Fenestration, Labyrinth: The surgical creation of a new opening in the labyrinth of the ear for the restoration of hearing in cases of OTOSCLEROSIS. (Dorland, 27th ed)Vestibule, Labyrinth: An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony COCHLEA anteriorly, and SEMICIRCULAR CANALS posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the STAPES of the MIDDLE EAR.Labyrinth Diseases: Pathological processes of the inner ear (LABYRINTH) which contains the essential apparatus of hearing (COCHLEA) and balance (SEMICIRCULAR CANALS).Ear, Inner: The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. The bony labyrinth is a complex of three interconnecting cavities or spaces (COCHLEA; VESTIBULAR LABYRINTH; and SEMICIRCULAR CANALS) in the TEMPORAL BONE. Within the bony labyrinth lies the membranous labyrinth which is a complex of sacs and tubules (COCHLEAR DUCT; SACCULE AND UTRICLE; and SEMICIRCULAR DUCTS) forming a continuous space enclosed by EPITHELIUM and connective tissue. These spaces are filled with LABYRINTHINE FLUIDS of various compositions.Fontan Procedure: A procedure in which total right atrial or total caval blood flow is channeled directly into the pulmonary artery or into a small right ventricle that serves only as a conduit. The principal congenital malformations for which this operation is useful are TRICUSPID ATRESIA and single ventricle with pulmonary stenosis.Semicircular Canals: Three long canals (anterior, posterior, and lateral) of the bony labyrinth. They are set at right angles to each other and are situated posterosuperior to the vestibule of the bony labyrinth (VESTIBULAR LABYRINTH). The semicircular canals have five openings into the vestibule with one shared by the anterior and the posterior canals. Within the canals are the SEMICIRCULAR DUCTS.Placenta: A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (CHORIONIC VILLI) derived from TROPHOBLASTS and a maternal portion (DECIDUA) derived from the uterine ENDOMETRIUM. The placenta produces an array of steroid, protein and peptide hormones (PLACENTAL HORMONES).Placentation: The development of the PLACENTA, a highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products between mother and FETUS. The process begins at FERTILIZATION, through the development of CYTOTROPHOBLASTS and SYNCYTIOTROPHOBLASTS, the formation of CHORIONIC VILLI, to the progressive increase in BLOOD VESSELS to support the growing fetus.Cysts: Any fluid-filled closed cavity or sac that is lined by an EPITHELIUM. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues.Endolymphatic Duct: The part of the membranous labyrinth that traverses the bony vestibular aqueduct and emerges through the bone of posterior cranial fossa (CRANIAL FOSSA, POSTERIOR) where it expands into a blind pouch called the endolymphatic sac.Arachnoid Cysts: Intracranial or spinal cavities containing a cerebrospinal-like fluid, the wall of which is composed of arachnoidal cells. They are most often developmental or related to trauma. Intracranial arachnoid cysts usually occur adjacent to arachnoidal cistern and may present with HYDROCEPHALUS; HEADACHE; SEIZURES; and focal neurologic signs. (From Joynt, Clinical Neurology, 1994, Ch44, pp105-115)Ventriculostomy: Surgical creation of an opening in a cerebral ventricle.Vestibular Diseases: Pathological processes of the VESTIBULAR LABYRINTH which contains part of the balancing apparatus. Patients with vestibular diseases show instability and are at risk of frequent falls.Vestibular Nucleus, Lateral: Vestibular nucleus lying immediately superior to the inferior vestibular nucleus and composed of large multipolar nerve cells. Its upper end becomes continuous with the superior vestibular nucleus.Vestibular Nuclei: The four cellular masses in the floor of the fourth ventricle giving rise to a widely dispersed special sensory system. Included is the superior, medial, inferior, and LATERAL VESTIBULAR NUCLEUS. (From Dorland, 27th ed)Petrous Bone: The dense rock-like part of temporal bone that contains the INNER EAR. Petrous bone is located at the base of the skull. Sometimes it is combined with the MASTOID PROCESS and called petromastoid part of temporal bone.Caloric Tests: Elicitation of a rotatory nystagmus by stimulating the semicircular canals with water or air which is above or below body temperature. In warm caloric stimulation a rotatory nystagmus is developed toward the side of the stimulated ear; in cold, away from the stimulated side. Absence of nystagmus indicates the labyrinth is not functioning.Vestibular Nerve: The vestibular part of the 8th cranial nerve (VESTIBULOCOCHLEAR NERVE). The vestibular nerve fibers arise from neurons of Scarpa's ganglion and project peripherally to vestibular hair cells and centrally to the VESTIBULAR NUCLEI of the BRAIN STEM. These fibers mediate the sense of balance and head position.Anterior Cerebral Artery: Artery formed by the bifurcation of the internal carotid artery (CAROTID ARTERY, INTERNAL). Branches of the anterior cerebral artery supply the CAUDATE NUCLEUS; INTERNAL CAPSULE; PUTAMEN; SEPTAL NUCLEI; GYRUS CINGULI; and surfaces of the FRONTAL LOBE and PARIETAL LOBE.Endolymphatic Sac: The blind pouch at the end of the endolymphatic duct. It is a storage reservoir for excess ENDOLYMPH, formed by the blood vessels in the membranous labyrinth.Trophoblasts: Cells lining the outside of the BLASTOCYST. After binding to the ENDOMETRIUM, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (PLACENTA).Hydrocharitaceae: A plant family of the order Hydrocharitales, subclass ALISMATIDAE, class Liliopsida (monocotyledons).Neuroendoscopy: PROCEDURES that use NEUROENDOSCOPES for disease diagnosis and treatment. Neuroendoscopy, generally an integration of the neuroendoscope with a computer-assisted NEURONAVIGATION system, provides guidance in NEUROSURGICAL PROCEDURES.Aortography: Radiographic visualization of the aorta and its branches by injection of contrast media, using percutaneous puncture or catheterization procedures.Intracranial Aneurysm: Abnormal outpouching in the wall of intracranial blood vessels. Most common are the saccular (berry) aneurysms located at branch points in CIRCLE OF WILLIS at the base of the brain. Vessel rupture results in SUBARACHNOID HEMORRHAGE or INTRACRANIAL HEMORRHAGES. Giant aneurysms (>2.5 cm in diameter) may compress adjacent structures, including the OCULOMOTOR NERVE. (From Adams et al., Principles of Neurology, 6th ed, p841)Cochlea: The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH.Heart Bypass, Right: Diversion of the flow of blood from the entrance to the right atrium directly to the pulmonary arteries, avoiding the right atrium and right ventricle (Dorland, 28th ed). This a permanent procedure often performed to bypass a congenitally deformed right atrium or right ventricle.Tenotomy: Surgical division of a tendon for relief of a deformity that is caused by congenital or acquired shortening of a muscle (Stedman, 27th ed). Tenotomy is performed in order to lengthen a muscle that has developed improperly, or become shortened and is resistant to stretching.Tarlov Cysts: Perineurial cysts commonly found in the SACRAL REGION. They arise from the PERINEURIUM membrane within the SPINAL NERVE ROOTS. The distinctive feature of the cysts is the presence of spinal nerve root fibers within the cyst wall, or the cyst cavity itself.Aneurysm, Dissecting: Aneurysm caused by a tear in the TUNICA INTIMA of a blood vessel leading to interstitial HEMORRHAGE, and splitting (dissecting) of the vessel wall, often involving the AORTA. Dissection between the intima and media causes luminal occlusion. Dissection at the media, or between the media and the outer adventitia causes aneurismal dilation.Otosclerosis: Formation of spongy bone in the labyrinth capsule which can progress toward the STAPES (stapedial fixation) or anteriorly toward the COCHLEA leading to conductive, sensorineural, or mixed HEARING LOSS. Several genes are associated with familial otosclerosis with varied clinical signs.Apicoectomy: Excision of the apical portion of a tooth through an opening made in the overlying labial, buccal, or palatal alveolar bone. (Dorland, 28th ed)Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Rotation: Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Endolymph: The lymph fluid found in the membranous labyrinth of the ear. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Cerebral Angiography: Radiography of the vascular system of the brain after injection of a contrast medium.Embryo Loss: Early pregnancy loss during the EMBRYO, MAMMALIAN stage of development. In the human, this period comprises the second through eighth week after fertilization.Reflex, Vestibulo-Ocular: A reflex wherein impulses are conveyed from the cupulas of the SEMICIRCULAR CANALS and from the OTOLITHIC MEMBRANE of the SACCULE AND UTRICLE via the VESTIBULAR NUCLEI of the BRAIN STEM and the median longitudinal fasciculus to the OCULOMOTOR NERVE nuclei. It functions to maintain a stable retinal image during head rotation by generating appropriate compensatory EYE MOVEMENTS.Cochlear Diseases: Pathological processes of the snail-like structure (COCHLEA) of the inner ear (LABYRINTH) which can involve its nervous tissue, blood vessels, or fluid (ENDOLYMPH).Cell Membrane Structures: Structures which are part of the CELL MEMBRANE or have cell membrane as a major part of their structure.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Labyrinthitis: Inflammation of the inner ear (LABYRINTH).Vertigo: An illusion of movement, either of the external world revolving around the individual or of the individual revolving in space. Vertigo may be associated with disorders of the inner ear (EAR, INNER); VESTIBULAR NERVE; BRAINSTEM; or CEREBRAL CORTEX. Lesions in the TEMPORAL LOBE and PARIETAL LOBE may be associated with FOCAL SEIZURES that may feature vertigo as an ictal manifestation. (From Adams et al., Principles of Neurology, 6th ed, pp300-1)Ultrasonic Surgical Procedures: The use of HIGH-ENERGY SHOCK WAVES, in the frequency range of 20-60 kHz, to cut through or remove tissue. The tissue fragmentation by ultrasonic surgical instruments is caused by mechanical effects not heat as with HIGH-INTENSITY FOCUSED ULTRASOUND ABLATION.Spiral Ligament of Cochlea: A spiral thickening of the fibrous lining of the cochlear wall. Spiral ligament secures the membranous COCHLEAR DUCT to the bony spiral canal of the COCHLEA. Its spiral ligament fibrocytes function in conjunction with the STRIA VASCULARIS to mediate cochlear ion homeostasis.Heart Defects, Congenital: Developmental abnormalities involving structures of the heart. These defects are present at birth but may be discovered later in life.Endolymphatic Hydrops: An accumulation of ENDOLYMPH in the inner ear (LABYRINTH) leading to buildup of pressure and distortion of intralabyrinthine structures, such as COCHLEA and SEMICIRCULAR CANALS. It is characterized by SENSORINEURAL HEARING LOSS; TINNITUS; and sometimes VERTIGO.Capillaries: The minute vessels that connect the arterioles and venules.Scandentia: An order of the class MAMMALS that consists of one family, TUPAIIDAE (tree shrews), 5 genera (one of which is TUPAIA), and 16 species. Their recent distribution is from India to the Philippines, southern China to Java, Borneo, Sumatra, Bali, and other islands in those regions.Cerebral Arteries: The arterial blood vessels supplying the CEREBRUM.Aortic Aneurysm, Thoracic: An abnormal balloon- or sac-like dilatation in the wall of the THORACIC AORTA. This proximal descending portion of aorta gives rise to the visceral and the parietal branches above the aortic hiatus at the diaphragm.Imaging, Three-Dimensional: The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.Blood Vessel Prosthesis Implantation: Surgical insertion of BLOOD VESSEL PROSTHESES to repair injured or diseased blood vessels.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Prosthesis Design: The plan and delineation of prostheses in general or a specific prosthesis.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Vestibular Function Tests: A number of tests used to determine if the brain or balance portion of the inner ear are causing dizziness.Septum Pellucidum: A triangular double membrane separating the anterior horns of the LATERAL VENTRICLES of the brain. It is situated in the median plane and bounded by the CORPUS CALLOSUM and the body and columns of the FORNIX (BRAIN).Hydrocephalus: Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, INTRACRANIAL HYPERTENSION; HEADACHE; lethargy; URINARY INCONTINENCE; and ATAXIA.Aortic Aneurysm: An abnormal balloon- or sac-like dilatation in the wall of AORTA.Blood Vessel Prosthesis: Device constructed of either synthetic or biological material that is used for the repair of injured or diseased blood vessels.Endovascular Procedures: Minimally invasive procedures, diagnostic or therapeutic, performed within the BLOOD VESSELS. They may be perfomed via ANGIOSCOPY; INTERVENTIONAL MAGNETIC RESONANCE IMAGING; INTERVENTIONAL RADIOGRAPHY; or INTERVENTIONAL ULTRASONOGRAPHY.Cochlear Duct: A spiral tube that is firmly suspended in the bony shell-shaped part of the cochlea. This ENDOLYMPH-filled cochlear duct begins at the vestibule and makes 2.5 turns around a core of spongy bone (the modiolus) thus dividing the PERILYMPH-filled spiral canal into two channels, the SCALA VESTIBULI and the SCALA TYMPANI.Metrial Gland: Collection of granular epithelial cells in the uterine muscle beneath the placenta that develop during pregnancy in certain species of animals.Aortic Aneurysm, Abdominal: An abnormal balloon- or sac-like dilatation in the wall of the ABDOMINAL AORTA which gives rise to the visceral, the parietal, and the terminal (iliac) branches below the aortic hiatus at the diaphragm.Jaw DiseasesVestibulocochlear Nerve Diseases: Pathological processes of the VESTIBULOCOCHLEAR NERVE, including the branches of COCHLEAR NERVE and VESTIBULAR NERVE. Common examples are VESTIBULAR NEURITIS, cochlear neuritis, and ACOUSTIC NEUROMA. Clinical signs are varying degree of HEARING LOSS; VERTIGO; and TINNITUS.Microsurgery: The performance of surgical procedures with the aid of a microscope.Medical Illustration: The field which deals with illustrative clarification of biomedical concepts, as in the use of diagrams and drawings. The illustration may be produced by hand, photography, computer, or other electronic or mechanical methods.Meniere Disease: A disease of the inner ear (LABYRINTH) that is characterized by fluctuating SENSORINEURAL HEARING LOSS; TINNITUS; episodic VERTIGO; and aural fullness. It is the most common form of endolymphatic hydrops.Pregnancy, Animal: The process of bearing developing young (EMBRYOS or FETUSES) in utero in non-human mammals, beginning from FERTILIZATION to BIRTH.Endoscopy: Procedures of applying ENDOSCOPES for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. transluminal, to examine or perform surgery on the interior parts of the body.Pseudotumor Cerebri: A condition marked by raised intracranial pressure and characterized clinically by HEADACHES; NAUSEA; PAPILLEDEMA, peripheral constriction of the visual fields, transient visual obscurations, and pulsatile TINNITUS. OBESITY is frequently associated with this condition, which primarily affects women between 20 and 44 years of age. Chronic PAPILLEDEMA may lead to optic nerve injury (see OPTIC NERVE DISEASES) and visual loss (see BLINDNESS).Vertebral Artery: The first branch of the SUBCLAVIAN ARTERY with distribution to muscles of the NECK; VERTEBRAE; SPINAL CORD; CEREBELLUM; and interior of the CEREBRUM.Otolithic Membrane: A gelatinous membrane overlying the acoustic maculae of SACCULE AND UTRICLE. It contains minute crystalline particles (otoliths) of CALCIUM CARBONATE and protein on its outer surface. In response to head movement, the otoliths shift causing distortion of the vestibular hair cells which transduce nerve signals to the BRAIN for interpretation of equilibrium.Protein-Losing Enteropathies: Pathological conditions in the INTESTINES that are characterized by the gastrointestinal loss of serum proteins, including SERUM ALBUMIN; IMMUNOGLOBULINS; and at times LYMPHOCYTES. Severe condition can result in HYPOGAMMAGLOBULINEMIA or LYMPHOPENIA. Protein-losing enteropathies are associated with a number of diseases including INTESTINAL LYMPHANGIECTASIS; WHIPPLE'S DISEASE; and NEOPLASMS of the SMALL INTESTINE.Micromanipulation: The performance of dissections, injections, surgery, etc., by the use of micromanipulators (attachments to a microscope) that manipulate tiny instruments.Fetal Weight: The weight of the FETUS in utero. It is usually estimated by various formulas based on measurements made during PRENATAL ULTRASONOGRAPHY.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.Chinchilla: A genus of the family Chinchillidae which consists of three species: C. brevicaudata, C. lanigera, and C. villidera. They are used extensively in biomedical research.Vestibular Aqueduct: A small bony canal linking the vestibule of the inner ear to the posterior part of the internal surface of the petrous TEMPORAL BONE. It transmits the endolymphatic duct and two small blood vessels.Saccule and Utricle: Two membranous sacs within the vestibular labyrinth of the INNER EAR. The saccule communicates with COCHLEAR DUCT through the ductus reuniens, and communicates with utricle through the utriculosaccular duct from which the ENDOLYMPHATIC DUCT arises. The utricle and saccule have sensory areas (acoustic maculae) which are innervated by the VESTIBULAR NERVE.Curettage: A scraping, usually of the interior of a cavity or tract, for removal of new growth or other abnormal tissue, or to obtain material for tissue diagnosis. It is performed with a curet (curette), a spoon-shaped instrument designed for that purpose. (From Stedman, 25th ed & Dorland, 27th ed)Ketocholesterols: Cholesterol substituted in any position by a keto moiety. The 7-keto isomer inhibits 3-hydroxy-3-methylglutaryl-CoA reductase activity and inhibits cholesterol uptake in the coronary arteries and aorta in vitro.Nystagmus, Physiologic: Involuntary rhythmical movements of the eyes in the normal person. These can be naturally occurring as in end-position (end-point, end-stage, or deviational) nystagmus or induced by the optokinetic drum (NYSTAGMUS, OPTOKINETIC), caloric test, or a rotating chair.Cardiac Catheterization: Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.Neurosurgical Procedures: Surgery performed on the nervous system or its parts.Aneurysm, Ruptured: The tearing or bursting of the weakened wall of the aneurysmal sac, usually heralded by sudden worsening pain. The great danger of a ruptured aneurysm is the large amount of blood spilling into the surrounding tissues and cavities, causing HEMORRHAGIC SHOCK.Liver Diseases: Pathological processes of the LIVER.Pericardial Effusion: Fluid accumulation within the PERICARDIUM. Serous effusions are associated with pericardial diseases. Hemopericardium is associated with trauma. Lipid-containing effusion (chylopericardium) results from leakage of THORACIC DUCT. Severe cases can lead to CARDIAC TAMPONADE.Ear Neoplasms: Tumors or cancer of any part of the hearing and equilibrium system of the body (the EXTERNAL EAR, the MIDDLE EAR, and the INNER EAR).Basilar Artery: The artery formed by the union of the right and left vertebral arteries; it runs from the lower to the upper border of the pons, where it bifurcates into the two posterior cerebral arteries.Stents: Devices that provide support for tubular structures that are being anastomosed or for body cavities during skin grafting.Placental Lactogen: A polypeptide hormone of approximately 25 kDa that is produced by the SYNCYTIOTROPHOBLASTS of the PLACENTA, also known as chorionic somatomammotropin. It has both GROWTH HORMONE and PROLACTIN activities on growth, lactation, and luteal steroid production. In women, placental lactogen secretion begins soon after implantation and increases to 1 g or more a day in late pregnancy. Placental lactogen is also an insulin antagonist.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.Head Movements: Voluntary or involuntary motion of head that may be relative to or independent of body; includes animals and humans.Ventriculoperitoneal Shunt: Surgical creation of a communication between a cerebral ventricle and the peritoneum by means of a plastic tube to permit drainage of cerebrospinal fluid for relief of hydrocephalus. (From Dorland, 28th ed)Hair Cells, Vestibular: Sensory cells in the acoustic maculae with their apical STEREOCILIA embedded in a gelatinous OTOLITHIC MEMBRANE. These hair cells are stimulated by the movement of otolithic membrane, and impulses are transmitted via the VESTIBULAR NERVE to the BRAIN STEM. Hair cells in the saccule and those in the utricle sense linear acceleration in vertical and horizontal directions, respectively.Bone Conduction: Transmission of sound waves through vibration of bones in the SKULL to the inner ear (COCHLEA). By using bone conduction stimulation and by bypassing any OUTER EAR or MIDDLE EAR abnormalities, hearing thresholds of the cochlea can be determined. Bone conduction hearing differs from normal hearing which is based on air conduction stimulation via the EAR CANAL and the TYMPANIC MEMBRANE.Nystagmus, Pathologic: Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. (Adams et al., Principles of Neurology, 6th ed, p272)Yolk Sac: The first of four extra-embryonic membranes to form during EMBRYOGENESIS. In REPTILES and BIRDS, it arises from endoderm and mesoderm to incorporate the EGG YOLK into the DIGESTIVE TRACT for nourishing the embryo. In placental MAMMALS, its nutritional function is vestigial; however, it is the source of INTESTINAL MUCOSA; BLOOD CELLS; and GERM CELLS. It is sometimes called the vitelline sac, which should not be confused with the VITELLINE MEMBRANE of the egg.Vestibulocochlear Nerve: The 8th cranial nerve. The vestibulocochlear nerve has a cochlear part (COCHLEAR NERVE) which is concerned with hearing and a vestibular part (VESTIBULAR NERVE) which mediates the sense of balance and head position. The fibers of the cochlear nerve originate from neurons of the SPIRAL GANGLION and project to the cochlear nuclei (COCHLEAR NUCLEUS). The fibers of the vestibular nerve arise from neurons of Scarpa's ganglion and project to the VESTIBULAR NUCLEI.Hearing Loss, Sudden: Sensorineural hearing loss which develops suddenly over a period of hours or a few days. It varies in severity from mild to total deafness. Sudden deafness can be due to head trauma, vascular diseases, infections, or can appear without obvious cause or warning.Hearing: The ability or act of sensing and transducing ACOUSTIC STIMULATION to the CENTRAL NERVOUS SYSTEM. It is also called audition.Prostheses and Implants: Artificial substitutes for body parts, and materials inserted into tissue for functional, cosmetic, or therapeutic purposes. Prostheses can be functional, as in the case of artificial arms and legs, or cosmetic, as in the case of an artificial eye. Implants, all surgically inserted or grafted into the body, tend to be used therapeutically. IMPLANTS, EXPERIMENTAL is available for those used experimentally.Vascular Surgical Procedures: Operative procedures for the treatment of vascular disorders.Efferent Pathways: Nerve structures through which impulses are conducted from a nerve center toward a peripheral site. Such impulses are conducted via efferent neurons (NEURONS, EFFERENT), such as MOTOR NEURONS, autonomic neurons, and hypophyseal neurons.Patellar Ligament: A band of fibrous tissue that attaches the apex of the PATELLA to the lower part of the tubercle of the TIBIA. The ligament is actually the caudal continuation of the common tendon of the QUADRICEPS FEMORIS. The patella is embedded in that tendon. As such, the patellar ligament can be thought of as connecting the quadriceps femoris tendon to the tibia, and therefore it is sometimes called the patellar tendon.Facial Nerve: The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and SALIVARY GLANDS, and convey afferent information for TASTE from the anterior two-thirds of the TONGUE and for TOUCH from the EXTERNAL EAR.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.Freeze Fracturing: Preparation for electron microscopy of minute replicas of exposed surfaces of the cell which have been ruptured in the frozen state. The specimen is frozen, then cleaved under high vacuum at the same temperature. The exposed surface is shadowed with carbon and platinum and coated with carbon to obtain a carbon replica.Alveolar Process: The thickest and spongiest part of the maxilla and mandible hollowed out into deep cavities for the teeth.Emergency Treatment: First aid or other immediate intervention for accidents or medical conditions requiring immediate care and treatment before definitive medical and surgical management can be procured.Balloon Occlusion: Use of a balloon CATHETER to block the flow of blood through an artery or vein.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.Head: The upper part of the human body, or the front or upper part of the body of an animal, typically separated from the rest of the body by a neck, and containing the brain, mouth, and sense organs.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Allantois: An extra-embryonic membranous sac derived from the YOLK SAC of REPTILES; BIRDS; and MAMMALS. It lies between two other extra-embryonic membranes, the AMNION and the CHORION. The allantois serves to store urinary wastes and mediate exchange of gas and nutrients for the developing embryo.Intracranial Arteriovenous Malformations: Congenital vascular anomalies in the brain characterized by direct communication between an artery and a vein without passing through the CAPILLARIES. The locations and size of the shunts determine the symptoms including HEADACHES; SEIZURES; STROKE; INTRACRANIAL HEMORRHAGES; mass effect; and vascular steal effect.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Decompression, Surgical: A surgical operation for the relief of pressure in a body compartment or on a body part. (From Dorland, 28th ed)Decidua: The hormone-responsive glandular layer of ENDOMETRIUM that sloughs off at each menstrual flow (decidua menstrualis) or at the termination of pregnancy. During pregnancy, the thickest part of the decidua forms the maternal portion of the PLACENTA, thus named decidua placentalis. The thin portion of the decidua covering the rest of the embryo is the decidua capsularis.Placenta Diseases: Pathological processes or abnormal functions of the PLACENTA.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Angiography: Radiography of blood vessels after injection of a contrast medium.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Chorion: The outermost extra-embryonic membrane surrounding the developing embryo. In REPTILES and BIRDS, it adheres to the shell and allows exchange of gases between the egg and its environment. In MAMMALS, the chorion evolves into the fetal contribution of the PLACENTA.Labyrinth Supporting Cells: Cells forming a framework supporting the sensory AUDITORY HAIR CELLS in the organ of Corti. Lateral to the medial inner hair cells, there are inner pillar cells, outer pillar cells, Deiters cells, Hensens cells, Claudius cells, Boettchers cells, and others.Radiography, Interventional: Diagnostic and therapeutic procedures that are invasive or surgical in nature, and require the expertise of a specially trained radiologist. In general, they are more invasive than diagnostic imaging but less invasive than major surgery. They often involve catheterization, fluoroscopy, or computed tomography. Some examples include percutaneous transhepatic cholangiography, percutaneous transthoracic biopsy, balloon angioplasty, and arterial embolization.Neuroma, Acoustic: A benign SCHWANNOMA of the eighth cranial nerve (VESTIBULOCOCHLEAR NERVE), mostly arising from the vestibular branch (VESTIBULAR NERVE) during the fifth or sixth decade of life. Clinical manifestations include HEARING LOSS; HEADACHE; VERTIGO; TINNITUS; and FACIAL PAIN. Bilateral acoustic neuromas are associated with NEUROFIBROMATOSIS 2. (From Adams et al., Principles of Neurology, 6th ed, p673)Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Septal Occluder Device: A CATHETER-delivered implant used for closing abnormal holes in the cardiovascular system, especially HEART SEPTAL DEFECTS; or passageways intentionally made during cardiovascular surgical procedures.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Capillary Permeability: The property of blood capillary ENDOTHELIUM that allows for the selective exchange of substances between the blood and surrounding tissues and through membranous barriers such as the BLOOD-AIR BARRIER; BLOOD-AQUEOUS BARRIER; BLOOD-BRAIN BARRIER; BLOOD-NERVE BARRIER; BLOOD-RETINAL BARRIER; and BLOOD-TESTIS BARRIER. Small lipid-soluble molecules such as carbon dioxide and oxygen move freely by diffusion. Water and water-soluble molecules cannot pass through the endothelial walls and are dependent on microscopic pores. These pores show narrow areas (TIGHT JUNCTIONS) which may limit large molecule movement.Pleural Effusion: Presence of fluid in the pleural cavity resulting from excessive transudation or exudation from the pleural surfaces. It is a sign of disease and not a diagnosis in itself.Subarachnoid Hemorrhage: Bleeding into the intracranial or spinal SUBARACHNOID SPACE, most resulting from INTRACRANIAL ANEURYSM rupture. It can occur after traumatic injuries (SUBARACHNOID HEMORRHAGE, TRAUMATIC). Clinical features include HEADACHE; NAUSEA; VOMITING, nuchal rigidity, variable neurological deficits and reduced mental status.Cauda Equina: The lower part of the SPINAL CORD consisting of the lumbar, sacral, and coccygeal nerve roots.Fetal Development: Morphological and physiological development of FETUSES.Ischemia: A hypoperfusion of the BLOOD through an organ or tissue caused by a PATHOLOGIC CONSTRICTION or obstruction of its BLOOD VESSELS, or an absence of BLOOD CIRCULATION.Decerebrate State: A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. (From Adams et al., Principles of Neurology, 6th ed, p358)Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Endothelium: A layer of epithelium that lines the heart, blood vessels (ENDOTHELIUM, VASCULAR), lymph vessels (ENDOTHELIUM, LYMPHATIC), and the serous cavities of the body.Uterus: The hollow thick-walled muscular organ in the female PELVIS. It consists of the fundus (the body) which is the site of EMBRYO IMPLANTATION and FETAL DEVELOPMENT. Beyond the isthmus at the perineal end of fundus, is CERVIX UTERI (the neck) opening into VAGINA. Beyond the isthmi at the upper abdominal end of fundus, are the FALLOPIAN TUBES.Cerebral Ventricles: Four CSF-filled (see CEREBROSPINAL FLUID) cavities within the cerebral hemispheres (LATERAL VENTRICLES), in the midline (THIRD VENTRICLE) and within the PONS and MEDULLA OBLONGATA (FOURTH VENTRICLE).Surgical Procedures, Minimally Invasive: Procedures that avoid use of open, invasive surgery in favor of closed or local surgery. These generally involve use of laparoscopic devices and remote-control manipulation of instruments with indirect observation of the surgical field through an endoscope or similar device.Hearing Loss: A general term for the complete or partial loss of the ability to hear from one or both ears.Hearing Loss, Sensorineural: Hearing loss resulting from damage to the COCHLEA and the sensorineural elements which lie internally beyond the oval and round windows. These elements include the AUDITORY NERVE and its connections in the BRAINSTEM.Laminectomy: A surgical procedure that entails removing all (laminectomy) or part (laminotomy) of selected vertebral lamina to relieve pressure on the SPINAL CORD and/or SPINAL NERVE ROOTS. Vertebral lamina is the thin flattened posterior wall of vertebral arch that forms the vertebral foramen through which pass the spinal cord and nerve roots.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Spinal Nerve Roots: Paired bundles of NERVE FIBERS entering and leaving the SPINAL CORD at each segment. The dorsal and ventral nerve roots join to form the mixed segmental spinal nerves. The dorsal roots are generally afferent, formed by the central projections of the spinal (dorsal root) ganglia sensory cells, and the ventral roots are efferent, comprising the axons of spinal motor and PREGANGLIONIC AUTONOMIC FIBERS.Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.Dura Mater: The outermost of the three MENINGES, a fibrous membrane of connective tissue that covers the brain and the spinal cord.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Vascular Endothelial Growth Factor A: The original member of the family of endothelial cell growth factors referred to as VASCULAR ENDOTHELIAL GROWTH FACTORS. Vascular endothelial growth factor-A was originally isolated from tumor cells and referred to as "tumor angiogenesis factor" and "vascular permeability factor". Although expressed at high levels in certain tumor-derived cells it is produced by a wide variety of cell types. In addition to stimulating vascular growth and vascular permeability it may play a role in stimulating VASODILATION via NITRIC OXIDE-dependent pathways. Alternative splicing of the mRNA for vascular endothelial growth factor A results in several isoforms of the protein being produced.Surgical Procedures, Elective: Surgery which could be postponed or not done at all without danger to the patient. Elective surgery includes procedures to correct non-life-threatening medical problems as well as to alleviate conditions causing psychological stress or other potential risk to patients, e.g., cosmetic or contraceptive surgery.Laparoscopy: A procedure in which a laparoscope (LAPAROSCOPES) is inserted through a small incision near the navel to examine the abdominal and pelvic organs in the PERITONEAL CAVITY. If appropriate, biopsy or surgery can be performed during laparoscopy.Eye Movements: Voluntary or reflex-controlled movements of the eye.In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Fetal Death: Death of the developing young in utero. BIRTH of a dead FETUS is STILLBIRTH.Postural Balance: A POSTURE in which an ideal body mass distribution is achieved. Postural balance provides the body carriage stability and conditions for normal functions in stationary position or in movement, such as sitting, standing, or walking.Tendinopathy: Clinical syndrome describing overuse tendon injuries characterized by a combination of PAIN, diffuse or localized swelling, and impaired performance. Distinguishing tendinosis from tendinitis is clinically difficult and can be made only after histopathological examination.Organ Size: The measurement of an organ in volume, mass, or heaviness.Endothelial Cells: Highly specialized EPITHELIAL CELLS that line the HEART; BLOOD VESSELS; and lymph vessels, forming the ENDOTHELIUM. They are polygonal in shape and joined together by TIGHT JUNCTIONS. The tight junctions allow for variable permeability to specific macromolecules that are transported across the endothelial layer.Kidney Glomerulus: A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue.Intraoperative Care: Patient care procedures performed during the operation that are ancillary to the actual surgery. It includes monitoring, fluid therapy, medication, transfusion, anesthesia, radiography, and laboratory tests.Electrooculography: Recording of the average amplitude of the resting potential arising between the cornea and the retina in light and dark adaptation as the eyes turn a standard distance to the right and the left. The increase in potential with light adaptation is used to evaluate the condition of the retinal pigment epithelium.Reoperation: A repeat operation for the same condition in the same patient due to disease progression or recurrence, or as followup to failed previous surgery.Radiographic Image Enhancement: Improvement in the quality of an x-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed.Fetal Growth Retardation: The failure of a FETUS to attain its expected FETAL GROWTH at any GESTATIONAL AGE.Lymphatic System: A system of organs and tissues that process and transport immune cells and LYMPH.Embolization, Therapeutic: A method of hemostasis utilizing various agents such as Gelfoam, silastic, metal, glass, or plastic pellets, autologous clot, fat, and muscle as emboli. It has been used in the treatment of spinal cord and INTRACRANIAL ARTERIOVENOUS MALFORMATIONS, renal arteriovenous fistulas, gastrointestinal bleeding, epistaxis, hypersplenism, certain highly vascular tumors, traumatic rupture of blood vessels, and control of operative hemorrhage.Cerebral Arterial Diseases: Pathological conditions of intracranial ARTERIES supplying the CEREBRUM. These diseases often are due to abnormalities or pathological processes in the ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; and POSTERIOR CEREBRAL ARTERY.Reflex: An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.Mice, Inbred C57BLForelimb: A front limb of a quadruped. (The Random House College Dictionary, 1980)Embryonic and Fetal Development: Morphological and physiological development of EMBRYOS or FETUSES.Gestational Age: The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.Microscopy, Electron, Transmission: Electron microscopy in which the ELECTRONS or their reaction products that pass down through the specimen are imaged below the plane of the specimen.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.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Hair Cells, Auditory: Sensory cells in the organ of Corti, characterized by their apical stereocilia (hair-like projections). The inner and outer hair cells, as defined by their proximity to the core of spongy bone (the modiolus), change morphologically along the COCHLEA. Towards the cochlear apex, the length of hair cell bodies and their apical STEREOCILIA increase, allowing differential responses to various frequencies of sound.Radiographic Image Interpretation, Computer-Assisted: Computer systems or networks designed to provide radiographic interpretive information.Heart Function Tests: Examinations used to diagnose and treat heart conditions.Deafness: A general term for the complete loss of the ability to hear from both ears.Elasticity: Resistance and recovery from distortion of shape.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.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.Neck: The part of a human or animal body connecting the HEAD to the rest of the body.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Fluorescein-5-isothiocyanate: Fluorescent probe capable of being conjugated to tissue and proteins. It is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.Preoperative Care: Care given during the period prior to undergoing surgery when psychological and physical preparations are made according to the special needs of the individual patient. This period spans the time between admission to the hospital to the time the surgery begins. (From Dictionary of Health Services Management, 2d ed)Catheterization: Use or insertion of a tubular device into a duct, blood vessel, hollow organ, or body cavity for injecting or withdrawing fluids for diagnostic or therapeutic purposes. It differs from INTUBATION in that the tube here is used to restore or maintain patency in obstructions.Maternal-Fetal Exchange: Exchange of substances between the maternal blood and the fetal blood at the PLACENTA via PLACENTAL CIRCULATION. The placental barrier excludes microbial or viral transmission.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.PrimatesGene Targeting: The integration of exogenous DNA into the genome of an organism at sites where its expression can be suitably controlled. This integration occurs as a result of homologous recombination.Hepatectomy: Excision of all or part of the liver. (Dorland, 28th ed)Lumbar Vertebrae: VERTEBRAE in the region of the lower BACK below the THORACIC VERTEBRAE and above the SACRAL VERTEBRAE.