Abstract
This article is a clinical review of Moyamoya disease (MMD) and Moyamoya syndrome (MMS). We review the incidence, epidemiology, pathology, historical context, clinical and radiographic findings, diagnostic imaging modalities, radiographic grading systems, the effectiveness of medical, interventional, and surgical treatment, and some of the nuances of surgical treatment options. This article will help pediatricians, neurologists, neurosurgeons, and other clinical practitioners who are involved in caring for patients with this rare clinical entity.MMD is an intrinsic primary disease process that causes bilateral progressive stenosis of the anterior intracranial circulation with the involvement of the proximal portions of the intracranial internal carotid artery (ICA) extending to involve the proximal portions of the anterior cerebral artery (ACA) and middle cerebral artery (MCA); posterior circulation involvement is very rare. This causes a compensatory response where large numbers of smaller vessels such as the lenticulostriate arteries begin to enlarge and proliferate, which gives the angiographic appearance of a "Puff of Smoke", which is translated into Japanese as "Moyamoya”. MMS is a secondary process that occurs in response to another underlying pathological process that causes stenosis of intracranial blood vessels, such as radiation. For example, an external source of radiation causes stenosis of the ICA with a compensatory response of smaller blood vessels, which then enlarge and proliferate in response and has the same "Puff of Smoke" appearance on the diagnostic cerebral angiogram (DCA).Histological findings include an irregular internal elastic lamina with luminal narrowing, hyperplasia of the tunica media, and intimal thickening with vacuolar degeneration in smooth muscle cells in the tunica media. Compensation for diminishing blood supply occurs through angiogenesis, which causes the proliferation and enlargement of smaller collateral blood vessels to increase blood supply to under-perfused areas of the brain.MMD is rare in the United States, with just 0.086 newly diagnosed cases per 100,000 individuals per year, which is approximately one per million new cases annually. Risk factors for MMD include Eastern Asian ancestry and predisposing conditions such as neurofibromatosis and Down's syndrome.Clinically, patients often present with stroke signs and symptoms from cerebral ischemia. The proliferation of collateral blood vessels within the basal ganglia can produce movement disorders. Catheter-based DCA is the current gold standard for obtaining a diagnosis. CT perfusion allows preoperative identification of ischemic vascular territories, which may be amenable to surgical intervention. MRI enables rapid detection of acute ischemic stroke using diffusion-weighted Imaging (DWI) and apparent diffusion coefficient (ADC) sequences to assess for any diffusion restriction. Non-contrast CT of the head is used to rule out acute hemorrhage in the presentation of a progressive neurological deficit.The treatment option for Moyamoya is generally surgical; medical treatment has failed to halt disease progression and neuro-interventional techniques such as attempted stenting of stenosed vessels have failed. Surgical options include direct and indirect cerebrovascular bypass.
Highlights
BackgroundMoyamoya disease (MMD) is a chronic cerebrovascular disorder characterized by a progressive narrowing of the intracranial portions of the distal internal carotid artery (ICA) and the initial proximal components of the middle cerebral artery (MCA) and anterior cerebral artery (ACA)
Epidemiology, pathology, historical context, clinical and radiographic findings, diagnostic imaging modalities, radiographic grading systems, the effectiveness of medical, interventional, and surgical treatment, and some of the nuances of surgical treatment options
Surgical treatment should strongly be considered for symptomatic patients to improve hemodynamic flow to physiologically under-perfused areas in the ICA, proximal MCA, and proximal ACA territory of brain parenchyma
Summary
Moyamoya disease (MMD) is a chronic cerebrovascular disorder characterized by a progressive narrowing of the intracranial portions of the distal internal carotid artery (ICA) and the initial proximal components of the middle cerebral artery (MCA) and anterior cerebral artery (ACA). The incident rate of occurrence of an ischemic event related to surgery is 2.7%, transient ischemic attack (TIA) is 7.3%, seizure activity is 5.4%, and hemorrhage is 4% with a wound infection rate of less than 1% [38] The advantage of this direct procedure is that it reestablishes blood flow immediately once the anastomosis is created. The temporalis muscle receives blood supply from the superficial deep temporal artery and from deep accessory temporal arteries beneath the muscle from proximal branches of the internal maxillary artery (IMA) It is less technically demanding when compared to a direct STA-to-MCA bypass procedure. It is common practice to have hyperdynamic therapy as immediate postoperative therapy to ensure the bypass graft remains patent with intravenous fluids running at 1.5 times the maintenance rate
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