Otosclerosis
Encyclopedia
Otosclerosis is an abnormal growth of bone near the middle ear
. It can result in hearing loss.
(CHL) whereby sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear
(cochlea
). This usually will begin in one ear but will eventually affect both ears with a variable course. On audiometry
, the hearing loss is characteristically low-frequency, with higher frequencies being affected later. Sensorineural hearing loss
(SNHL) has also been noted in patients with otosclerosis; this is usually a high-frequency loss, and usually manifests late in the disease. The causal link between otosclerosis and SNHL remains controversial.
Approximately 0.5% of the population will eventually be diagnosed with otosclerosis. Post mortem studies show that as many as 10% of people may have otosclerotic lesions of their temporal bone, but apparently never had symptoms warranting a diagnosis. Caucasians are the most affected race, with the prevalence in the Black and Asian populations being much lower. In clinical practice otosclerosis is encountered about twice as frequently in females as in males, but this does not reflect the true sex ratio. When families are investigated it is found that the condition is only slightly more common in women. Usually noticeable hearing loss begins at middle-age, but can start much sooner. The hearing loss was believed to grow worse during pregnancy; but research shows that neither pregnancy nor breastfeeding may aggravate otosclerosis.
and the degree of expression is so highly variable that it may be difficult to detect an inheritance pattern. Most of the implicated genes are transmitted in an autosomal dominant fashion. One genome-wide analysis associates otosclerosis with variation in RELN
gene.
Loci include:
, but they are not thought to be otherwise related. Histopathologic studies have all been done on cadaveric temporal bones, so only inferences can be made about progression of the disease histologically. It seems that the lesions go through an active “spongiotic” / hypervascular phase before developing into “sclerotic” phase lesions. There have been many genes and proteins identified that, when mutated, may lead to these lesions. Also there is mounting evidence that measles virus is present within the otosclerotic foci, implicating an infectious etiology (this has also been noted in Paget’s Disease).
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”).
SNHL in otosclerosis is controversial. Over the past century, leading otologists and neurotologic researchers have argued whether the finding of SNHL late in the course of otosclerosis is due to otosclerosis or simply to typical presbycusis
. There are certainly a few well documented instances of sclerotic lesions directly obliterating sensory structures within the cochlea and spiral ligament, which have been photographed and reported post-mortem. Other supporting data includes a consistent loss of cochlear hair cells in patients with otosclerosis; these cells being the chief sensory organs of sound reception. A suggested mechanism for this is the release of hydrolytic enzymes into the inner ear structures by the spongiotic lesions.
clinical findings, which include progressive conductive
hearing loss, a normal tympanic membrane, and no evidence
of middle ear inflammation. The cochlear promontory may have a faint pink tinge reflecting
the vascularity of the lesion, referred to as the Schwartze sign.
Conductive hearing loss is usually secondary to impingement
of abnormal bone on the stapes footplate. This involvement
of the oval window forms the basis of the name fenestral
otosclerosis. The most common location of involvement of
otosclerosis is the bone just anterior to the oval window at a
small cleft known as the fissula ante fenestram. The fissula is
a thin fold of connective tissue extending through the endochondral
layer, approximately between the oval window and
the cochleariform process, where the tensor tympani tendon
turns laterally toward the malleus.
Imaging is usually not pursued in those with
uncomplicated conductive hearing loss and characteristic
clinical findings. Those with only conductive hearing loss
are often treated medically or with surgery without imaging.
The diagnosis may be unclear clinically in cases
of sensorineural or mixed hearing loss and may become apparent
only on imaging. Therefore, imaging is often performed
when the hearing loss is
sensorineural or mixed. The mechanism of sensorineural
hearing loss in otosclerosis is less well understood. It may result
from direct injury to the cochlea and spiral ligament from
the lytic process or from release of proteolytic enzymes into
the cochlea.
A high-resolution CT shows very subtle bone findings. However, CT is usually not needed prior to surgery.
Otosclerosis on CT can be graded using the grading system suggested by Symons and Fanning. Grade 1, solely fenestral; grade 2, patchy localized cochlear disease (with or without
fenestral involvement) to either the basal cochlear turn (grade 2A), or the middle/apical turns (grade
2B), or both the basal turn and the middle/apical turns (grade 2C); and grade 3, diffuse confluent
cochlear involvement (with or without fenestral involvement).
s (more recently including bone-conduction hearing aids) and a surgery called a stapedectomy
. Hearing aids are usually very effective early in the course of the disease, but eventually a stapedectomy (or more frequently a variant called the stapedotomy) may be required for definitive treatment. Early attempts at hearing restoration via the simple freeing 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. The success rate of either surgery depends greatly on the skill and the familiarity with the procedure of the surgeon. However, comparisons have shown stapedotomy to yield results at least as good as stapedectomy, with fewer complications, and thus stapedotomy is preferred under normal circumstances.
Other less successful treatments involve pharmaceuticals or orally ingested supplements. One is fluoride administration, which theoretically becomes incorporated into bone and inhibits otosclerotic progression. This treatment cannot reverse conductive hearing loss, but may slow the progression of both the conductive and sensorineural components of the disease process. Otoflour is one such widely used medicine, comprising sodium fluoride. Recently, some success has been claimed with a second such treatment, bisphosphonate
medications that inhibit bone destruction. However, these early reports are based on non-randomized case studies that do not meet standards of clinical trials. There are numerous side-effects to both pharmaceutical treatments, including occasional stomach upset, allergic itching, and increased joint pains which can lead to arthritis. In the worst case, bisphosphonates may lead to osteonecrosis of the auditory canal itself. Finally, neither approach has been proven to be beneficial after the commonly preferred method of surgery has been undertaken.
Victorian journalist Harriet Martineau
gradually lost her hearing during her young life, and later medical historians have diagnosed her with probably suffering from otosclerosis as well.
Howard Hughes
the pioneering American aviator, engineer, industrialist, and film producer also suffered from otosclerosis. Frankie Valli
, lead singer of The Four Seasons
, suffered from it in the 1970s, forcing him to "sing from memory" in the latter part of the decade (surgery restored most of his hearing by 1980). Tampa Bay Lightning
forward Steve Downie
suffers from otosclerosis.
Alexandra of Denmark
, Queen of the United Kingdom suffered from it.
Adam Savage
, host of MythBusters
, uses a hearing aid due to otosclerosis.
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
. It can result in hearing loss.
Clinical description
Otosclerosis can result in conductive and/or sensorineural hearing loss. The primary form of hearing loss in otosclerosis is conductive hearing lossConductive hearing loss
Conductive hearing loss occurs when there is a problem conducting sound waves anywhere along the route through the outer ear, tympanic membrane , or middle ear ....
(CHL) whereby sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
(cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
). This usually will begin in one ear but will eventually affect both ears with a variable course. On audiometry
Audiometry
Audiometry is the testing of hearing ability, involving thresholds and differing frequencies. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or...
, the hearing loss is characteristically low-frequency, with higher frequencies being affected later. Sensorineural hearing loss
Sensorineural hearing loss
Sensorineural hearing loss is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve , the inner ear, or central processing centers of the brain....
(SNHL) has also been noted in patients with otosclerosis; this is usually a high-frequency loss, and usually manifests late in the disease. The causal link between otosclerosis and SNHL remains controversial.
Approximately 0.5% of the population will eventually be diagnosed with otosclerosis. Post mortem studies show that as many as 10% of people may have otosclerotic lesions of their temporal bone, but apparently never had symptoms warranting a diagnosis. Caucasians are the most affected race, with the prevalence in the Black and Asian populations being much lower. In clinical practice otosclerosis is encountered about twice as frequently in females as in males, but this does not reflect the true sex ratio. When families are investigated it is found that the condition is only slightly more common in women. Usually noticeable hearing loss begins at middle-age, but can start much sooner. The hearing loss was believed to grow worse during pregnancy; but research shows that neither pregnancy nor breastfeeding may aggravate otosclerosis.
Genetics
The disease can be considered to be heritable, but its penetrancePenetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant of a gene that also express an associated trait . In medical genetics, the penetrance of a disease-causing mutation is the proportion of individuals with the mutation who exhibit clinical symptoms...
and the degree of expression is so highly variable that it may be difficult to detect an inheritance pattern. Most of the implicated genes are transmitted in an autosomal dominant fashion. One genome-wide analysis associates otosclerosis with variation in RELN
Reelin
Reelin is a large secreted extracellular matrix protein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the...
gene.
Loci include:
| Name | OMIM | Locus |
|---|---|---|
| OTSC1 | 15q26.1 | |
| OTSC2 | 7q | |
| OTSC3 | 6p | |
| OTSC4 | 16q | |
| OTSC5 | 3q22-q24 | |
| OTSC7 | 6q13 | |
| OTSC8 | 9p13.1-q21.11 |
Pathophysiology
The pathophysiology of otosclerosis is complex. The key lesions of otosclerosis are multifocal areas of sclerosis within the endochondral temporal bone. These lesions share some characteristics with Paget’s DiseasePaget's disease of bone
Paget's disease is a chronic disorder that can result in enlarged and misshapen bones. The excessive breakdown and formation of bone tissue causes affected bone to weaken, resulting in pain, misshapen bones, fractures, and arthritis in the joints near the affected bones...
, but they are not thought to be otherwise related. Histopathologic studies have all been done on cadaveric temporal bones, so only inferences can be made about progression of the disease histologically. It seems that the lesions go through an active “spongiotic” / hypervascular phase before developing into “sclerotic” phase lesions. There have been many genes and proteins identified that, when mutated, may lead to these lesions. Also there is mounting evidence that measles virus is present within the otosclerotic foci, implicating an infectious etiology (this has also been noted in Paget’s Disease).
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
Oval window
The oval window is a membrane-covered opening which leads from the middle ear to the vestibule of the inner ear.Vibrations that come into contact with the tympanic membrane travel through the three ossicles and into the inner ear...
of the cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
. 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”).
SNHL in otosclerosis is controversial. Over the past century, leading otologists and neurotologic researchers have argued whether the finding of SNHL late in the course of otosclerosis is due to otosclerosis or simply to typical presbycusis
Presbycusis
Presbycusis, or age-related hearing loss, is the cumulative effect of aging on hearing. Also known as presbyacusis, it is defined as a progressive bilateral symmetrical age-related sensorineural hearing loss. The hearing loss is most marked at higher frequencies...
. There are certainly a few well documented instances of sclerotic lesions directly obliterating sensory structures within the cochlea and spiral ligament, which have been photographed and reported post-mortem. Other supporting data includes a consistent loss of cochlear hair cells in patients with otosclerosis; these cells being the chief sensory organs of sound reception. A suggested mechanism for this is the release of hydrolytic enzymes into the inner ear structures by the spongiotic lesions.
Diagnosis
Otosclerosis is traditionally diagnosed by characteristicclinical findings, which include progressive conductive
hearing loss, a normal tympanic membrane, and no evidence
of middle ear inflammation. The cochlear promontory may have a faint pink tinge reflecting
the vascularity of the lesion, referred to as the Schwartze sign.
Conductive hearing loss is usually secondary to impingement
of abnormal bone on the stapes footplate. This involvement
of the oval window forms the basis of the name fenestral
otosclerosis. The most common location of involvement of
otosclerosis is the bone just anterior to the oval window at a
small cleft known as the fissula ante fenestram. The fissula is
a thin fold of connective tissue extending through the endochondral
layer, approximately between the oval window and
the cochleariform process, where the tensor tympani tendon
turns laterally toward the malleus.
Imaging is usually not pursued in those with
uncomplicated conductive hearing loss and characteristic
clinical findings. Those with only conductive hearing loss
are often treated medically or with surgery without imaging.
The diagnosis may be unclear clinically in cases
of sensorineural or mixed hearing loss and may become apparent
only on imaging. Therefore, imaging is often performed
when the hearing loss is
sensorineural or mixed. The mechanism of sensorineural
hearing loss in otosclerosis is less well understood. It may result
from direct injury to the cochlea and spiral ligament from
the lytic process or from release of proteolytic enzymes into
the cochlea.
A high-resolution CT shows very subtle bone findings. However, CT is usually not needed prior to surgery.
Otosclerosis on CT can be graded using the grading system suggested by Symons and Fanning. Grade 1, solely fenestral; grade 2, patchy localized cochlear disease (with or without
fenestral involvement) to either the basal cochlear turn (grade 2A), or the middle/apical turns (grade
2B), or both the basal turn and the middle/apical turns (grade 2C); and grade 3, diffuse confluent
cochlear involvement (with or without fenestral involvement).
Treatment
Treatment of otosclerosis relies on two primary options: hearing aidHearing aid
A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...
s (more recently including bone-conduction hearing aids) and a surgery called a stapedectomy
Stapedectomy
A stapedectomy is a surgical procedure of the middle ear performed to improve hearing. The world's first stapedectomy is credited to Dr. John J.Shea Jr. who performed it in May 1956 on a 54-year-old housewife who could no longer hear even with a hearing aid. Significant contributions to modern...
. Hearing aids are usually very effective early in the course of the disease, but eventually a stapedectomy (or more frequently a variant called the stapedotomy) may be required for definitive treatment. Early attempts at hearing restoration via the simple freeing 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. The success rate of either surgery depends greatly on the skill and the familiarity with the procedure of the surgeon. However, comparisons have shown stapedotomy to yield results at least as good as stapedectomy, with fewer complications, and thus stapedotomy is preferred under normal circumstances.
Other less successful treatments involve pharmaceuticals or orally ingested supplements. One is fluoride administration, which theoretically becomes incorporated into bone and inhibits otosclerotic progression. This treatment cannot reverse conductive hearing loss, but may slow the progression of both the conductive and sensorineural components of the disease process. Otoflour is one such widely used medicine, comprising sodium fluoride. Recently, some success has been claimed with a second such treatment, bisphosphonate
Bisphosphonate
Bisphosphonates are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases...
medications that inhibit bone destruction. However, these early reports are based on non-randomized case studies that do not meet standards of clinical trials. There are numerous side-effects to both pharmaceutical treatments, including occasional stomach upset, allergic itching, and increased joint pains which can lead to arthritis. In the worst case, bisphosphonates may lead to osteonecrosis of the auditory canal itself. Finally, neither approach has been proven to be beneficial after the commonly preferred method of surgery has been undertaken.
Famous patients
The renowned German composer Beethoven was theorized to suffer from otosclerosis, although this is controversial.Victorian journalist Harriet Martineau
Harriet Martineau
Harriet Martineau was an English social theorist and Whig writer, often cited as the first female sociologist....
gradually lost her hearing during her young life, and later medical historians have diagnosed her with probably suffering from otosclerosis as well.
Howard Hughes
Howard Hughes
Howard Robard Hughes, Jr. was an American business magnate, investor, aviator, engineer, film producer, director, and philanthropist. He was one of the wealthiest people in the world...
the pioneering American aviator, engineer, industrialist, and film producer also suffered from otosclerosis. Frankie Valli
Frankie Valli
Frankie Valli is an American musician, most famous as frontman of The Four Seasons. He is well-known for his unusually powerful falsetto singing voice...
, lead singer of The Four Seasons
The Four Seasons (group)
The Four Seasons are an American rock and pop band who became internationally successful in the mid-1960s. The Vocal Group Hall of Fame has stated that the group was the most popular rock band before The Beatles...
, suffered from it in the 1970s, forcing him to "sing from memory" in the latter part of the decade (surgery restored most of his hearing by 1980). Tampa Bay Lightning
Tampa Bay Lightning
The Tampa Bay Lightning are a professional ice hockey team based in Tampa, Florida. They are members of the Southeast Division of the Eastern Conference of the National Hockey League . They have one Stanley Cup championship in their history, in 2003–04. They are often referred to as the...
forward Steve Downie
Steve Downie
Steve Downie is a Canadian professional ice hockey player currently playing for the Tampa Bay Lightning in the National Hockey League.-Playing career:...
suffers from otosclerosis.
Alexandra of Denmark
Alexandra of Denmark
Alexandra of Denmark was the wife of Edward VII of the United Kingdom...
, Queen of the United Kingdom suffered from it.
Adam Savage
Adam Savage
Adam Whitney Savage is an American industrial design and special effects designer/fabricator, actor, educator, and co-host of the Discovery Channel television series MythBusters. His model work has appeared in major films, including Star Wars: Episode II - Attack of the Clones and The Matrix...
, host of MythBusters
MythBusters
MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...
, uses a hearing aid due to otosclerosis.
External links
- NIH/Medline
- NIH/NIDCD
- Otosclerosis Patient Accounts and Support - Patient Support