Medical terms (alphabetically arranged) Anastomosis There are two surgical anastomoses in the management of moyamoya disease. Direct anastomosis means that the superficial temporal artery (extracranial artery) is surgically anastomosed with the small cortical branch of the middle cerebral artery (intracranial artery). Indirect anastomosis means that muscles, fascias, and/or dura mater (the membrane which covers the brain) are surgically placed over the cortical surface. Anterior cerebral artery (ACA) Intracranial internal carotid artery gives rise to anterior and middle cerebral arteries. Anterior cerebral artery courses in the midline and supplies medial aspects of the frontal lobes and corpus callosum. This vessel is usually not the recipient artery of bypass surgery. When moyamoya disease advances, the territory of the anterior cerebral artery becomes ischemic, presenting the weakness of the contralateral leg. Basal ganglia Gray matter located at the base of the brain, being supplied by perforating arteries from the circle of Willis. In moyamoya disease, these perforating arteries enlarge due to the demand of the brain. In MR images, the enlarged perforating arteries are visualized as flow void (signal void) in the basal ganglia. Cerebral blood flow (CBF) measurement Vascular anatomy is studied by angiography. Stenosis or occlusion does not always mean cerebral ischemia. Thus, cerebral blood flow measurement is required to assess the real blood flow supplying the brain. In cerebral ischemia, small arteries in the brain may enlarge reactively to the demand. The degree of this reactive vaso-dilation is assessed by diamox loading which causes pharmacological vasodilation. SPECT (single photon emission computed tomography) and PET (positron emission tomography) are used for measurement of the cerebral blood flow. Pre- and post-operative CBF measurements are usually performed in the management of moyamoya disease. Cerebral catheter angiography In catheter cerebral angiography, small tube called catheter is inserted in most cases into the femoral artery under local (or occasionally under general) anesthesia. Using iodine contrast material, vasculature in the brain is visualized. In moyamoya disease, stenosis of the renal arteries is occasionally observed. Thus, we usually obtain renal angiograms when cerebral angiography is performed. Depend upon the institutions, the catheter is inserted into the brachial artery. Cerebral catheter angiography is fairy safe, but it is not 100% safe. Complications related to catheter angiography include cerebral embolism, allergy to iodine, hematoma at the arterial puncture site, etc. In moyamoya disease, hyperventilation and/or crying may cause brain ischemia, resulting in brain infarction. Circle of Willis Willis is the name of the old anatomist. Blood flow to the brain is supplied by two internal carotid arteries and two vertebral arteries, which are located bilaterally. These four arteries form the vascular circle at the base of the brain (the circle of Willis). When one of the arteries becomes occlusive, the rest of the three vessels help to supply blood flow to the brain. Encephalo-duro-arterio-synangiosis (EDAS) A kind of indirect anastomosis. Dural mater and its attached dural arteries are surgically put over the brain surface. It is believed that this indirect anastomosis becomes effective later than direct one. Encephalo-myo-synangiosis (EMS) A kind of indirect anastomosis. Temporal muscle and its membrane are surgically put over the brain surface. It is believed that this indirect anastomosis becomes effective later than direct one. Hyperventilation Hyperventilation may cause brain ischaemia because the cerebral arteries become stenotic (spastic) due to reduced CO2 concentration. This hyperventilation may occur when the patient plays flute and crying loud. Ischemic symptoms include hemiparesis, seizure, involuntary movement, consciousness disturbance, sensory disturbance, speech disturbance, etc. Internal carotid artery (ICA) In the cervical portion, the common carotid artery divides to external and internal carotid arteries. The latter runs intracranially. In moyamoya disease, the terminal portion of the internal carotid artery becomes stenotic or occlusive. Bilateral internal carotid arteries and bilateral vertebral arteries form the arterial circle of the Willis at the base of the brain. Magnetic resonance angiography (MRA) Using magnetic resonance imaging technology, non-invasive visualization of the cerebral vessels (arteries and veins) is possible. This is a safe method without irradiation of x-ray, but its image quality is more or less inferior to that obtained by catheter angiography. Magnetic resonance imaging (MRI) Brain image is obtained from the spatial and biological information of the protons in the brain. Contrary to the x-ray computed tomography, MRI does not require ionizing radiation, which means no radiation effects to the body including brain. Image quality depends largely upon the strength of the magnet field. For imaging of moyamoya disease, high field (strong magnet) MR scanner provides better image quality. This means that you should be scanned with MR scanner operating at 1.0 or 1.5 tesla. Magnetic resonance angiography (MRA) is imaging method to visualize intracranial vessels using MRI. Middle cerebral artery (MCA) T his is a branch of the intracranial internal carotid artery. The large part of the cerebral hemisphere is supplied by this vessel. Bypass surgery uses this artery anastomosing with the superficial temporal artery. Moyamoya vessel Moyamoya vessels are perforating arteries at the base of the brain which enlarge due to the demand of the brain. Angiographic appearance of these moyamoya vessels resemble the puff of the cigarette smoke. In Japanese language, hazy appearance is called "moyamoya." Quasi-moyamoya disease When the angiographic findings are same to those of moyamoya disease, but the associated systemic disease is accompanied (exclusion criteria of moyamoya disease), it is called quasi- or akin-moyamoya disease. Superficial temporal artery (STA) This artery runs superficially and supplies the scalp. You can palpate this vessel in front of the tragus of the ear. This artery gives rise to frontal and parietal branches. Using both branches, double anastomoses or using the parietal branch, single anastomosis may be performed. Superficial temporal artery - middle cerebral artery anastomosis (STA-MCA anastomosis) Contrary to indirect anastomosis, this direct anastomosis becomes effective early. Thus, if urgent treatment is required, direct anastomosis is indicated. Vertebral arteryTogether with the internal carotid arteries, vertebral arteries carry the blood to the brain. This artery run in the the cervical vertebral bones. Two vertebral arteries form the basilar artery in the brain. Principally, steno-occlusive changes do not occur in the basilar artery.