Otosclerosis is a congenital or spontaneous-onset disease characterized by abnormal bone remodeling in the inner ear. Often this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of conductive hearing loss. Clinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss. Otosclerosis is more likely in young age groups, and females. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.
Clinical relevance
Stapes
Stapes | Clinical relevance
Two common treatments are stapedectomy and stapedotomy Depending upon the severity and nature of the conductive loss, this type of hearing impairment can often be treated with surgical intervention or pharmaceuticals to partially or, in some cases, fully restore hearing acuity to within normal range. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole. Yes, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.
what are the 3 smallest bones in the human body
user
Strapes is one of them
assistant
what is the size of this above bone?
user
Roughly 3 x 2.5mm
assistant
which part of the body is this located?
user
Middle ear of humans
assistant
besides the human, is this bony structure present in other living species in the animal kingdom?
user
It is one of three ossicles in mammals, in non-mammalian four-legged animals its homologous form is called the columella
assistant
what are the functions this bony structure serves?
user
It transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear.
assistant
are there any variations of this bony structure?
user
It appears to be relatively constant in size in different ethnic groups
assistant
can this bony structure get affected or impaired?
user
Yes, its impairment causes conductive hearing loss
assistant
is there any remedy to solve this?
user
Otosclerosis is a congenital or spontaneous-onset disease characterized by abnormal bone remodeling in the inner ear. Often this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of conductive hearing loss. Clinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss. Otosclerosis is more likely in young age groups, and females. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.
Stapes | Clinical relevance
Occasionally the joints between the ossicles become rigid. One condition, otosclerosis, results in the fusing of the stapes to the oval window. This reduces hearing and may be treated surgically.
Ossicles | Clinical relevance
Surgery may be complicated by a persistent stapedial artery, fibrosis-related damage to the base of the bone, or obliterative otosclerosis, resulting in obliteration of the base.
Stapes | Clinical relevance
If the mobility of the stapes is reduced due to otosclerosis, then stapedius muscle contraction does not significantly decrease the admittance. When acoustic reflex testing is conducted, the acoustic reflex thresholds (ART) cannot be determined when attempting to measure on the affected side. Also, a conductive pathology will attenuate the test stimuli, resulting in either elevated reflex thresholds or absent reflexes when the stimulus is presented in the affected ear and measured in the other ear.
Otosclerosis | Audiometry
A stapedectomy is a surgical procedure of the middle ear performed in order to improve hearing. If the stapes footplate is fixed in position, rather than being normally mobile, then a conductive hearing loss results. There are two major causes of stapes fixation. The first is a disease process of abnormal mineralization of the temporal bone called otosclerosis. The second is a congenital malformation of the stapes. In both of these situations, it is possible to improve hearing by removing the stapes bone and replacing it with a micro prosthesis - a stapedectomy, or creating a small hole in the fixed stapes footplate and inserting a tiny, piston-like prosthesis - a stapedotomy.
Stapedectomy | Introduction
There are various methods to treat otosclerosis. However the method of choice is a procedure known as stapedectomy. Early attempts at hearing restoration via the simple freeing of the stapes from its sclerotic attachments to the oval window were met with temporary improvement in hearing, but the conductive hearing loss would almost always recur. A stapedectomy consists of removing a portion of the sclerotic stapes footplate and replacing it with an implant that is secured to the incus. This procedure restores continuity of ossicular movement and allows transmission of sound waves from the eardrum to the inner ear. A modern variant of this surgery called a stapedotomy, is performed by drilling a small hole in the stapes footplate with a micro-drill or a laser, and the insertion of a piston-like prothesis.
Otosclerosis | Surgery
The results of this surgery are generally most reliable in patients whose stapes has lost mobility because of otosclerosis. Nine out of ten patients who undergo the procedure will come out with significantly improved hearing while less than 1% will experience worsened hearing acuity or deafness. Successful surgery usually provides an increase in hearing acuity of about 20 dB. That is as much difference as having your hands over both ears, or not. However, most of the published results of success fall within the speech frequency of 500 Hz, 1000 Hz and 2000 Hz; poorer results are typically obtained in the high frequencies, but these are normally less hampered by otosclerosis in the first place.
Stapedectomy | Introduction
CHL in otosclerosis is caused by two main sites of involvement of the sclerotic (or scar-like) lesions. The best understood mechanism is fixation of the stapes footplate to the oval window of the cochlea. This greatly impairs movement of the stapes and therefore transmission of sound into the inner ear ("ossicular coupling"). Additionally the cochlea's round window can also become sclerotic, and in a similar way impair movement of sound pressure waves through the inner ear ("acoustic coupling"). Conductive hearing loss is usually concomitant with impingement of abnormal bone on the stapes footplate. This involvement of the oval window forms the basis of the name fenestral otosclerosis.
Otosclerosis | Pathophysiology
Fixation of the stapes within the oval window causes a conductive hearing loss. In pure-tone audiometry, this manifests as air-bone gaps on the audiogram (i.e. a difference of more than 10 dB between the air-conduction and bone-conduction thresholds at a given test frequency). However, medial fixation of the ossicular chain impairs both the inertial and osseotympanic modes of bone conduction, increasing the bone-conduction thresholds between 500 Hz and 4 kHz, and reducing the size of air-bone gaps. As 2 kHz is the resonant frequency of the ossicular chain, the largest increase in bone-conduction threshold (around 15 dB) occurs at this frequency – the resultant notch is called "Carhart's notch" and is a useful clinical marker for medial ossicular-chain fixation.
Otosclerosis | Audiometry
The stapes bone transmits movement to the oval window. As the stapes footplate moves into the oval window, the round window membrane moves out, and this allows movement of the fluid within the cochlea, leading to movement of the cochlear inner hair cells and thus hearing. If the round window were to be absent or rigidly fixed (as can happen in some congenital abnormalities), the stapes footplate would be pushing incompressible fluid against the unyielding walls of the cochlea. It would therefore not move to any useful degree leading to a hearing loss of about 60dB. This is, unsurprisingly, the same as for conditions where the stapes itself is fixed, such as otosclerosis.
Round window | Function
Complications of stapedectomy: When a stapedectomy is done in a middle ear with a congenitally fixed footplate, the results may be excellent but the risk of hearing damage is greater than when the stapes bone is removed and replaced (for otosclerosis). This is primarily due to the risk of additional anomalies being present in the congenitally abnormal ear. If high pressure within the fluid compartment that lies just below the stapes footplate exists, then a perilymphatic gusher may occur when the stapes is removed. Even without immediate complications during surgery, there is always concern of a perilymph fistula forming postoperatively.
Stapedectomy | Complications
The ossicles are suspended in the head and loosely coupled to the skull. When the head moves, the ossicles move out of phase with the head, but still follow the same cyclic motion. This causes the stapes to move in and out of the oval window. When vibrations come from the mastoid, inertial bone-conduction is greatest below 800 Hz. Putting the bone vibrator on the forehead instead of the mastoid does not significantly create this affect.
Bone conduction auditory brainstem response | Inertial bone-conduction
The morphology of the stapes suggests that the animal was capable of hearing high-frequency sound. "B. woodi" does not possess lateral line sulci or an ossified branchial system. The principal method of respiration was probably buccal (gulping air through mouth) rather than costal (expanding chest volume to take in air), indicated by the small straight ribs.
Balanerpeton | Introduction
The stapes appears to be relatively constant in size in different ethnic groups. In 0.01-0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all. Rarely, the stapes may be completely absent.
Stapes | Variation
A modified stapes operation, called a stapedotomy, is thought by many otologic surgeons to be safer and reduce the chances of postoperative complications. In stapedotomy, instead of removing the whole stapes footplate, a tiny hole is made in the footplate - either with a microdrill or with a laser, and a prosthesis is placed to touch this area, oval window. This procedure can be further improved by the use of a tissue graft seal of the fenestra, which is now common practice. Laser stapedotomy is a well-established surgical technique for treating conductive hearing loss due to otosclerosis. The procedure creates a tiny opening in the stapes (the smallest bone in the human body) in which to secure a prosthetic.
Stapedectomy | Stapedotomy
The configuration of the stapes is intermediate between non-amniote tetrapods and amniotes. On the one hand, its connection to the otic notch is unusual, since true reptiles and other amniotes have lost an otic notch, forcing the tympanum and stapes to shift downwards towards the quadrate bone of the jaw joint. On the other hand, the thin, sensitive structure of "Seymouria"'s stapes is a specialization over most non-amniote tetrapods, which have a thick stapes useless for hearing yet useful for reinforcing the skull. The inner ear of "Seymouria baylorensis" retains a cochlear recess located behind (rather than below) the vestibule, and its anterior semicircular canal was likely encompassed by a cartilaginous (rather than bony) supraoccipital.
Seymouria | Skull
The annular stapedial ligament (also called the stapediovestibular joint) is a ring of fibrous soft tissue that connects the base of the stapes to the oval window of the inner ear. Calcification and hardening of the annular ligament of the stapes (Otosclerosis) is a common cause of adult deafness.
Annular ligament of stapes | Introduction
Air vibrations could not set up pulsations through the skull as in a proper auditory organ. The spiracle was retained as the otic notch, eventually closed in by the tympanum, a thin, tight membrane. The hyomandibula of fish migrated upwards from its jaw supporting position, and was reduced in size to form the stapes. Situated between the tympanum and braincase in an air-filled cavity, the stapes was now capable of transmitting vibrations from the exterior of the head to the interior. Thus the stapes became an important element in an impedance matching system, coupling airborne sound waves to the receptor system of the inner ear.
Tetrapod | Hearing
The stapes or stirrup is a bone in the middle ear of humans and other mammals which is involved in the conduction of sound vibrations to the inner ear. This stirrup-shaped bone is connected to the oval window by its annular ligament, which allows the footplate to transmit sound energy through the oval window into the inner ear. The stapes is the smallest and lightest bone in the human body, and is so-called because of its resemblance to a stirrup ().
Stapes | Introduction
The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. The stapes is described as having a base, resting on the oval window, as well as a head that articulates with the incus. These are connected by anterior and posterior limbs (). The stapes articulates with the incus through the incudostapedial joint. The stapes is the smallest bone in the human body, and measures roughly 3 x 2.5mm, greater along the head-base span.
Stapes | Structure
Situated between the incus and the inner ear, the stapes transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear. The stapes is also stabilized by the stapedius muscle, which is innervated by the facial nerve.
Stapes | Function
For example, the lower branch of the squamosal bone is shortened to offset the tall dorsal process of quadratojugal which connects to it. On the other hand, the rear branch jugal bone lengthens to fill some of the space left by the shortening of the anterior process of the quadratojugal. In archosauriforms, the jugal even re-encloses the lower temporal fenestra. The stapes are long, thin, and solid, without a perforating hole (stapedial foramen) present in the more robust stapes of other reptiles.
Archosauromorpha | Skull
Scar tissue after ear infections may also make the eardrum dysfunction as well as when it is retracted and adherent to the medial part of the middle ear. Dysfunction of the three small bones of the middle ear – malleus, incus, and stapes – may cause conductive hearing loss. The mobility of the ossicles may be impaired for different reasons including a boney disorder of the ossicles called otosclerosis and disruption of the ossicular chain due to trauma, infection or ankylosis may also cause hearing loss.
Diagnosis of hearing loss | Type
The stapes is one of three ossicles in mammals. In non-mammalian four-legged animals, the bone homologous to the stapes is usually called the columella; however, in reptiles, either term may be used. In fish, the homologous bone is called the "hyomandibular", and is part of the gill arch supporting either the spiracle or the jaw, depending on the species. The equivalent term in amphibians is the "".
Stapes | Animals
The stapes develops from the second pharyngeal arch during the sixth to eighth week of embryological life. The central cavity of the stapes, the obturator foramen, is due to the presence embryologically of the stapedial artery, which usually regresses in humans during normal development.
Stapes | Development
This system had evolved independently within several different amphibian lineages. The impedance matching ear had to meet certain conditions to work. The stapes had to be perpendicular to the tympanum, small and light enough to reduce its inertia, and suspended in an air-filled cavity. In modern species that are sensitive to over 1 kHz frequencies, the footplate of the stapes is 1/20th the area of the tympanum. However, in early amphibians the stapes was too large, making the footplate area oversized, preventing the hearing of high frequencies. So it appears they could only hear high intensity, low frequency sounds—and the stapes more probably just supported the brain case against the cheek.
Tetrapod | Hearing
Paralysis of the stapedius allows wider oscillation of the stapes, resulting in heightened reaction of the auditory ossicles to sound vibration. This condition, known as hyperacusis, causes normal sounds to be perceived as very loud. Paralysis of the stapedius muscle may result when the nerve to the stapedius, a branch of the facial nerve, is damaged, or when the facial nerve itself is damaged before the nerve to stapedius branches. In cases of Bell's palsy, a unilateral paralysis of the facial nerve, the stapedius is paralyzed and hyperacusis may result.
Stapedius muscle | Clinical significance
The anular ligament, a ring-like structure that forms a seal between the end of the stapes and the rim of the vestibular foramen, was probably held in place by cartilage. The transfer of sound between the thin bony plate and the vestibular foramen in "Glanosuchus" was not as effective as it is in mammals, meaning that the animal had a less acute sense of hearing.
Glanosuchus | Hearing
Hearing loss in Treacher Collins syndrome is caused by deformed structures in the outer and middle ear. The hearing loss is generally bilateral with a conductive loss of about 50-70 dB. Even in cases with normal auricles and open external auditory canals, the ossicular chain is often malformed. Attempts to surgically reconstruct the external auditory canal and improve hearing in children with TCS have not yielded positive results. Auditory rehabilitation with bone-anchored hearing aids (BAHAs) or a conventional bone conduction aid has proven preferable to surgical reconstruction.
Treacher Collins syndrome | Hearing loss
However, other patients are also susceptible to conductive losses, similar to nonsyndromic cleft patients (Peterson-Falzone "et al.", 2001).
Hearing loss with craniofacial syndromes | Stickler syndrome
On radiographic images, the otic capsule is the most dense 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 normally dense enchondral bone is replaced by haversian bone, a spongy and vascular matrix that results in sensorineural hearing loss due to compromise of the conductive capacity of the inner ear ossicles. This results in hypodensity on CT, with the portion first affected usually being the "fissula ante fenestram".
Bony labyrinth | Introduction
The stapedius dampens the vibrations of the stapes by pulling on the neck of that bone. As one of the muscles involved in the acoustic reflex it prevents excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear.
Stapedius muscle | Function
The stapes transmits sound waves to the inner ear through the oval window, a flexible membrane separating the air-filled middle ear from the fluid-filled inner ear. The round window, another flexible membrane, allows for the smooth displacement of the inner ear fluid caused by the entering sound waves.
Hearing | Middle ear
The stapes remained in contact with the quadrate bone, but functioned as auditory ossicles rather than supports for the brain case. As a result, the quadrate bones of therapsids likely had a dual function in both the jaw joint and auditory system.
Evolution of mammalian auditory ossicles | Early therapsid jaws and ears
The ability of the tympanum and stapes to effectively transmit vibrations is called impedance matching. Early tetrapods like temnospondyls have thick stapes with poor impedance matching, so it is now thought that they were not used for hearing. Instead, these thick stapes may have functioned to support the tissue that covers the otic notch. Early temnospondyls, like "Dendrerpeton", could not hear airborne sound but would have been able to detect vibration in the ground. Later temnospondyls like "Doleserpeton" had otic regions adapted to hearing. "Doleserpeton" has a structure in the inner ear called the perilymphatic duct, which is also seen in frogs and is associated with hearing.
Temnospondyli | Hearing
Blood supply and innervation The superficial temporal and posterior auricular arteries preserve the arterial blood supply of the external ear. The sensory innervation involves the front and back (anterior and posterior) branches of the greater auricular nerve, and is reinforced by the auricular temporal and lesser occipital nerves. The auricular branch of the vagus nerves supplies a portion of the posterior wall of the external auditory canal. Otoplastic praxis The support framework of the reconstructed pinna must be more rigid than the natural cartilage framework of a normal ear, in order for it to remain of natural size, proportion, and contour.
Otoplasty | Surgical anatomy of the external ear
The stapes is commonly described as having been discovered by the professor Giovanni Filippo Ingrassia in 1546 at the University of Naples, although this remains the nature of some controversy, as Ingrassia's description was published posthumously in his 1603 anatomical commentary '. Spanish anatomist Pedro Jimeno is first to have been credited with a published description, in ' (1549). The bone is so-named because of its resemblance to a stirrup (), an example of a late Latin word, probably created in mediaeval times from "to stand" (), as stirrups did not exist in the early Latin-speaking world.
Stapes | History
These are the most unusual of the braincase bones, and were previously misidentified as stapes. While they are not stapes, it is difficult to be certain what they are. As mentioned, they are sutured to the tubera basioccipitalia, and so could not have moved freely, meaning that they were not bones for the transmission of sound in this manner. Medially, they are sutured to the posterodorsal margins of the tubera basioccipitalia by a strongly serrate and partially intergrown suture. The posterior surface of this forms a steeply inclined trough running from the suture to the distal extremity of the paraoccipital process.
Phantomosaurus | Opisthotic bones
Comparisons have shown stapedotomy to yield either as good or better results than stapedectomy (measured by hearing improvement and reduction in the air-bone hearing gap, and especially at higher sound frequencies), and to be less prone to complications. In particular, stapedotomy procedure greatly reduces the chance of a perilymph fistula (leakage of cochlear fluid). Stapedotomy, like stapedectomy, can be successful in the presence of sclerotic adhesions (tissue growths abnormally linking the bones to the tympanic cavity), provided the adhesions are removed during surgery. However, the adhesions may recur over time. The stapedotomy method is not applicable in those relatively rare cases that involve scleroris of the entire ossicular chain.
Stapedectomy | Stapedectomy vs. stapedotomy
This gain is a form of impedance matching – to match the soundwave travelling through air to that travelling in the fluid–membrane system. At the base of the cochlea, each "duct" ends in a membranous portal that faces the middle ear cavity: The "vestibular duct" ends at the oval window, where the footplate of the stapes sits. The footplate vibrates when the pressure is transmitted via the ossicular chain. The wave in the perilymph moves away from the footplate and towards the helicotrema. Since those fluid waves move the cochlear partition that separates the ducts up and down, the waves have a corresponding symmetric part in perilymph of the "tympanic duct", which ends at the round window, bulging out when the oval window bulges in.
Cochlea | Hearing
Within mammals and other synapsids the columella has evolved into the stapes, a homologous bone within the newly evolved inner ear. As the tympanic cavity evolved to reduce in size, the columella shortened in length. The stirrup-shaped articular processes of the columella inspired a new name for this auditory ossicle, the stapes. The auditory ossicles continue to function in conducting transmitting sound through the auditory pathway; however, they have lost their function in conducting low frequency ground vibrations. Later-arising reptiles with columella likely evolved stronger limbs and a more crawling posture, which removed the body from the ground and prevented the transmission of ground-conducted sounds.
Columella (auditory system) | Homology in mammals
Tympanometry measures the peak pressure (TPP) and peak-compensated static admittance ("Y") of the middle ear at the eardrum. As the stapes is ankylosed in otosclerosis, the lateral end of the ossicular chain may still be quite mobile. Therefore, otosclerosis may only slightly reduce the admittance, resulting in either a shallow tympanogram (type A), or a normal tympanogram (type A). Otosclerosis increases in the stiffness of the middle-ear system, raising its resonant frequency. This can be quantified using multi-frequency tympanometry. Thus, a high resonant-frequency pathology such as otosclerosis can be differentiated from low resonant-frequency pathologies such as ossicular discontinuity. In the absence of a pathology, a loud sound (generally greater than 70 dB above threshold) causes the stapedius muscle to contract, reducing the admittance of the middle ear and softening the perceived loudness of the sound.
Otosclerosis | Audiometry
Conductive hearing loss may occur due to otitis media.
18p- | Hearing
The loss of hearing, when it is caused by neural loss, cannot presently be cured. Instead, its effects can be mitigated by the use of audioprosthetic devices, i.e. hearing assistive devices such as hearing aids and cochlear implants. In a clinical setting, this management is offered by otologists and audiologists.
Hearing | Management
Its stapes is also a better transmitter of sound. The hearing system of "Doleserpeton" and related temnospondyls was able to detect airborne sound and may have been ancestral to that of living amphibians.
Temnospondyli | Hearing
Sounds are transmitted via a receiver attached from the arm of the spectacles which are fitted firmly behind the boney portion of the skull at the back of the ear, (mastoid process) by means of pressure, applied on the arm of the spectacles. The sound is passed from the receiver on the arm of the spectacles to the inner ear (cochlea), via the bony portion. The process of transmitting the sound through the bone requires a great amount of power. Bone conduction aids generally have a poorer high pitch response and are therefore best used for "conductive hearing losses" or where it is impractical to fit standard hearing aids.
Hearing aid | Bone conduction spectacles
This species is likely now extinct.
Theliderma stapes | Conservation
While formerly, preservation of hearing during treatment was very unlikely, the newer techniques of microsurgery and stereotactic radiotherapy have enabled the preservation of functional hearing in the majority of cases. Overall, 60-66% of persons treated for AR preserve their hearing. Likelihood of preserving hearing is correlated with better hearing pre-treatment, and smaller size of tumor. If preservation of hearing is an important goal, the choice of surgical approach may be different. Even in those with functional hearing following surgery or radiotherapy, hearing may decline for years afterward.
Vestibular schwannoma | Hearing loss
These can be on a soft or hard headband or can be inserted surgically, a bone anchored hearing aid, of which there are several types. Conventional air conduction hearing aids can also be used.
Conductive hearing loss | Management
Inward displacement (negative peak pressure on an audiogram) is suggestive of high, and outward of normal or low ICP. The direction and magnitude of TMD, however, depend not only on the initial position of stapes but also on numerous other factors that affect the acoustic impedance (integrity of the eardrum, condition of the ossicles, patency of the Eustachian tube, pressure and eventual presence of fluid or other masses in the middle ear) or the strength of the acoustic reflex (physiological variability of the reflex threshold, functional integrity of the cochlear and facial nerves, degree of eventual sensory hearing loss). In addition, the assumption that the pressure of perilymph is equal to ICP does not hold if the patency of the cochlear aqueduct is compromised, which is often the case in elderly subjects.
Non-invasive measurement of intracranial pressure | Tympanic membrane displacement
Auditory canal decompression is another surgical technique that can prolong usable hearing when a vestibular schwannoma has grown too large to remove without damage to the cochlear nerve. In the IAC (internal auditory canal) decompression, a middle fossa approach is employed to expose the bony roof of the IAC without any attempt to remove the tumor. The bone overlying the acoustic nerve is removed, allowing the tumour to expand upward into the middle cranial fossa. In this way, pressure on the cochlear nerve is relieved, reducing the risk of further hearing loss from direct compression or obstruction of vascular supply to the nerve.
Neurofibromatosis type II | Surgery
Individuals with Treacher Collins syndrome often have both cleft palate and hearing loss, in addition to other disabilities. Hearing loss is often secondary to absent, small or unusually formed ears (microtia) and commonly results from malformations of the middle ear. Researchers have found that most patients with Treacher Collins syndrome have symmetric external ear canal abnormalities and symmetrically dysmorphic or absent ossicles in the middle ear space. Inner ear structure is largely normal. Most patients show a moderate hearing impairment or greater, and the type of loss is generally a conductive hearing loss. Patients with Treacher Collins syndrome exhibit hearing losses similar to those of patients with malformed or missing ossicles (Pron "et al.", 1993).
Hearing loss with craniofacial syndromes | Treacher Collins syndrome
The displacement of the basilar membrane is calculated from the displacement of the stapes and the AHU is then determined by measuring the total displacement of the waves at 23 different locations on the organ of Corti in the inner ear. The effect of the impulse sound can be displayed to create a visual representation of the damage process as it occurs.
Auditory Hazard Assessment Algorithm for Humans | Operation
Management falls into three modalities: surgical treatment, pharmaceutical treatment, and supportive, depending on the nature and location of the specific cause. In cases of infection, antibiotics or antifungal medications are an option. Some conditions are amenable to surgical intervention such as middle ear fluid, cholesteatoma, and otosclerosis. If conductive hearing loss is due to head trauma, surgical repair is an option. If absence or deformation of ear structures cannot be corrected, or if the patient declines surgery, hearing aids which amplify sounds are a possible treatment option. Bone conduction hearing aids are useful as these deliver sound directly, through bone, to the cochlea or organ of hearing bypassing the pathology.
Conductive hearing loss | Management
Note: "The complete anatomy of the human ear is extensive, and can be divided into the inner ear and outer ear. The remainder of this article mainly references the cochlea, outer hair cells, and organ of Corti." In general, structural damages to any anatomical part of the human ear can cause hearing-related problems. Usually, minor bending of the stereocilia of the inner ear is associated with temporary hearing loss and is involved in auditory fatigue. Complete loss of the stereocilia causes permanent hearing damage and is more associated with noise-induced hearing loss and other auditory diseases. The outer hair cells, or OHCs, can be thought of as microamplifiers that provide stimulation to the inner hair cells.
Auditory fatigue | Affected anatomy
Recurrent otitis media is frequently associated with proximal 18q- and, in some cases, may cause conductive hearing loss. This may be resolved with the placement of PE tubes.
Proximal 18q- | ENT
Once diagnosed, the gap in the temporal bone can be repaired by surgical resurfacing of the affected bone or plugging of the superior semicircular canal. These techniques are performed by accessing the site of the dehiscence either via a middle fossa craniotomy or via a canal drilled through the transmastoid bone behind the affected ear. Bone cement has been the material most often used, in spite of its tendency to slippage and resorption, and a consequent high failure rate; recently, soft tissue grafts have been substituted.
Superior canal dehiscence syndrome | Treatment
Individuals with sensorineural hearing loss are believed to have a local lesion in the auditory segment of the inner ear, known as the cochlea. The biological mechanism for this is currently unknown as well.
Otodental syndrome | Mechanism
The dorsal process of the stapes in "Theriognathus" is greatly reduced or entirely absent. The dentary is short, shaped like a banana, and continuously tapers anteriorly to a narrow edge. The dentarys’ lateral surface is smooth. The posterodorsal terminal end of the coronoid process is more rounded, and the dorsal extent terminates below the middle of the orbit in adults. The postdentary bones are reduced to form a free standing coronoid process. The reflected lamina is spade shaped and does not extend below the dentary The area between left and right dentaries remains relatively long and narrow just posterior to symphyseal region.
Theriognathus | Lower jaw
This approach is in a slightly different incision location and is utilized primarily for the purpose of hearing preservation in patients with small tumors, typically confined to the internal auditory canal. A small window of bone is removed above the ear canal to allow exposure of the tumor from the upper surface of the internal auditory canal, preserving the inner ear structures.
Vestibular schwannoma | Middle fossa approach
The quality of the representation of a sound in the auditory nerve is limited by refractoriness, adaptation, saturation, and reduced synchronization (phase locking) at high frequencies, as well as by the stochastic nature of actions potentials. However, the auditory nerve contains thousands of fibers. Hence, despite these limiting factors, the properties of sounds are reasonably well represented in the "population" nerve response over a wide range of levels and audio frequencies (see Volley Theory). The coding of temporal information in the auditory nerve can be disrupted by two main mechanisms: reduced synchrony and loss of synapses and/or auditory nerve fibers.
Temporal envelope and fine structure | Models of impaired processing
The stapes, the bone transmitting sound waves from the eardrum to the middle ear, is elongated and not pierced by a foramen. Pterygoid teeth are typically lacking.
Ichthyosaur | Skull
Caudal to what will eventually become the stapes, Reichert's cartilage also forms the styloid process of the temporal bone. The cartilage between the hyoid bone and styloid process will not remain as development continues, but its perichondrium will eventually form the stylohyoid ligament.
Pharyngeal arch | Reichert's cartilage
Patients with malformations are not always suitable for reconstructive surgery. Treacher Collins syndrome patients may have significant malformations with ossicular defects and an abnormal route of the facial nerve. These structures, as well as the inner ear, could be in danger at surgery. Patients with Down syndrome may have a narrow ear canal and middle ear malformation leading to impaired hearing. Some part of the cognitive delay seen in these children may be partly due to their poor hearing. The surgery can only take place once the skull is at least 2.5 mm thick. Children who suffer certain syndromes may have a slighter build, thinner bone, or unusual anatomy.
Bone-anchored hearing aid | Malformations
There is no simple clinical means of identifying which ears will deteriorate to accumulate keratin debris in the pars tensa retraction, a phenomenon that is not influenced by age. In children, the pars tensa retraction may remain unchanged while the pars flaccida deteriorates to form cholesteatoma.
Tympanic membrane retraction | Natural history
The stereocilia (hair cells) of the inner ear can become subjected to bending from loud noises. Because they are not regeneratable in humans, any major damage or loss of these hair cells leads to permanent hearing impairment and other hearing-related diseases. Outer hair cells serve as acoustic amplifiers for stimulation of the inner hair cells. Outer hair cells respond primarily to low-intensity sounds.
Listener fatigue | Associated anatomy
Otosclerosis is a condition where one or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule in the bony labyrinth. This condition affects one of the ossicles (the stapes) resulting in hearing loss, tinnitus, vertigo or a combination of symptoms. The term otosclerosis is something of a misnomer. Much of the clinical course is characterized by lucent rather than sclerotic bony changes, so the disease is also known as otospongiosis.
Otosclerosis | Introduction
The vestibule is somewhat oval in shape, but flattened transversely; it measures about 5 mm from front to back, the same from top to bottom, and about 3 mm across. In its lateral or tympanic wall is the oval window (fenestra vestibuli), closed, in the fresh state, by the base of the stapes and annular ligament. On its medial wall, at the forepart, is a small circular depression, the recessus sphæricus, which is perforated, at its anterior and inferior part, by several minute holes (macula cribrosa media) for the passage of filaments of the acoustic nerve to the saccule; and behind this depression is an oblique ridge, the crista vestibuli, the anterior end of which is named the pyramid of the vestibule.
Vestibule of the ear | Structure
However, they were too incompletely preserved to estimate the light sensitivity of the eyes. The footplates of the bony stapes are large, associated with hearing low-frequency sounds underground, although its inner-ear is not as specialised as "Kawingasaurus".
Kembawacela | Burrowing
The "stapes" (stirrup) ossicle bone of the middle ear transmits vibrations to the "fenestra ovalis" (oval window) on the outside of the cochlea, which vibrates the perilymph in the "vestibular duct" (upper chamber of the cochlea). The ossicles are essential for efficient coupling of sound waves into the cochlea, since the cochlea environment is a fluid–membrane system, and it takes more pressure to move sound through fluid–membrane waves than it does through air; a pressure increase is achieved by the area ratio of the tympanic membrane to the oval window, resulting in a pressure gain of about 20× from the original sound wave pressure in air.
Cochlea | Hearing
In the tetrapod and higher clades from the lower-middle Famennian there are several defining changes on the basis of anatomy of "Ichthyostega", "Tulerpeton", and "Acanthostega". In the cranium, there is a stapes derived from the hyomandibular of fishes; a single bilateral pair of nasal bones, and a fenestra ovalis in the otic capsule of the braincase. The opening of the otic wall of the braincase can be considered a paedomorphic feature for tetrapods and is linked to the stapes functionally. The stapes was thought to be just a structural support between the palate and the stapedial plate of the braincase.
Skeletal changes of organisms transitioning from water to land | Head changes in aquatic tetrapods
If the reconstructed pinna framework were as structurally delicate as the cartilage framework of a natural pinna, its anatomic verisimilitude as an ear would gradually be eroded by a combination of the pressure of the tight skin-envelope in the temporal region of the head, and of the pressure of the progressive contracture of the surgical scar(s).
Otoplasty | Surgical anatomy of the external ear
Early labyrinthodont groups had massive stapes, likely primarily anchoring the brain case to the skull roof. It is a question of some doubt whether early terrestrial labyrinthodonts had the stapes connected to a tympanum covering their otic notch, and if they had an aerial sense of hearing at all. The tympanum in anurans and amniotes appear to have evolved separately, indicating most, if not all, labyrinthodonts were unable to pick up airborne sound.
Labyrinthodontia | Sensory apparatus
It is occupied by the base of the stapes, the circumference of which is fixed by the annular ligament to the margin of the foramen.
Oval window | Introduction
Several psychophysical studies have shown that older people with normal hearing and people with sensorineural hearing loss often show impaired performance for auditory tasks that are assumed to rely on the ability of the monaural and binaural auditory system to encode and use TFS cues, such as: discrimination of sound frequency, discrimination of the fundamental frequency of harmonic sounds, detection of FM at rates below 5 Hz, melody recognition for sequences of pure tones and complex sounds, lateralization and localization of pure tones and complex tones, and segregation of concurrent harmonic sounds (such as speech sounds). However, it remains unclear to which extent deficits associated with hearing loss reflect poorer TFS processing or reduced cochlear frequency selectivity.
Temporal envelope and fine structure | Psychoacoustical aspects
These findings therefore imply that the loss of music perception in auditory agnosia is because of damage to the medial anterior STG. In contrast to the association of amusia specific to recognition of melodies (amelodia) with the temporal pole, posterior STG damage was associated with loss of rhythm perception (arryhthmia). Conversely, in two patients rhythm perception was intact, while recognition/discrimination of musical segments was impaired. Amusia also dissociates in regard to enjoyment from music. In two reports, amusic patients, who weren't able to distinguish musical instruments, reported that they still enjoy listening to music. On the other hand, a patient with left hemispheric damage in the amygdala was reported to perceive, but not enjoy, music.
Auditory agnosia | Amusia
A patient with a unilateral conductive hearing loss would hear the tuning fork loudest in the affected ear. This is because the ear with the conductive hearing loss is only receiving input from the bone conduction and no air conduction, and the sound is perceived as louder in that ear. This finding is because the conduction problem of the middle ear (incus, malleus, stapes, and external auditory meatus) masks the ambient noise of the room, while the well-functioning inner ear (cochlea with its basilar membrane) picks the sound up via the bones of the skull, causing it to be perceived as a louder sound in the affected ear.
Weber test | Detection of air conductive hearing loss
This tonotopic degradation is likely to have important implications for speech perception, and can account for degraded coding of vowels following noise-induced hearing loss in which most of the cochlea responds to only the first formant, eliminating the normal tonotopic representation of the second and third formants.
Temporal envelope and fine structure | Neurophysiological aspects
There is no treatment, surgical or otherwise, for sensorineural hearing loss due to the most common causes (age, noise, and genetic defects). For a few specific conditions, surgical intervention can provide a remedy: Surgical and implantable hearing aids are an alternative to conventional external hearing aids. If the ear is dry and not infected, an air conduction aid could be tried; if the ear is draining, a direct bone conduction hearing aid is often the best solution. If the conductive part of the hearing loss is more than 30–35 dB, an air conduction device could have problems overcoming this gap.
Management of hearing loss | Surgery
The stapedius emerges from a pinpoint foramen in the apex of the pyramidal eminence (a hollow, cone-shaped prominence in the posterior wall of the tympanic cavity), and inserts into the neck of the stapes.
Stapedius muscle | Structure
As vibrations compress the bones of the skull, pressure is put on the otic capsule and the membranous labyrinth. This then compresses the scala vestibule into the basilar membrane in the direction toward the scala tympani. A traveling wave is created similar to that created by air conduction signals.
Bone conduction auditory brainstem response | Distortional bone-conduction
Indeed, for the same quantity of bone, different mechanically resistant bone structures may exist (few large trabeculae or numerous thin trabeculae that are mechanically stronger). Actually, bone loss is often accompanied by a deterioration of bone architecture, resulted in a decreased number of trabeculae, increased inter-trabecular distances, and a loss connectivity of the trabecular meshwork. Moreover, reduction of cortical bone thickness and increased porosity accompany trabecular bone loss, and in particular promote the fragility of the femoral neck. Osteoporotic bone is called "porous".
Trabecular bone score | Need for a marker of microarchitecture
If it shows continued growth and becomes life-threatening, or if the hearing is lost over time as the tumor grows, then treatment is undertaken. This strategy has the highest chance of preserving hearing for the longest time possible.
Vestibular schwannoma | Treatment
This output limitation of the bone oscillator is a drawback.
Bone conduction auditory brainstem response | Problems with BCABR
The external ear has lost the pinna (visible ear), but still retains a narrow external auditory meatus. To register sounds, instead, the posterior part of the mandible has a thin lateral wall (the pan bone) fronting a concavity that houses a fat pad. The pad passes anteriorly into the greatly enlarged mandibular foramen to reach in under the teeth and posteriorly to reach the thin lateral wall of the ectotympanic. The ectotympanic offers a reduced attachment area for the tympanic membrane. The connection between this auditory complex and the rest of the skull is reduced—to a single, small cartilage in oceanic dolphins.
Cetacea | Ears
If the periosteum or underlying muscles (frontalis, occipitalis, temporalis) are intact, secondary closure by granulation is possible. Before surgical intervention this was the only option available, as used to treat Robert McGee in 1864. Considering modern aesthetic standards, a better option is the use of split-thickness or full-thickness skin grafts, which is also quicker. When bulk is needed for a better contour a free flap is used, or as shown in the pictures, a regional flap.
Scalp reconstruction | Soft tissue defects
Mutations in this gene have been associated with cone-rod dystrophy with hearing loss.
CEP78 | Clinical
The round window sometimes fails to develop correctly and causes the hearing loss mentioned above. Unfortunately round window malformations are often associated with other ear malformations and the hearing loss can be much more severe. Some types of ear surgery (now generally abandoned) used to leave the round window open to the outside world and covered over the oval window. Sound pressure therefore hit the round window but was shielded from the oval window. It therefore travelled "backwards" around the cochlea but still gave useful hearing as the hair cells were still deflected in the same way. The round window is often used as an approach for cochlear implant surgery.
Round window | Clinical significance
A temporal-bone CT using thin slices makes it possible to diagnose the degree of stenosis and atresia of the external auditory canal, the status of the middle ear cavity, the absent or dysplastic and rudimentary ossicles, or inner ear abnormalities such as a deficient cochlea. Two- and three-dimensional CT reconstructions with VRT and bone and skin-surfacing are helpful for more accurate staging and the three-dimensional planning of mandibular and external ear reconstructive surgery.
Treacher Collins syndrome | CT scan
The transfer function of this complex mechanical system under physiological conditions is modulated by the action of two small muscles of the middle ear, the tensor tympani, and stapedius. The tensor tympani arises from the cartilaginous portion of the auditory tube and the osseous canal of the sphenoid and, having sharply bent over the extremity of the septum, attaches to the manubrium of the malleus (hammer); its contraction pulls the malleus medially, away from the tympanic membrane, which tenses the membrane. The stapedius, which emerges from the posterior wall of the tympanic cavity of the middle ear and inserts into the neck of the stapes (stirrup), prevents excess movements of the stapes by pulling it away from the oval window.
Non-invasive measurement of intracranial pressure | Tympanic membrane displacement
The principal idea of the selection and fitting of the hearing instrument was based on the assumption that amplitudes of the brainstem potentials were directly related to loudness perception. Under this assumption, the amplitudes of brainstem potentials stimulated by the hearing devices should exhibit close-to-normal values. ABR thresholds do not necessarily improve in the aided condition. ABR can be an inaccurate indicator of hearing aid benefit due to difficulty processing the appropriate amount of fidelity of the transient stimuli used to evoke a response. Bone conduction ABR thresholds can be used if other limitations are present, but thresholds are not as accurate as ABR thresholds recorded through air conduction.
Auditory brainstem response | Hearing aid fittings
Persons with Pierre Robin sequence (PRS) are at greater risk for hearing impairment than persons with cleft lip and/or palate without PRS. One study showed an average of 83% hearing loss in PRS, compared to 60% in cleft individuals without PRS (Handzic "et al.", 1995). Similarly, PRS individuals typically exhibit conductive, bilateral hearing losses that are greater in degree than in cleft individuals without PRS. Middle ear effusion is generally apparent, with no middle ear or inner ear malformations. Accordingly, management by ear tubes (myringotomy tubes) is often effective and may restore normal levels of hearing (Handzic "et al.", 1995).
Hearing loss with craniofacial syndromes | Pierre Robin sequence
Bell's palsy can result from inflammation of the facial nerve where it leaves the skull at the stylomastoid foramen. Patients with Bell's palsy appear with facial drooping on the affected side.
Stylomastoid foramen | Clinical relevance
In 1995, Glasscock et al. published a 25-year single-centre review of over 900 patients who underwent stapedectomy and stapedotomy and found complications rates as follows: reparative granuloma 1.3%, tympanic membrane perforation 1.0%, total sensorineural hearing loss 0.6%, partial sensorineural hearing loss 0.3%, and vertigo 0.3%. In this series, there was no incidence of facial nerve paralysis or tinnitus.
Stapedectomy | Complications
John Joseph Shea Jr. (September 4, 1924 – February 8, 2015) was an American medical doctor, professor and surgeon. He attended Christian Brothers High School, Memphis, Tennessee, the University of Notre Dame and Harvard Medical School. He performed the first successful reconstructive stapedectomy in May, 1956. The patient was a 54-year-old housewife with conductive hearing loss so severe that she could no longer hear at all, even with a hearing aid. Shea removed the stapes, covered the oval window opening with a vein graft removed from the back of the patient's hand, and inserted a prosthesis to replace the diseased stapes bone.
John J. Shea Jr. | Introduction
In advanced cynodonts, including the mammaliaforms, have lost the quadratojugal, with the diminutive quadrate connecting to the stapes to function as a hearing structure. In modern mammals, the quadrate bone evolves to become the incus, one of the ossicles of the middle ear. This is an apomorphy of the mammalian clade, and is used to identify the fossil transition to mammals.
Quadratojugal bone | In mammals
He performed studies on the functionality of the Eustachian tube and of the tympanic membrane and tried to restore attempts, the tympanoplasty. When St. Mary’s Hospital was founded in Paddington, he a became an aural surgeon and a lecturer on ear diseases — his course of clinical lectures being published in 1855 and 1866. During this time period he composed two major works: "A Descriptive Catalogue of Preparations Illustrative of the Diseases of the Ear" (1857), and "The Diseases of the Ear: Their Nature, Diagnosis and Treatment" (1860). From his many dissections of "deaf ears", he studied ankylosis of the stapes.
Joseph Toynbee | Career
It has also recently been used as a site to place middle ear implantable hearing aid transducers. This work has been publicised by Prof. Vittorio Colletti in Verona.
Round window | Clinical significance
As with air-conduction stimuli, thresholds for bone-conduction stimuli should be obtained using tone burst stimuli Stapells is one researcher who reported on the accuracy of using tone bursts with BC ABR to estimate cochlear hearing sensitivity. Stapells and Ruben, in 1989, demonstrated bone-conduction tone burst ABRs in infants with conductive hearing loss. Hatton, Janssen and Stapells (2012) present bone-conduction tone burst ABR results in infants with normal bone-conduction thresholds or sensorineural hearing loss. BC ABR methods are described in 2010 review chapter by Stapells.
Bone conduction auditory brainstem response | BCABR with tone bursts
The hair cells have a hair bundle at the apical surface of the cell. The hair bundle consists of an array of actin-based stereocilia. Each stereocilium inserts as a rootlet into a dense filamentous actin mesh known as the cuticular plate. Disruption of these bundles results in hearing impairments and balance defects.
Inner ear | Microanatomy