In children it tends to cause strokes or seizures. In adults it tends to cause strokes or bleeding. 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
Cerebral angiography is the gold standard of diagnosing moyamoya disease and its progression.