Moya Moya Disease

Moyamoya Disease/Syndrome

Mabel Lopez, Ph.D.

I. Overview.  Moyamoya Disease was first described in Japanese children in the 1960s1, but has since been diagnosed in all races and in adults. However, it more commonly seen in Japanese (90%), is rare in Caucasians, and has a peak incidence in childhood (50% <10 yrs. old, 76% < 20 yrs. old).2-3 Moreover, it is more common in females than in males (4:1) and 7% of the cases are familial.3

III. Diagnosis.  Neuroanatomically, this disease is characterized by stenosis (narrowing) or occlusion of the supraclinoid (distal) ICA (internal carotid artery), the proximal MCA (middle cerebral artery) and ACA (anterior cerebral arteries), and less commonly the proximal PCA (posterior cerebral artereries). This occlusion results in a network of dilated collateral vessels, usually lenticulostriate and thalamoperforating arteries, that on angiography have a vascular blush resembling a puff of smoke, or moyamoya” in Japanese (Figure 1). Involvement is usually bilateral. For a definite diagnosis of moyamoya disease, arteriography has been traditionally regarded as necessary. It should be noted that arteriography is not without risk and carries an appreciable morbidity and mortality, particularly when performed on acutely ill patients.  The CT appearances of moyamoya disease are nonspecific and include the presence of cerebral cortical atrophy (commonly in the frontal lobes), multiple infarcts, and intracranial hemorrhage. When MRI is compared to arteriography, the diagnosis of moyamoya can be made with MRI on all angiographically definite cases and information can be inferred in angiographically probable cases; a correlation of up to 80% has been reported between MRI and angiographic findings. Currently, the literature is pressing for the use of MRI as a safe, noninvasive imaging alternative to arteriography.2

IV. Aetiology.   The aetiology of the disease remains unknown. However, the disease has been associated with a history of tonsillitis, sinusitis, otitis media, neurofibromatosis (genetic disease), peri-arteris nodosa (projections around the arteries), atherosclerosis, sickle cell disease, Down’s syndrome, tuberous sclerosis, Fanconi’s anemia (rare, inherited type of aplastic anemia which carries an increased risk to the patient of developing leukemia), or basal meningitis, including tuberculous and leptospriral meningitis.2 The disease is progressive, and the clinical course is ultimately determined by the effectiveness of the collateral circulation. The literature suggests that “moyamoya disease” be used when the cause is idiopathic, whereas the term “moyamoya syndrome” is reserved for cases where the underlying condition is known.2

V. Sequelae. The disease generally presents as cerebral ischemia (more common in children) or subarachnoid hemorrhage (more common in adults), usually followed by hemiparesis (most common), facial palsy, nystagmus (rapid, involuntary eye movements), aphasia, dysarthria (imperfect articulation of speech), pseudobulbar palsy, involuntary movements, and convulsions. Unusual manifestations, including epilepsy and peripheral vascular occlusions have been described. Deterioration of IQ is usually found, and is sometimes a progressive feature of the disease. Autopsy findings are usually limited to death in the fifth and sixth decades of life, presumably at the end-stage of the disease. Autopsy findings are consistent with those of imaging: localized occlusion of the supraclinoid portion of the ICA extends to the proximal ACA and MCA, involvement of PCA is uncommon. Histological findings have revealed fibrocellular thickening, with hyperplasia of the intima (i.e., increased number of normal cells in inner layer of blood vessels).

VI. Treatment.  There is no cure for moyamoya disease. Treatment is symptomatic and supportive. For example, individual’s experiencing transient ischemic attacks and stroke may be given aspirin, vasodilators, or anticoagulants to reduce the risk of future attacks.  Revasulation may also be an option in order to restore blood supply; children respond better to surgery than adults. There are many operations that have been developed for the condition, but currently the most favored are: EDAS, EMS, STA-MCA and multiple burr holes.  The EDAS (encephaloduroarteriosynangiosis) procedure requires dissecting 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) operation, 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. Other operations include: the STA-MCA (superficial temporal artery-middle cerebral artery) in which a scalp artery is directly sutured to a brain surface artery; and a procedure in which multiple small holes (burr holes) are placed in the skull to allow for growth of new vessels into the brain from the scalp. While symptoms may seem to improve almost immediately after surgery, it will take probably 6-12 months before new vessels can develop sufficiently. Once major strokes or bleeding take place, even with treatment the child may be left with permanent loss of function so it is very important to treat this condition promptly.5

References:
1.      Nishimoto A. & Takeuchi S. (1968). Abnormal cerebrovascualr network related to internal carotid artery disease. Journal of Neurosurgery, 29, 223-30. Cited in 2
2.      Farrugia, M., Howlett, DC, & Saks, A.M. (1996). Moyamoya disease. Postgraduate Medical Journal, 73 (863), 549-52.
3.      Levin, S. (1982). Moyamoya disease.  Developmental Medical Child Neurology, 24, 850-59.
4.      Gordon, N., & Isler, W. (1989). Childhood moyamoya disease.  Developmental Medical Child Neurology, 31, 98-107.
Ueki, K. Meyer, F.B., & Mellinger, J.F. (1994). Moyamoya disease: The disorder and surgical treatment. Mayo Clinical Proceedings, 69, 749-57.

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