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Moyamoya Disease: A noninflammatory, progressive occlusion of the intracranial CAROTID ARTERIES and the formation of netlike collateral arteries arising from the CIRCLE OF WILLIS. Cerebral angiogram shows the puff-of-smoke (moyamoya) collaterals at the base of the brain. It is characterized by endothelial HYPERPLASIA and FIBROSIS with thickening of arterial walls. This disease primarily affects children but can also occur in adults.Cerebral Revascularization: Microsurgical revascularization to improve intracranial circulation. It usually involves joining the extracranial circulation to the intracranial circulation but may include extracranial revascularization (e.g., subclavian-vertebral artery bypass, subclavian-external carotid artery bypass). It is performed by joining two arteries (direct anastomosis or use of graft) or by free autologous transplantation of highly vascularized tissue to the surface of the brain.Cerebral Angiography: Radiography of the vascular system of the brain after injection of a contrast medium.Meningeal Arteries: Arteries which supply the dura mater.Temporal Arteries: Arteries arising from the external carotid or the maxillary artery and distributing to the temporal region.Cerebral Arteries: The arterial blood vessels supplying the CEREBRUM.Magnetic Resonance Angiography: Non-invasive method of vascular imaging and determination of internal anatomy without injection of contrast media or radiation exposure. The technique is used especially in CEREBRAL ANGIOGRAPHY as well as for studies of other vascular structures.Meninges: The three membranes that cover the BRAIN and the SPINAL CORD. They are the dura mater, the arachnoid, and the pia mater.Carotid Artery, Internal: Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose.Cerebral Hemorrhage: Bleeding into one or both CEREBRAL HEMISPHERES including the BASAL GANGLIA and the CEREBRAL CORTEX. It is often associated with HYPERTENSION and CRANIOCEREBRAL TRAUMA.Cerebrovascular Circulation: The circulation of blood through the BLOOD VESSELS of the BRAIN.Tomography, Emission-Computed, Single-Photon: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.Middle Cerebral Artery: The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the CEREBRAL CORTEX. These are the areas involved in motor, sensory, and speech activities.Circle of Willis: A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.Posterior Cerebral Artery: Artery formed by the bifurcation of the BASILAR ARTERY. Branches of the posterior cerebral artery supply portions of the OCCIPITAL LOBE; PARIETAL LOBE; inferior temporal gyrus, brainstem, and CHOROID PLEXUS.Photophobia: Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.Arterial Occlusive Diseases: Pathological processes which result in the partial or complete obstruction of ARTERIES. They are characterized by greatly reduced or absence of blood flow through these vessels. They are also known as arterial insufficiency.Collateral Circulation: Maintenance of blood flow to an organ despite obstruction of a principal vessel. Blood flow is maintained through small vessels.Anastomosis, Surgical: Surgical union or shunt between ducts, tubes or vessels. It may be end-to-end, end-to-side, side-to-end, or side-to-side.Ischemic Attack, Transient: Brief reversible episodes of focal, nonconvulsive ischemic dysfunction of the brain having a duration of less than 24 hours, and usually less than one hour, caused by transient thrombotic or embolic blood vessel occlusion or stenosis. Events may be classified by arterial distribution, temporal pattern, or etiology (e.g., embolic vs. thrombotic). (From Adams et al., Principles of Neurology, 6th ed, pp814-6)Cerebral Infarction: The formation of an area of NECROSIS in the CEREBRUM caused by an insufficiency of arterial or venous blood flow. Infarcts of the cerebrum are generally classified by hemisphere (i.e., left vs. right), lobe (e.g., frontal lobe infarction), arterial distribution (e.g., INFARCTION, ANTERIOR CEREBRAL ARTERY), and etiology (e.g., embolic infarction).Intracranial Hemorrhages: Bleeding within the SKULL, including hemorrhages in the brain and the three membranes of MENINGES. The escape of blood often leads to the formation of HEMATOMA in the cranial epidural, subdural, and subarachnoid spaces.Angiography, Digital Subtraction: A method of delineating blood vessels by subtracting a tissue background image from an image of tissue plus intravascular contrast material that attenuates the X-ray photons. The background image is determined from a digitized image taken a few moments before injection of the contrast material. The resulting angiogram is a high-contrast image of the vessel. This subtraction technique allows extraction of a high-intensity signal from the superimposed background information. The image is thus the result of the differential absorption of X-rays by different tissues.Neurosurgical Procedures: Surgery performed on the nervous system or its parts.Carotid Artery, External: Branch of the common carotid artery which supplies the exterior of the head, the face, and the greater part of the neck.