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Aquaeductus Vestibuli
At the posterior lateral wall of the temporal bone is the vestibular aqueduct, which extends to the posterior surface of the petrous portion of the temporal bone. The vestibular aqueduct parallels the petrous apex, in contrast to the cochlear aqueduct, which lies perpendicular to the petrous apex. It transmits a small vein, and contains a tubular prolongation of the membranous labyrinth, the ductus endolymphaticus, which ends in a cul-de-sac, the endolymphatic sac, between the layers of the dura mater within the cranial cavity. Pathology Enlargement of the vestibular aqueduct to greater than 2 mm is associated with enlarged vestibular aqueduct syndrome, a disease entity that is associated with one-sided hearing loss in children. The diagnosis can be made by high resolution CT or MRI, with comparison to the adjacent posterior semicircular canal. If the vestibular aqueduct is larger in size, and the clinical presentation is consistent, the diagnosis can be made. Treatmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Labyrinth (inner Ear)
The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule of the ear, vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the substance of the bone, and lined by periosteum. They contain a clear fluid, the perilymph, in which the membranous labyrinth is situated. A Bone fracture, fracture classification system in which temporal bone fractures detected by CT scan, computed tomography are delineated based on disruption of the otic capsule has been found to be predictive for complications of temporal bone trauma such as Facial nerve injuries, facial nerve injury, sensorineural deafness and cerebrospinal fluid otorrhea. On radiographic images, the otic capsule is the densest portion of the temporal bone. In otospongiosis, a leading cause of adult-onset hearing loss, the otic capsule is exclusively affected. This area normally undergoes no remodel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endolymphatic Sac
From the posterior wall of the saccule a canal, the endolymphatic duct, is given off; this duct is joined by the utriculosaccular duct, and then passes along the vestibular aqueduct and ends in a blind pouch, the endolymphatic sac, on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater. Studies suggest that the endolymphatic duct and endolymphatic sac perform both absorptive and secretory, as well as phagocytic and immunodefensive, functions. Fittingly, contrast agent uptake in the endolymphatic sac and duct in MRI is inversely correlated to endolymphatic hydrops Endolymphatic hydrops is a disorder of the inner ear. It consists of an excessive build-up of the endolymph fluid, which fills the hearing and balance structures of the inner ear. Endolymph fluid, which is partly regulated by the endolymph sac, ...,J. Gerb, E. Kierig, V. Kirsch, Sandra Becker‐Bense, Rainer Boegle, Thomas Brandt, Marianne Dieterich: ''Contras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cochlear Implants
A cochlear implant (CI) is a surgically implanted neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception. With the help of therapy, cochlear implants may allow for improved speech understanding in both quiet and noisy environments. A CI bypasses acoustic hearing by direct electrical stimulation of the auditory nerve. Through everyday listening and auditory training, cochlear implants allow both children and adults to learn to interpret those signals as speech and sound. The implant has two main components. The outside component is generally worn behind the ear, but could also be attached to clothing, for example, in young children. This component, the sound processor, contains microphones, electronics that include digital signal processor (DSP) chips, battery, and a coil that transmits a signal to the implant across the skin. The inside component, the actual implant, has a coil to receive signals, electronics, and an a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semicircular Canal
The semicircular canals are three semicircular interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the lateral, anterior and posterior semicircular canals. They are the part of the bony labyrinth, a periosteum-lined cavity on the petrous part of the temporal bone filled with perilymph. Each semicircular canal contains its respective semicircular duct, i.e. the lateral, anterior and posterior semicircular ducts, which provide the sensation of angular acceleration and are part of the membranous labyrinth—therefore filled with endolymph. Structure The semicircular canals are a component of the bony labyrinth that are at right angles from each other and contain their respective semicircular duct. At one end of each of the semicircular ducts is a dilated sac called a membranous ampulla, which is more than twice the diameter of the ducts. Each ampulla contains an ampullary crest, the crista ampullaris which consists of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computed Tomography
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists. CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated. Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, it can also be used to form images of non-living objects. The 1979 N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deafness
Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written with a lower case ''d''. It later came to be used in a cultural context to refer to those who primarily communicate with a deafness aid or through sign language regardless of hearing ability, often capitalized as ''Deaf'' and referred to as "big D Deaf" in speech and sign. The two definitions overlap but are not identical, as hearing loss includes cases that are not severe enough to impact spoken language comprehension, while cultural Deafness includes hearing people who use sign language, such as children of deaf adults. Medical context In a medical context, deafness is defined as a degree of hearing difficulties such that a person is unable to understand speech, even in the presence of amplification. In profound deafness, eve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enlarged Vestibular Aqueduct Syndrome
Large vestibular aqueduct is a structural deformity of the inner ear. Enlargement of this duct is one of the most common inner ear deformities and is commonly associated with hearing loss during childhood. The term was first discovered in 1791 by Mondini when he was completing a temporal bone dissection. It was then defined by Valvassori and Clemis as a vestibular aqueduct that is greater than or equal to 2.0 mm at the operculum and/or greater than or equal to 1.0 mm at the midpoint. Some use the term enlarged vestibular aqueduct syndrome, but this is felt by others to be erroneous as it is a clinical finding which can occur in several syndromes. Symptoms Although large vestibular aqueducts are a congenital disorder, congenital condition, hearing loss may not be present from birth. Age of diagnosis ranges from infancy to adulthood, and symptoms include fluctuating and sometimes progressive sensorineural hearing loss and Disequilibrium (medicine), disequilibrium. It is possible that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Cavity
The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull is also known as the cranium. The cranial cavity is formed by eight cranial bones known as the neurocranium that in humans includes the skull cap and forms the protective case around the brain. The remainder of the skull is the facial skeleton. The meninges are three protective membranes that surround the brain to minimize damage to the brain in the case of head trauma. Meningitis is the inflammation of meninges caused by bacterial or viral infections. Structure The capacity of an adult human cranial cavity is 1,200–1,700 cm3. The spaces between meninges and the brain are filled with a clear cerebrospinal fluid, increasing the protection of the brain. Facial bones of the skull are not included in the cranial cavity. There are only eight cranial bones: The occipital, sphenoid, frontal, ethmoid, two parietal, and two temporal bones are fused to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cul-de-sac
A dead end, also known as a ''cul-de-sac'' (; , ), a no-through road or a no-exit road, is a street with only one combined inlet and outlet. Dead ends are added to roads in urban planning designs to limit traffic in residential areas. Some dead ends prohibit all-through traffic, while others allow cyclists, pedestrians, or other non-automotive traffic to pass through connecting easements or paths. The latter case is an example of filtered permeability. The International Federation of Pedestrians proposed calling such streets "living end streets" and to provide signage at the entry of the streets that clearly indicates non-automotive permeability. This would retain the dead end's primary function as a non-through road, but establish complete pedestrian and bicycle network connectivity. "Dead end" is not the most commonly used expression in all English-speaking regions. Official terminology and traffic signs include many alternatives; some are only used regionally. In th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cochlea
The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (cochlea), modiolus. A core component of the cochlea is the organ of Corti, the sensory organ of hearing, which is distributed along the partition separating the fluid chambers in the coiled tapered tube of the cochlea. Etymology The name 'cochlea' is derived from the Latin word for ''snail shell'', which in turn is from the Greek language, Ancient Greek κοχλίας ''kokhlias'' ("snail, screw"), and from κόχλος ''kokhlos'' ("spiral shell") in reference to its coiled shape; the cochlea is coiled in mammals with the exception of monotremes. Structure The cochlea (: cochleae) is a spiraled, hollow, conical chamber of bone, in which waves propagate from the base (near the middle ear and the oval window) to the apex (the top or center of the spiral). The spiral canal of the cochlea is a section of the b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
