Stapes
Stapes Surgery
Stapes Mobilization
Otosclerosis
Ear Ossicles
Ossicular Prosthesis
Temporal Bone
Ear, Middle
Oval Window, Ear
Tympanic Membrane
Malleus
Tympanoplasty
Incus
Hearing Loss, Conductive
Ear Canal
Round Window, Ear
Perilymph
Fenestration, Labyrinth
Basilar Membrane
Bone Conduction
Stapedius
Acoustic Impedance Tests
A persistent pharyngohyostapedial artery: embryologic implications. (1/68)
A 3-year-old child was examined because of otorrhagia. CT scans showed an unusual vessel, confirmed by angiography, related to a persistent pharyngohyostapedial artery. This embryonic persistent artery associated with the normal internal carotid artery would explain the "duplication" aspect of the internal carotid artery. (+info)Comparing in vitro, in situ, and in vivo experimental data in a three-dimensional model of mammalian cochlear mechanics. (2/68)
Normal mammalian hearing is refined by amplification of the motion of the cochlear partition. This partition, comprising the organ of Corti sandwiched between the basilar and tectorial membranes, contains the outer hair cells that are thought to drive this amplification process. Force generation by outer hair cells has been studied extensively in vitro and in situ, but, to understand cochlear amplification fully, it is necessary to characterize the role played by each of the components of the cochlear partition in vivo. Observations of cochlear partition motion in vivo are severely restricted by its inaccessibility and sensitivity to surgical trauma, so, for the present study, a computer model has been used to simulate the operation of the cochlea under different experimental conditions. In this model, which uniquely retains much of the three-dimensional complexity of the real cochlea, the motions of the basilar and tectorial membranes are fundamentally different during in situ- and in vivo-like conditions. Furthermore, enhanced outer hair cell force generation in vitro leads paradoxically to a decrease in the gain of the cochlear amplifier during sound stimulation to the model in vivo. These results suggest that it is not possible to extrapolate directly from experimental observations made in vitro and in situ to the normal operation of the intact organ in vivo. (+info)Targeted mutagenesis of the POU-domain gene Brn4/Pou3f4 causes developmental defects in the inner ear. (3/68)
Targeted mutagenesis in mice demonstrates that the POU-domain gene Brn4/Pou3f4 plays a crucial role in the patterning of the mesenchymal compartment of the inner ear. Brn4 is expressed extensively throughout the condensing mesenchyme of the developing inner ear. Mutant animals displayed behavioral anomalies that resulted from functional deficits in both the auditory and vestibular systems, including vertical head bobbing, changes in gait, and hearing loss. Anatomical analyses of the temporal bone, which is derived in part from the otic mesenchyme, demonstrated several dysplastic features in the mutant animals, including enlargement of the internal auditory meatus. Many phenotypic features of the mutant animals resulted from the reduction or thinning of the bony compartment of the inner ear. Histological analyses demonstrated a hypoplasia of those regions of the cochlea derived from otic mesenchyme, including the spiral limbus, the scala tympani, and strial fibrocytes. Interestingly, we observed a reduction in the coiling of the cochlea, which suggests that Brn-4 plays a role in the epithelial-mesenchymal communication necessary for the cochlear anlage to develop correctly. Finally, the stapes demonstrated several malformations, including changes in the size and morphology of its footplate. Because the stapes anlage does not express the Brn4 gene, stapes malformations suggest that the Brn4 gene also plays a role in mesenchymal-mesenchymal signaling. On the basis of these data, we suggest that Brn-4 enhances the survival of mesodermal cells during the mesenchymal remodeling that forms the mature bony labyrinth and regulates inductive signaling mechanisms in the otic mesenchyme. (+info)Parathyroid hormone-parathyroid hormone-related peptide receptor expression and function in otosclerosis. (4/68)
The aim of this study was to investigate the possibility that an abnormality related to parathyroid hormone (PTH) action is involved in the increased bone turnover observed in otosclerosis. To do so, expression and function of the PTH-PTH-related peptide (PTHrP) receptor were studied in the involved tissue (stapes) and compared with that in control bone sample obtained from the external auditory canal (EAC) in the same patient in 10 cases of otosclerosis and in 1 case of osteogenesis imperfecta. PTH-PTHrP receptor expression was studied by RT-PCR of RNA prepared from cultured cells in three patients and RNA directly extracted from bone samples in four patients. PTH-PTHrP receptor function was assessed by measuring the stimulation of cAMP production by 0.8, 8, and 80 nM PTH in bone cell cultures in seven cases. Results showed that PTH-PTHrP receptor mRNA expression in the otosclerotic stapes was lower than that in EAC samples (P < 0.05), whereas it was higher in stapes than that in EAC in the case of osteogenesis imperfecta. cAMP production after PTH stimulation was lower in bone cells cultured from otosclerotic stapes compared with that in cells cultured from EAC (range of increase in stimulation: 0.8-4.5 and 1.5-7 in stapes and EAC bone cells, respectively, P < 0.05). In contrast, the stimulation of cAMP production by forskolin was not significantly different in otosclerotic stapes and EAC bone cells (range of increase in stimulation: 20.7-83.1 and 4.9-99.8 in stapes and EAC, respectively, P > 0.05). These results show a lower stimulation of cAMP production in response to PTH associated with a lower PTH-PTHrP receptor mRNA expression in pathological stapes from patients with otosclerosis compared with that in control EAC samples. This difference supports the hypothesis that an abnormal cellular response to PTH contributes to the abnormal bone turnover in otosclerosis. (+info)Congenital absence of the oval window: radiologic diagnosis and associated anomalies. (5/68)
BACKGROUND AND PURPOSE: In most children with conductive hearing loss, acquired otitis media and/or middle ear effusion are ultimately diagnosed. Congenital conductive hearing loss is a rare condition; absence of the oval window is an unusual pathogenesis for this type of hearing impairment and can be associated with an anomalous horizontal facial nerve canal. Our goal was to describe the imaging features of congenital absence of the oval window, to determine the frequency with which anomalous development of the horizontal facial nerve canal occurs, and to review the developmental error responsible for this malformation. METHODS: Nine temporal bones in seven patients (5 to 36 years old) were found to have an inadequately formed oval window on high-resolution CT scans; seven ears showed complete lack of oval window formation, and two showed partial absence of the oval window. Records were reviewed for clinical information, and images were examined for associated anomalies. RESULTS: Six of nine ears with abnormal oval window formation showed malposition of the horizontal facial nerve canal. In each of these, the canal was abnormally low, overlying the expected location of the oval window; three of the canals lacked a visible bony covering. Seven of the nine ears were found to have a dysplastic or absent stapes. CONCLUSION: Congenital absence of the oval window can be diagnosed on CT studies. In the present series, this anomaly was associated with a grossly aberrant horizontal facial nerve canal in six of nine involved ears. Familiarity with the developmental sequence of oval window formation fosters an understanding of these anomalies. Preoperative recognition is important clinically, as a low facial nerve will block surgical access to the oval window and its presence will alter patient management. (+info)No evidence of measles virus in stapes samples from patients with otosclerosis. (6/68)
Otosclerosis is a localized bone dystrophy of unknown etiology mainly involving the stapes. The hypothesis of a persistent infection by the measles virus was based on the inconstant detection of the virus by various methods, including reverse transcription-PCR (RT-PCR) of patients' stapes samples. The aim of this work was to investigate the presence of the measles virus in stapedial otosclerosis foci by different sensitive methods. Pathologic stapes samples were obtained from 35 patients suffering from otosclerosis. Measles virus detection was performed by (i) cocultures of Vero cells and primary cell cultures of bone samples (n = 7), (ii) immunofluorescence study of these cocultures (n = 3), and (iii) RT-PCR on RNA directly obtained from fresh frozen samples (n = 28) and on RNA extracted from the primary cell cultures (n = 2). Viral genomic regions coding for N (nucleoprotein) and M (matrix) proteins were separately amplified. PCR sensitivity was optimized on the measles virus Edmonston strain. Glyceraldehyde-3-phosphate dehydrogenase mRNA was used as a marker of total RNA recovery. PCR products were tested by Southern blot hybridization technique to improve sensitivity and specificity. PCRs amplifying the M and the N protein genes were able to detect the control measles virus RNA at titers as low as 0.1 and 0.01 50% tissue culture infective dose, respectively. With these highly sensitive methods, we could not evidence the presence of the measles virus in any of our bone samples or primary bone cell cultures. Our results do not confirm the hypothesis of persistent measles virus infection in otosclerosis. (+info)Development of wide-band middle ear transmission in the Mongolian gerbil. (7/68)
Stapes vibrations were measured in deeply anesthetized adult and neonatal (ages: 14 to 20 days) Mongolian gerbils. In adult gerbils, the velocity magnitude of stapes responses to tones was approximately constant over the entire frequency range of measurements, 1 to 40 kHz. Response phases referred to pressure near the tympanic membrane varied approximately linearly as a function of increasing stimulus frequency, with a slope corresponding to a group delay of 30 micros. In neonatal gerbils, the sensitivity of stapes responses to tones was lower than in adults, especially at mid-frequencies (e.g., by about 15 dB at 10-20 kHz in gerbils aged 14 days). The input impedance of the adult gerbil cochlea, calculated from stapes vibrations and published measurements of pressure in scala vestibuli near the oval window [E. Olson, J. Acoust. Soc. Am. 103, 3445-3463 (1998)], is principally dissipative at frequencies lower than 10 kHz. CONCLUSIONS: (a) middle-ear vibrations in adult gerbils do not limit the input to the cochlea up to at least 40 kHz, i.e., within 0.5 oct of the high-frequency cutoff of the behavioral audiogram; and (b) the results in both adult and neonatal gerbils are inconsistent with the hypothesis that mass reactance controls high-frequency ossicular vibrations and support the idea that the middle ear functions as a transmission line. (+info)Peripheral control of acoustic signals in the auditory system of echolocating bats. (8/68)
Many species of echolocating bats emit intense orientation sounds. If such intense sounds directly stimulated their ears, detection of faint echoes would be impaired. Therefore, possible mechanisms for the attenuation of self-stimulation were studied with Myotis lucifugus. The acoustic middle-ear-muscle reflex could perfectly and transiently regulate the amplitude of an incoming signal only at its beginning. However, its shortest latency in terms of electromyograms and of the attenuation of the cochlear microphonic was 3-4 and 4-8 msec, respectively, so that these muscles failed to attenuate orientation signals by the reflex. The muscles, however, received a message from the vocalization system when the bat vocalized, and contracted synchronously with vocalization. The duration of the contraction-relaxation was so short that the self-stimulation was attenuated, but the echoes were not. The tetanus-fusion frequency of tha stapedium muscle ranged between 260 and 320/sec. Unlike the efferent fibres in the lateral-line and vestibular systems, the olivo-cochlear bundle showed no sign of attenuation of self-stimulation. (+info)The stapes is the smallest bone in the human body, which is a part of the middle ear. It is also known as the "stirrup" because of its U-shaped structure. The stapes connects the inner ear to the middle ear, transmitting sound vibrations from the ear drum to the inner ear. More specifically, it is the third bone in the series of three bones (the ossicles) that conduct sound waves from the air to the fluid-filled inner ear.
Stapes surgery, also known as stapedectomy or stapedotomy, is a surgical procedure performed to correct hearing loss caused by otosclerosis. Otosclerosis is a condition in which the stapes bone in the middle ear becomes fixed and unable to vibrate properly, leading to conductive hearing loss.
During stapes surgery, the surgeon makes an incision behind the ear and creates a small opening in the eardrum. The fixed stapes bone is then removed or modified, and a prosthetic device is inserted in its place to allow sound vibrations to be transmitted to the inner ear. In some cases, a piece of tissue or artificial material may be used to fill the space left by the removed bone.
Stapedectomy involves complete removal of the stapes bone, while stapedotomy involves making a small hole in the stapes bone and inserting a prosthetic device through it. Both procedures are typically performed on an outpatient basis and have a high success rate in restoring hearing. However, as with any surgical procedure, there are risks involved, including infection, permanent hearing loss, and balance problems.
Stapes mobilization is a medical procedure that involves the partial or complete movement of the stapes bone in the middle ear. The stapes bone, also known as the stirrup, is one of the three smallest bones in the human body and plays a crucial role in hearing by transmitting sound vibrations from the inner ear to the cochlea.
Stapes mobilization is typically performed during surgery to treat conductive hearing loss caused by conditions such as otosclerosis, a hereditary disorder that causes abnormal bone growth in the middle ear. During the procedure, the surgeon creates an incision in the ear canal and removes a portion of the stapes bone or its surrounding tissue to allow for increased vibration and improved sound transmission.
The goal of stapes mobilization is to improve hearing by restoring normal function to the middle ear. However, like any surgical procedure, it carries risks such as infection, dizziness, and further hearing loss. Therefore, it is typically reserved for cases where other treatments have been unsuccessful or are not appropriate.
Otosclerosis is a medical condition that affects the bones in the middle ear. It is characterized by the abnormal growth and hardening (sclerosis) of the otosclerotic bone near the stapes footplate, one of the tiny bones in the middle ear (ossicles). This abnormal bone growth can cause stiffness or fixation of the stapes bone, preventing it from vibrating properly and leading to conductive hearing loss. In some cases, otosclerosis may also result in sensorineural hearing loss due to involvement of the inner ear structures. The exact cause of otosclerosis is not fully understood, but it is believed to have a genetic component and can sometimes be associated with pregnancy. Treatment options for otosclerosis include hearing aids or surgical procedures like stapedectomy or stapedotomy to bypass or remove the affected bone and improve hearing.
The ear ossicles are the three smallest bones in the human body, which are located in the middle ear. They play a crucial role in the process of hearing by transmitting and amplifying sound vibrations from the eardrum to the inner ear. The three ear ossicles are:
1. Malleus (hammer): The largest of the three bones, it is shaped like a hammer and connects to the eardrum.
2. Incus (anvil): The middle-sized bone, it looks like an anvil and connects the malleus to the stapes.
3. Stapes (stirrup): The smallest and lightest bone in the human body, it resembles a stirrup and transmits vibrations from the incus to the inner ear.
Together, these tiny bones work to efficiently transfer sound waves from the air to the fluid-filled cochlea of the inner ear, enabling us to hear.
An ossicular prosthesis is a medical device used to replace one or more of the small bones (ossicles) in the middle ear that are involved in hearing. These bones, known as the malleus, incus, and stapes, form a chain responsible for transmitting sound vibrations from the eardrum to the inner ear.
An ossicular prosthesis is typically made of biocompatible materials such as ceramic, plastic, or metal. The prosthesis is designed to bypass damaged or missing ossicles and reestablish the connection between the eardrum and the inner ear, thereby improving hearing function. Ossicular prostheses are often used in surgeries aimed at reconstructing the middle ear, such as tympanoplasty or stapedectomy, to treat various types of conductive hearing loss.
The temporal bone is a paired bone that is located on each side of the skull, forming part of the lateral and inferior walls of the cranial cavity. It is one of the most complex bones in the human body and has several important structures associated with it. The main functions of the temporal bone include protecting the middle and inner ear, providing attachment for various muscles of the head and neck, and forming part of the base of the skull.
The temporal bone is divided into several parts, including the squamous part, the petrous part, the tympanic part, and the styloid process. The squamous part forms the lateral portion of the temporal bone and articulates with the parietal bone. The petrous part is the most medial and superior portion of the temporal bone and contains the inner ear and the semicircular canals. The tympanic part forms the lower and anterior portions of the temporal bone and includes the external auditory meatus or ear canal. The styloid process is a long, slender projection that extends downward from the inferior aspect of the temporal bone and serves as an attachment site for various muscles and ligaments.
The temporal bone plays a crucial role in hearing and balance, as it contains the structures of the middle and inner ear, including the oval window, round window, cochlea, vestibule, and semicircular canals. The stapes bone, one of the three bones in the middle ear, is entirely encased within the petrous portion of the temporal bone. Additionally, the temporal bone contains important structures for facial expression and sensation, including the facial nerve, which exits the skull through the stylomastoid foramen, a small opening in the temporal bone.
The middle ear is the middle of the three parts of the ear, located between the outer ear and inner ear. It contains three small bones called ossicles (the malleus, incus, and stapes) that transmit and amplify sound vibrations from the eardrum to the inner ear. The middle ear also contains the Eustachian tube, which helps regulate air pressure in the middle ear and protects against infection by allowing fluid to drain from the middle ear into the back of the throat.
The oval window ( fenestra vestibuli ) is a small opening in the inner ear, specifically in the bony labyrinth of the temporal bone. It connects the middle ear to the vestibular system of the inner ear, more precisely to the vestibule. The oval window is covered by the base of the stapes, one of the three smallest bones in the human body, also known as the stirrup. This arrangement allows for the transmission of vibratory energy from the tympanic membrane (eardrum) to the inner ear, which is essential for hearing.
The tympanic membrane, also known as the eardrum, is a thin, cone-shaped membrane that separates the external auditory canal from the middle ear. It serves to transmit sound vibrations from the air to the inner ear, where they are converted into electrical signals that can be interpreted by the brain as sound. The tympanic membrane is composed of three layers: an outer layer of skin, a middle layer of connective tissue, and an inner layer of mucous membrane. It is held in place by several small bones and muscles and is highly sensitive to changes in pressure.
The Malleus is one of the three smallest bones in the human body, also known as the hammer. It's part of the ossicles in the middle ear, which are responsible for transmitting sound waves from the air to the fluid-filled inner ear. The malleus connects to the eardrum and its base articulates with the incus (anvil), the second of the three ossicles. Together, these bones help amplify and transfer sound vibrations to the inner ear, where they are converted into electrical signals that can be interpreted by the brain as sound.
Tympanoplasty is a surgical procedure performed to reconstruct or repair the tympanic membrane (eardrum) and/or the small bones of the middle ear (ossicles). The primary goal of this surgery is to restore hearing, but it can also help manage chronic middle ear infections, traumatic eardrum perforations, or cholesteatoma (a skin growth in the middle ear).
During the procedure, a surgeon may use various techniques such as grafting tissue from another part of the body to rebuild the eardrum or using prosthetic materials to reconstruct the ossicles. The choice of technique depends on the extent and location of the damage. Tympanoplasty is typically an outpatient procedure, meaning patients can return home on the same day of the surgery.
The incus, also known as the anvil, is one of the three smallest bones in the middle ear, located in the ossicular chain. It articulates with the malleus (hammer) and stapes (stirrup). The incus helps transmit and amplify sound vibrations from the eardrum to the inner ear.
Conductive hearing loss is a type of hearing loss that occurs when there is a problem with the outer or middle ear. Sound waves are not able to transmit efficiently through the ear canal to the eardrum and the small bones in the middle ear, resulting in a reduction of sound that reaches the inner ear. Causes of conductive hearing loss may include earwax buildup, fluid in the middle ear, a middle ear infection, a hole in the eardrum, or problems with the tiny bones in the middle ear. This type of hearing loss can often be treated through medical intervention or surgery.
The ear canal, also known as the external auditory canal, is the tubular passage that extends from the outer ear (pinna) to the eardrum (tympanic membrane). It is lined with skin and tiny hairs, and is responsible for conducting sound waves from the outside environment to the middle and inner ear. The ear canal is typically about 2.5 cm long in adults and has a self-cleaning mechanism that helps to keep it free of debris and wax.
The round window ( membrana tympani rotunda) is a small, thin membrane-covered opening located in the inner ear between the middle ear and the cochlea. It serves as one of the two openings that lead into the cochlea, with the other being the oval window.
The round window's primary function is to help regulate and dampen the pressure changes within the cochlea that occur when sound waves reach the inner ear. This is accomplished through the movement of the fluid-filled spaces inside the cochlea (the scala vestibuli and scala tympani) caused by vibrations from the stapes bone, which connects to the oval window.
As the stapes bone moves in response to sound waves, it causes a corresponding motion in the perilymph fluid within the cochlea. This movement then creates pressure changes at the round window, causing it to bulge outward or move inward. The flexibility of the round window allows it to absorb and dissipate these pressure changes, which helps protect the delicate structures inside the inner ear from damage due to excessive pressure buildup.
It is important to note that any damage or dysfunction in the round window can negatively impact hearing ability and cause various hearing disorders.
Perilymph is a type of fluid found in the inner ear, more specifically within the bony labyrinth of the inner ear. It fills the space between the membranous labyrinth and the bony labyrinth in the cochlea and vestibular system. Perilymph is similar in composition to cerebrospinal fluid (CSF) and contains sodium, chloride, and protein ions. Its main function is to protect the inner ear from damage, maintain hydrostatic pressure, and facilitate the transmission of sound waves to the hair cells in the cochlea for hearing.
Ossicular replacement is a surgical procedure in which the damaged or diseased ossicles (the three smallest bones in the middle ear, namely the malleus, incus, and stapes) are replaced with artificial prostheses. This procedure is often performed to correct hearing loss caused by various conditions such as chronic otitis media, cholesteatoma, or ossicular chain discontinuity.
The artificial prostheses used in ossicular replacement can be made of various materials, including ceramic, plastic, or metal. The choice of material depends on several factors, including the patient's individual needs and preferences, the size and shape of the remaining ossicles, and the surgeon's experience and preference.
The goal of ossicular replacement is to improve hearing by restoring the normal function of the ossicular chain, which is responsible for transmitting sound vibrations from the eardrum to the inner ear. By replacing the damaged or missing ossicles with artificial prostheses, the surgeon can help to restore the patient's ability to hear and communicate effectively.
'Fenestration, Labyrinth' is not a medical term that refers to a specific condition or diagnosis. However, I can provide you with some information about the individual terms:
1. Fenestration: In anatomy and physiology, fenestration refers to the presence of small windows or openings in a structure, usually in a blood vessel wall or within the inner ear. These openings allow for the passage of fluids, gases, or sound waves.
2. Labyrinth: The labyrinth is an anatomical term that describes a complex network of interconnected channels and cavities found primarily in two locations: the inner ear and certain structures within the brain.
In the inner ear, the bony labyrinth consists of three main parts: the vestibule, semicircular canals, and cochlea. These structures contain fluid-filled ducts and sacs that help maintain balance and transmit sound to the brain. The membranous labyrinth is a network of tubes and sacs within the bony labyrinth, containing endolymph fluid.
In summary, 'Fenestration, Labyrinth' may refer to the presence of fenestrations or openings in the structures of the labyrinth found in the inner ear. However, it is not a widely used medical term and does not have a specific definition within the field of medicine.
The basilar membrane is a key structure within the inner ear that plays a crucial role in hearing. It is a narrow, flexible strip of tissue located inside the cochlea, which is the spiral-shaped organ responsible for converting sound waves into neural signals that can be interpreted by the brain.
The basilar membrane runs along the length of the cochlea's duct and is attached to the rigid bony structures at both ends. It varies in width and stiffness along its length, with the widest and most flexible portion located near the entrance of the cochlea and the narrowest and stiffest portion located near the apex.
When sound waves enter the inner ear, they cause vibrations in the fluid-filled cochlear duct. These vibrations are transmitted to the basilar membrane, causing it to flex up and down. The specific pattern of flexion along the length of the basilar membrane depends on the frequency of the sound wave. Higher frequency sounds cause maximum flexion near the base of the cochlea, while lower frequency sounds cause maximum flexion near the apex.
As the basilar membrane flexes, it causes the attached hair cells to bend. This bending stimulates the hair cells to release neurotransmitters, which then activate the auditory nerve fibers. The pattern of neural activity in the auditory nerve encodes the frequency and amplitude of the sound wave, allowing the brain to interpret the sound.
Overall, the basilar membrane is a critical component of the hearing process, enabling us to detect and discriminate different sounds based on their frequency and amplitude.
Ankylosis is a medical term that refers to the abnormal joining or fusion of bones, typically in a joint. This can occur as a result of various conditions such as injury, infection, or inflammatory diseases like rheumatoid arthritis. The fusion of bones can restrict movement and cause stiffness in the affected joint. In some cases, ankylosis can lead to deformity and disability if not treated promptly and effectively.
There are different types of ankylosis depending on the location and extent of bone fusion. For instance, when it affects the spine, it is called "ankylosing spondylitis," which is a chronic inflammatory disease that can cause stiffness and pain in the joints between the vertebrae.
Treatment for ankylosis depends on the underlying cause and severity of the condition. In some cases, physical therapy or surgery may be necessary to restore mobility and function to the affected joint.
Bone conduction is a type of hearing mechanism that involves the transmission of sound vibrations directly to the inner ear through the bones of the skull, bypassing the outer and middle ears. This occurs when sound waves cause the bones in the skull to vibrate, stimulating the cochlea (the spiral cavity of the inner ear) and its hair cells, which convert the mechanical energy of the vibrations into electrical signals that are sent to the brain and interpreted as sound.
Bone conduction is a natural part of the hearing process in humans, but it can also be used artificially through the use of bone-conduction devices, such as hearing aids or headphones, which transmit sound vibrations directly to the skull. This type of transmission can provide improved hearing for individuals with conductive hearing loss, mixed hearing loss, or single-sided deafness, as it bypasses damaged or obstructed outer and middle ears.
The stapedius is a small muscle in the middle ear. It is the smallest striated muscle in the human body, with a mass of about 0.6 mg. The stapedius muscle arises from a pyramidal eminence on the posterior wall of the tympanic cavity and inserts into the neck of the stapes (one of the three ossicles in the middle ear).
The main function of the stapedius muscle is to protect the inner ear from loud sounds. When contracted, it pulls the stapes away from the oval window, reducing its mobility and thus decreasing the transmission of sound vibrations to the inner ear. This reflex action, known as the stapedial reflex or acoustic reflex, helps to prevent damage to the inner ear from excessive noise levels.
The afferent limb of the stapedial reflex is carried by the vestibular branch of the vestibulocochlear nerve (cranial nerve VIII), while the efferent limb is mediated by the facial nerve (cranial nerve VII). The reflex can be elicited by loud sounds, vocalizations, or even mental arithmetic tasks.
Acoustic impedance tests are diagnostic procedures used to measure the impedance or resistance of various parts of the ear to sound waves. These tests are often used to assess hearing function and diagnose any issues related to the middle ear, such as fluid buildup or problems with the eardrum.
The most common type of acoustic impedance test is tympanometry, which measures the mobility of the eardrum and the middle ear system by creating variations in air pressure within the ear canal. During this test, a small probe is inserted into the ear canal, and sound waves are generated while the pressure is varied. The resulting measurements provide information about the condition of the middle ear and can help identify any issues that may be affecting hearing.
Another type of acoustic impedance test is acoustic reflex testing, which measures the body's natural response to loud sounds. This involves measuring the contraction of the stapedius muscle in the middle ear, which occurs in response to loud noises. By measuring the strength and timing of this reflex, audiologists can gain additional insights into the functioning of the middle ear and identify any abnormalities that may be present.
Overall, acoustic impedance tests are important tools for diagnosing hearing problems and identifying any underlying issues in the middle ear. They are often used in conjunction with other hearing tests to provide a comprehensive assessment of an individual's hearing function.
A hearing test is a procedure used to evaluate a person's ability to hear different sounds, pitches, or frequencies. It is performed by a hearing healthcare professional in a sound-treated booth or room with calibrated audiometers. The test measures a person's hearing sensitivity at different frequencies and determines the quietest sounds they can hear, known as their hearing thresholds.
There are several types of hearing tests, including:
1. Pure Tone Audiometry (PTA): This is the most common type of hearing test, where the person is presented with pure tones at different frequencies and volumes through headphones or ear inserts. The person indicates when they hear the sound by pressing a button or raising their hand.
2. Speech Audiometry: This test measures a person's ability to understand speech at different volume levels. The person is asked to repeat words presented to them in quiet and in background noise.
3. Tympanometry: This test measures the function of the middle ear by creating variations in air pressure in the ear canal. It can help identify issues such as fluid buildup or a perforated eardrum.
4. Acoustic Reflex Testing: This test measures the body's natural response to loud sounds and can help identify the location of damage in the hearing system.
5. Otoacoustic Emissions (OAEs): This test measures the sound that is produced by the inner ear when it is stimulated by a sound. It can help identify cochlear damage or abnormalities.
Hearing tests are important for diagnosing and monitoring hearing loss, as well as identifying any underlying medical conditions that may be causing the hearing problems.
Synostosis is a medical term that refers to the abnormal or physiological fusion of adjacent bones. It's derived from two Greek words, "syn" meaning together and "osteon" meaning bone. In a normal physiological process, synostosis occurs during growth and development, where the growth of certain bones is stopped by the fusion of neighboring bones at specific sites known as sutures or fontanelles.
However, abnormal synostosis can occur due to various reasons such as injuries, infections, or genetic conditions. This can lead to restricted movement and growth disturbances in the affected area. Common examples include craniosynostosis, where the skull bones fuse prematurely, and syndactyly, where fingers or toes are fused together. Treatment for abnormal synostosis may involve surgery to correct the fusion and prevent further complications.