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Aquæductus Vestibuli
At the hinder part of the medial wall of the vestibule is the orifice of the vestibular aqueduct, which extends to the posterior surface of the petrous portion of the temporal bone. 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. Treatment is with mechanical hearing implants. There is an association with Pendred syndrome Pendred syndrome is a genetic diso ... [...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, 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 fracture classification system in which temporal bone fractures detected by 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 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 remodeling in adult life and is extremely dense. With otospongiosis, the ... [...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 minus the mandible is called the ''cranium''. The 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 called the facial skeleton. Meninges are protective membranes that surround the brain to minimize damage of the brain when there is 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 tog ... [...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 ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semicircular Canal
In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line of symmetry (reflection symmetry). In non-technical usage, the term "semicircle" is sometimes used to refer to a half-disk, which is a two-dimensional geometric shape that also includes the diameter segment from one end of the arc to the other as well as all the interior points. By Thales' theorem, any triangle inscribed in a semicircle with a vertex at each of the endpoints of the semicircle and the third vertex elsewhere on the semicircle is a right triangle, with a right angle at the third vertex. All lines intersecting the semicircle perpendicularly are concurrent at the center of the circle containing the given semicircle. Uses A semicircle can be used to construct the arithmetic and geometric means of two lengths using straight-e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from CT and 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, though "Open" MRI designs mostly relieve this. Additionally, implants and oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computed Tomography
A computed tomography scan (CT scan; formerly called computed axial tomography scan or 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 Nob ... [...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 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 difference such that a person is unable to understand speech, even in the presence of amplification. In profound deafness, even the highest intensity sound ... [...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 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. It is possible that a small portion of those with large vestibular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dura Mater
In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. The other two meningeal layers are the arachnoid mater and the pia mater. It envelops the arachnoid mater, which is responsible for keeping in the cerebrospinal fluid. It is derived primarily from the neural crest cell population, with postnatal contributions of the paraxial mesoderm. Structure The dura mater has several functions and layers. The dura mater is a membrane that envelops the arachnoid mater. It surrounds and supports the dural sinuses (also called dural venous sinuses, cerebral sinuses, or cranial sinuses) and carries blood from the brain toward the heart. Cranial dura mater has two layers called ''lamellae'', a superficial layer (also called the periosteal layer), which serves as the skull's inner periosteum, called the ... [...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. 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. The name cochlea derives . Structure The cochlea (plural is 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 bony labyrinth of the inner ear that is approximately 30 mm long and makes 2 turns about the modiolus. The cochlear structures include: * Three ''scalae'' or chambers: ** the vestibular duct or ''scala vestibuli'' (containing perilymph), which lies superior to the cochlear duct and abuts the oval window ** the ty ... [...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 In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. .... Studies suggest that the endolymphatic duct and endolymphatic sac perform both absorptive and secretory, as well as phagocytic and immunodefensive, functions.Wackym PA, Friberg U, Linthicum FH Jr, et al. Human endolymphatic sac: morphologic evidence of immunologic function. Ann Otol Rhinol Laryngol 1987;96:276–282 Neoplasms of the endolymphatic sac are very rare tumors. References E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cul-de-sac
A dead end, also known as a cul-de-sac (, from French for 'bag-bottom'), no through road or no exit road, is a street with only one inlet or outlet. The term "dead end" is understood in all varieties of English, but the official terminology and traffic signs include many different alternatives. Some of these are used only regionally. In the United States and other countries, ''cul-de-sac'' is often not an exact synonym for ''dead end'' and refers to dead ends with a circular end, allowing for easy turning at the end of the road. In Australia and Canada, they are usually referred to as a ''court'' when they have a bulbous end. Dead ends are added to road layouts in urban planning to limit through-traffic in residential areas. While some dead ends provide no possible passage except in and out of their road entry, others allow cyclists, pedestrians or other non-automotive traffic to pass through connecting easements or paths, an example of filtered permeability. The Internation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
