Sensorineural hearing loss
Encyclopedia
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve
(Cranial nerve VIII), the inner ear
, or central processing centers of the brain
.
The Weber test
, in which a tuning fork is touched to the midline of the forehead, localizes to the normal ear
in people with this condition.
The Rinne test
, which tests air conduction vs. bone conduction is positive (normal), though both bone and air conduction are reduced equally.
Sensorineural hearing loss can be mild, moderate, or severe, including total deafness.
The great majority of human sensorineural hearing loss is caused by abnormalities in the hair cells of the organ of Corti
in the cochlea. There are also very unusual sensorineural hearing impairments that involve the eighth cranial nerve (the vestibulocochlear nerve
) or the auditory portions of the brain. In the rarest of these sorts of hearing loss, only the auditory centers of the brain are affected. In this situation, central hearing loss
, sounds may be heard at normal thresholds, but the quality of the sound perceived is so poor that speech cannot be understood.
Most sensory hearing loss is due to poor hair cell function. The hair cells may be abnormal at birth, or damaged during the lifetime of an individual. There are both external causes of damage, like noise trauma and infection, and intrinsic abnormalities, like deafness genes.
Sensory hearing loss that results from abnormalities of the central auditory system in the brain is called central hearing impairment. Since the auditory pathways cross back and forth on both sides of the brain, deafness from a central cause is unusual.
This type of hearing loss can also be caused by prolonged exposure to very loud noise, for example, being in a loud workplace without hearing protection, or having headphones set to high volumes for a long period.
Sensorineural hearing loss may be congenital or acquired.
and various states have set noise standards to protect people from these adverse health risks. The EPA has identified the level of 70 db(A) for 24 hour exposure as the level necessary to protect the public from hearing loss (EPA, 1974).
Dominant and recessive hearing impairment can be syndromic or nonsyndromic. Recent gene mapping has identified dozens of nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness.
Some medications cause irreversible damage to the ear, and are limited in their use for this reason. The most important group is the aminoglycoside
s (main member gentamicin
).
Various other medications may reversibly affect hearing. This includes some diuretic
s, sildenafil
and NSAIDs, and macrolide
antibiotics.
Extremely heavy hydrocodone
(Vicodin) abuse is known to cause hearing impairment. There has been speculation radio talk show host Rush Limbaugh
's hearing loss was at least in part caused by his admitted addiction to narcotic pain killers, in particular Vicodin and OxyContin
.
[needs citation]
s, which amplify sounds at preset frequencies to overcome a sensorineural hearing loss in that range; or cochlear implant
s, which stimulate the cochlear nerve
directly.
Some research suggests idebenone
alone or combined with vitamin E
may delay the onset of hearing loss or perhaps reverse it. Use of these agents for this purpose is considered experimental now.
Some audiologists and ENTs have reported if severe noise-induced hearing loss (exposures exceeding 140dB) is treated immediately (within 24 hours) with a course of steroids, it can often be almost completely reversed. This, however, is a new field without proven success.
Researchers at the University of Michigan report that a combination of high doses of vitamins A, C, and E, and Magnesium, taken one hour before noise exposure and continued as a once-daily treatment for five days, was very effective at preventing permanent noise-induced hearing loss in animals
Vestibulocochlear nerve
The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
(Cranial nerve VIII), the inner ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
, or central processing centers of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
.
The Weber test
Weber test
The Weber test is a quick screening test for hearing. It can detect unilateral conductive hearing loss and unilateral sensorineural hearing loss...
, in which a tuning fork is touched to the midline of the forehead, localizes to the normal ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
in people with this condition.
The Rinne test
Rinne test
The Rinne test is a hearing test. It compares perception of sounds transmitted by air conduction to those transmitted by bone conduction through the mastoid...
, which tests air conduction vs. bone conduction is positive (normal), though both bone and air conduction are reduced equally.
Sensorineural hearing loss can be mild, moderate, or severe, including total deafness.
The great majority of human sensorineural hearing loss is caused by abnormalities in the hair cells of the organ of Corti
Organ of Corti
The organ of Corti is the organ in the inner ear of mammals that contains auditory sensory cells, or "hair cells."The organ was named after the Italian anatomist Marquis Alfonso Giacomo Gaspare Corti , who conducted microscopic research of the mammaliean auditory system.-Structure and function:The...
in the cochlea. There are also very unusual sensorineural hearing impairments that involve the eighth cranial nerve (the vestibulocochlear nerve
Vestibulocochlear nerve
The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
) or the auditory portions of the brain. In the rarest of these sorts of hearing loss, only the auditory centers of the brain are affected. In this situation, central hearing loss
Central hearing loss
Central hearing loss is a form of sensorineural hearing loss caused by damage to the auditory pathways. When the damage is to the primary auditory cortex, the impairment is called "cortical deafness".- Cortical deafness :...
, sounds may be heard at normal thresholds, but the quality of the sound perceived is so poor that speech cannot be understood.
Most sensory hearing loss is due to poor hair cell function. The hair cells may be abnormal at birth, or damaged during the lifetime of an individual. There are both external causes of damage, like noise trauma and infection, and intrinsic abnormalities, like deafness genes.
Sensory hearing loss that results from abnormalities of the central auditory system in the brain is called central hearing impairment. Since the auditory pathways cross back and forth on both sides of the brain, deafness from a central cause is unusual.
This type of hearing loss can also be caused by prolonged exposure to very loud noise, for example, being in a loud workplace without hearing protection, or having headphones set to high volumes for a long period.
Differential diagnosis
Table 1. A table comparing sensorineural to 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 ....
| Criteria | Sensorineural hearing loss | Conductive hearing loss |
| Anatomical Site | 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:... , cranial nerve VIII, or central processing centers |
Middle ear 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... (ossicular chain), tympanic membrane, or external ear |
| Weber Test Weber test The Weber test is a quick screening test for hearing. It can detect unilateral conductive hearing loss and unilateral sensorineural hearing loss... |
Sound localizes to normal ear Ear The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system.... |
Sound localizes to affected ear (ear with conductive loss) |
| Rinne Test Rinne test The Rinne test is a hearing test. It compares perception of sounds transmitted by air conduction to those transmitted by bone conduction through the mastoid... |
Positive Rinne; Air conduction > Bone conduction (both air and bone conduction are decreased equally, but the difference between them is unchanged). | Negative Rinne; Bone Conduction > Air Conduction (Bone/Air Gap) |
Sensorineural hearing loss may be congenital or acquired.
Congenital
- Lack of development (aplasiaAplasiaAplasia is defined in general as "defective development or congenital absence of an organ or tissue." In the field of hematology, the term refers to "incomplete, retarded, or defective development, or cessation of the usual regenerative process."-Examples:*Acquired pure red cell aplasia*Aplasia...
) of the cochleaCochleaThe 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.... - ChromosomalChromosomeA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
syndromes (rare) - Congenital cholesteatomaCholesteatomaCholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process.-Signs and symptoms:...
- squamous epitheliumSquamous epitheliumIn anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
is normally present on either side of the tympanic membrane. Externally, within the external auditory meatus or ear canalEar canalThe ear canal , is a tube running from the outer ear to the middle ear. The human ear canal extends from the pinna to the eardrum and is about 35 mm in length and 5 to 10 mm in diameter....
and internally within the middle earMiddle earThe 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...
. Within the middle ear the simple epithelium gradually transitions into ciliated pseudostratified epithelium lining the Eustachian tubeEustachian tubeThe Eustachian tube is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi...
now known as the pharyngotympanic tube becoming continuous with the respiratory epitheliumRespiratory epitheliumRespiratory epithelium is a type of epithelium found lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.-...
in the pharynx. The squamous epithelium hyperplasia within the middle ear behaves like an invasive tumour and destroys middle ear structures if not removed. - Delayed familial progressive
Acquired
- InflammatoryInflammationInflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
- Suppurative labyrinthitis
- MeningitisMeningitisMeningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
- MumpsMumpsMumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...
- MeaslesMeaslesMeasles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
- ViralVirusA virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
- SyphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
- OtotoxicOtotoxicityOtotoxicity is damage to the ear , specifically the cochlea or auditory nerve and sometimes the vestibular system, by a toxin. It is commonly medication-induced; ototoxic drugs include antibiotics such as the aminoglycoside gentamicin, loop diuretics such as furosemide, and platinum-based...
drugs- Aminoglycosides (most common cause; e.g., tobramycin)
- Loop diuretics (e.g., furosemideFurosemideFurosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...
) - Antimetabolites (e.g., methotrexateMethotrexateMethotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
) - Salicylates (e.g., aspirinAspirinAspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
)
- Physical traumaPhysical traumaTrauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
- either due to a fractureFractureA fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
of the temporal boneTemporal boneThe temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.The temporal bone supports that part of the face known as the temple.-Parts:The temporal bone consists of four parts:* Squama temporalis...
affecting the cochleaCochleaThe 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....
and middle earMiddle earThe 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...
, or a shearingShearing (physics)Shearing in continuum mechanics refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another. It is induced by a shear stress in the material...
injury affecting cranial nerve VIII.
- Noise-induced - prolonged exposure to loud noises (>90 dBDecibelThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
) causes hearing loss which begins at 4000 Hz (high frequency). The normal hearing range is from 20 Hz to 20,000 Hz. - PresbycusisPresbycusisPresbycusis, 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...
- age-related hearing loss that occurs in the high frequency range (4000 Hz to 8000 Hz).
- Sudden hearing loss
- IdiopathicIdiopathicIdiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
(ISSHL: idiopathic sudden sensoneurinal hearing loss), H91.2 - Vascular ischemiaIschemiaIn medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
of the inner earInner earThe 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:...
or CN 8 - Perilymph fistulaPerilymph fistulaA labyrinthine fistula is an abnormal opening in the bony capsule of the inner ear, resulting in leakage of the perilymph from the semicircular canals into the middle ear . This includes specifically a perilymph fistula , an abnormal connection between the fluid of the inner ear and the air-filled...
, usually due to a rupture of the roundRound windowThe round window is one of the two openings into the inner ear. It is closed off from the middle ear by the round window membrane, which vibrates with opposite phase to vibrations entering the inner ear through the oval window...
or ovalOval windowThe 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...
windows and the leakage of perilymphPerilymphPerilymph is an extracellular fluid located within the cochlea in two of its three compartments: the scala tympani and scala vestibuli. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid...
. The patient will most likely also experience vertigoVertigo (medical)Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...
or imbalanceEquilibrioceptionEquilibrioception or sense of balance is one of the physiological senses. It helps prevent humans and animals from falling over when walking or standing still. Balance is the result of a number of body systems working together: the eyes , ears and the body's sense of where it is in space ideally...
. A history of an event that increased intracranial pressureIntracranial pressureIntracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
or caused trauma is usually present). - Autoimmune - can be due to an IgEIGEIGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
or IgG allergy (e.g. food)
- Idiopathic
- Autoimmune - a prompt injection of steroidSteroidA steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
s into ear is necessary.
- Cerebellopontine angle tumour (junction of the ponsPonsThe pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
and cerebellumCerebellumThe cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
) (the cerebellopontine angle is the exit site of both the facial nerveFacial nerveThe facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(CN7) and the vestibulocochlear nerveVestibulocochlear nerveThe vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
(CN8). Patients with these tumors often have signs and symptoms corresponding to compression of both nerves)- Acoustic neuromaAcoustic neuromaA vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve . The term "vestibular schwannoma" involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are...
(vestibular schwannoma) - this is a schwannomaSchwannomaA schwannoma is a benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves....
(benign neoplasm of Schwann cellSchwann cellSchwann cells or neurolemmocytes are the principal glia of the peripheral nervous system . Glial cells function to support neurons and in the PNS, also include satellite cells, olfactory ensheathing cells, enteric glia and glia that reside at sensory nerve endings, such as the Pacinian corpuscle...
s) - MeningiomaMeningiomaThe word meningioma was first used by Harvey Cushing in 1922 to describe a tumor originating from the meninges, the membranous layers surrounding the CNS ....
- benign tumour of the piaPia materPia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....
and arachnoid materArachnoid materThe arachnoid mater, literally from Latin "spider -like mother", is one of the three meninges, the membranes that cover the brain and spinal cord...
s
- Acoustic neuroma
- Ménière's diseaseMénière's diseaseMénière's disease is a disorder of the inner ear that can affect hearing and balance to a varying degree. It is characterized by episodes of vertigo and tinnitus and progressive hearing loss, usually in one ear. It is named after the French physician Prosper Ménière, who, in an article published...
- causes sensorineural hearing loss in the low frequency range (125 Hz to 1000 Hz). Ménière's disease is characterized by sudden attacks of vertigo, lasting minutes to hours preceded by tinnitusTinnitusTinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
, aural fullness, and fluctuating hearing loss.
Long term exposure to environmental noise
Populations living near airports or freeways are exposed to levels of noise typically in the 65 to 75 dbA range. If lifestyles include significant outdoor or open window conditions, these exposures over time can degrade hearing. The U.S. EPAUnited States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
and various states have set noise standards to protect people from these adverse health risks. The EPA has identified the level of 70 db(A) for 24 hour exposure as the level necessary to protect the public from hearing loss (EPA, 1974).
- Noise-induced hearing loss (NIHL) typically is centered at 4000 Hz.
- The louder the noise is, the shorter the safe amount of exposure is. Normally, the safe amount of exposure is reduced by a factor 2 for every additional 3 dB. For example, the safe daily exposure amount at 85 dB is 8 hours, while the safe exposure at 91 dB(A) is only 2 hours (National Institute for Occupational Safety and Health, 1998). Sometimes, a factor 2 per 5 dB is used.
- Personal audio electronics, such as iPods (iPods often reaching 115 decibels or higher), can produce powerful enough sound to cause significant NIHL, given that lesser intensities of even 70 dB can also cause hearing loss.
Genetic
Hearing loss can be inherited. Both dominant and recessive genes exist which can cause mild to profound impairment. If a family has a dominant gene for deafness, it will persist across generations because it will manifest itself in the offspring even if it is inherited from only one parent. If a family had genetic hearing impairment caused by a recessive gene, it will not always be apparent, as it will have to be passed onto offspring from both parents.Dominant and recessive hearing impairment can be syndromic or nonsyndromic. Recent gene mapping has identified dozens of nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness.
- The most common type of congenital hearing impairment in developed countries is DFNB1, also known as Connexin 26 deafness or GJB2-related deafness.
- The most common dominant syndromic forms of hearing impairment include Stickler syndromeStickler syndromeStickler syndrome is a group of genetic disorders affecting connective tissue, specifically collagen. It was first studied and characterized by Gunnar B. Stickler in 1965. Stickler syndrome is a subtype of collagenopathy, types II and XI...
and Waardenburg syndromeWaardenburg syndromeWaardenburg syndrome Waardenburg syndrome Waardenburg syndrome (also Waardenburg Shah Syndrome, Waardenburg-Klein syndrome, Mende's syndrome II, Van der Hoeve-Halbertsma-Waardenburg syndrome, Ptosis-Epicanthus syndrome, Van der Hoeve-Halbertsma-Gualdi syndrome, Waardenburg type Pierpont,[5] Van...
. - The most common recessive syndromic forms of hearing impairment are Pendred syndromePendred syndromePendred syndrome or Pendred disease is a genetic disorder leading to congenital bilateral sensorineural hearing loss and goitre with occasional hypothyroidism . There is no specific treatment, other than supportive measures for the hearing loss and thyroid hormone supplementation in case of...
, large vestibular aqueduct syndromeLarge vestibular aqueductright|thumb|Interior of right osseous labyrinthLarge vestibular aqueduct, also known as enlarged vestibular aqueduct syndrome, is a syndromic form of hearing loss, caused by enlargement of the vestibular aqueduct, in the inner ear...
and Usher syndromeUsher syndromeUsher syndrome is a relatively rare genetic disorder that is a leading cause of deafblindness and that is associated with a mutation in any one of 10 genes. Other names for Usher syndrome include Hallgren syndrome, Usher-Hallgren syndrome, rp-dysacusis syndrome and dystrophia retinae dysacusis...
. - MT-TL1MT-TL1Mitochondrially encoded tRNA leucine 1 also known as MT-TL1 is a transfer RNA which in humans is encoded by the mitochondrial MT-TL1 gene.-Function:...
mutations cause hearing loss, along with diabetes and other symptomsDiabetes mellitus and deafnessDiabetes mellitus and deafness or maternally inherited diabetes and deafness is a mitochondrial disease associated with the gene "Leu-UUR".-Alternative names:*diabetes and deafness, maternally inherited; MIDD*Ballinger-Wallace syndrome...
.
Disease or illness
- MeaslesMeaslesMeasles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
may result in auditory nerveVestibulocochlear nerveThe vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
damage - MeningitisMeningitisMeningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
may damage the auditory nerve or the cochleaCochleaThe 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.... - Autoimmune diseaseAutoimmune diseaseAutoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...
has only recently been recognized as a potential cause for cochleaCochleaThe 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....
r damage. Although probably rare, it is possible for autoimmune processes to target the cochlea specifically, without symptoms affecting other organs. Wegener's granulomatosisWegener's granulomatosisWegener's granulomatosis , more recently granulomatosis with polyangiitis , is an incurable form of vasculitis that affects the nose, lungs, kidneys and other organs. Due to its end-organ damage, it is life-threatening and requires long-term immunosuppression...
, an autoimmune condition, may precipitate hearing loss. - Autoinflammatory disease, such as Muckle-Wells SyndromeMuckle-Wells syndromeMuckle–Wells syndrome , also known as , is a rare autosomal dominant disease which causes sensorineural deafness, recurrent hives, and can lead to amyloidosis. Individuals with MWS often have episodic fever, chills, and painful joints. As a result, MWS is considered a type of periodic fever syndrome...
, can lead to hearing loss. - MumpsMumpsMumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...
(epidemic parotitis) may result in profound sensorineural hearing loss (90 dBDecibelThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
or more), unilaterally (one ear) or bilaterally (both ears). - PresbycusisPresbycusisPresbycusis, 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...
is deafness due to loss of perception to high tones, mainly in the elderly. It is considered by some to be a degenerative process, although there has never been a proven link to aging. (See impact of environmental noise exposure above.) - Adenoids that do not disappear by adolescenceAdolescenceAdolescence is a transitional stage of physical and mental human development generally occurring between puberty and legal adulthood , but largely characterized as beginning and ending with the teenage stage...
may continue to grow and may obstruct the Eustachian tubeEustachian tubeThe Eustachian tube is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi...
, causing conductive hearing impairment and nasal infections that can spread to the middle earMiddle earThe 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...
. - AIDSAIDSAcquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...
and ARCAIDS-related complexAIDS-related complex, or ARC, was introduced after discovery of the HIV when the medical community became aware of the inherent difficulties associated with treating patients suffering from an advanced case of HIV which gave rise to the term Acquired Immune Deficiency Syndrome...
patients frequently experience auditory system anomalies. - HIVHIVHuman immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
(and subsequent opportunistic infections) may directly affect the cochlea and central auditory system. - Chlamydia may cause hearing loss in newborns to whom the disease has been passed at birth.
- Fetal alcohol syndromeFetal alcohol syndromeFetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...
is reported to cause hearing loss in up to 64% of infants born to alcoholicAlcoholismAlcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
mothers, from the ototoxic effectOtotoxicityOtotoxicity is damage to the ear , specifically the cochlea or auditory nerve and sometimes the vestibular system, by a toxin. It is commonly medication-induced; ototoxic drugs include antibiotics such as the aminoglycoside gentamicin, loop diuretics such as furosemide, and platinum-based...
on the developing fetus, plus malnutrition during pregnancy from the excess alcoholEthanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
intake. - Premature birthPremature birthIn humans preterm birth refers to the birth of a baby of less than 37 weeks gestational age. The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging...
results in sensorineural hearing loss approximately 5% of the time. - SyphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
is commonly transmitted from pregnant women to their fetuses, and about a third of the infected children will eventually become deaf. - OtosclerosisOtosclerosisOtosclerosis is an abnormal growth of bone near the middle ear. It can result in hearing loss.-Clinical description:Otosclerosis can result in conductive and/or sensorineural hearing loss...
is a hardening of the stapes (or stirrup) in the middle ear, and causes conductive hearing lossConductive hearing lossConductive hearing loss occurs when there is a problem conducting sound waves anywhere along the route through the outer ear, tympanic membrane , or middle ear ....
.
Medications
- See also OtotoxicityOtotoxicityOtotoxicity is damage to the ear , specifically the cochlea or auditory nerve and sometimes the vestibular system, by a toxin. It is commonly medication-induced; ototoxic drugs include antibiotics such as the aminoglycoside gentamicin, loop diuretics such as furosemide, and platinum-based...
Some medications cause irreversible damage to the ear, and are limited in their use for this reason. The most important group is the aminoglycoside
Aminoglycoside
An aminoglycoside is a molecule or a portion of a molecule composed of amino-modifiedsugars.Several aminoglycosides function as antibiotics that are effective against certain types of bacteria...
s (main member gentamicin
Gentamicin
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...
).
Various other medications may reversibly affect hearing. This includes some diuretic
Diuretic
A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
s, sildenafil
Sildenafil
Sildenafil citrate, sold as Viagra, Revatio and under various other trade names, is a drug used to treat erectile dysfunction and pulmonary arterial hypertension . It was originally developed by British scientists and then brought to market by the US-based pharmaceutical company Pfizer...
and NSAIDs, and macrolide
Macrolide
The macrolides are a group of drugs whose activity stems from the presence of a macrolide ring, a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered...
antibiotics.
Extremely heavy hydrocodone
Hydrocodone
Hydrocodone or dihydrocodeinone is a semi-synthetic opioid derived from either of two naturally occurring opiates: codeine and thebaine. It is an orally active narcotic analgesic and antitussive...
(Vicodin) abuse is known to cause hearing impairment. There has been speculation radio talk show host Rush Limbaugh
Rush Limbaugh
Rush Hudson Limbaugh III is an American radio talk show host, conservative political commentator, and an opinion leader in American conservatism. He hosts The Rush Limbaugh Show which is aired throughout the U.S. on Premiere Radio Networks and is the highest-rated talk-radio program in the United...
's hearing loss was at least in part caused by his admitted addiction to narcotic pain killers, in particular Vicodin and OxyContin
Oxycodone
Oxycodone is an opioid analgesic medication synthesized from opium-derived thebaine. It was developed in 1916 in Germany, as one of several new semi-synthetic opioids in an attempt to improve on the existing opioids: morphine, diacetylmorphine , and codeine.Oxycodone oral medications are generally...
.
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Physical trauma
- There can be damage either to the ear itself or to the brain centers that process the aural information conveyed by the ears.
- People who sustain head injury are especially vulnerable to hearing loss or tinnitusTinnitusTinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
, either temporary or permanent. - Exposure to very loud noiseNoiseIn common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
(90 dBDecibelThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
or more, such as jet engines at close range) can cause progressive hearing loss. Exposure to a single event of extremely loud noise (such as explosions) can also cause temporary or permanent hearing loss. A typical source of acoustic trauma is a too-loud music concert.
Treatment
Previously, sensorineural hearing loss has been treated with 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, which amplify sounds at preset frequencies to overcome a sensorineural hearing loss in that range; or cochlear implant
Cochlear implant
A cochlear implant is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing...
s, which stimulate the cochlear nerve
Cochlear nerve
The cochlear nerve is a nerve in the head that carries signals from the cochlea of the inner ear to the brain...
directly.
Some research suggests idebenone
Idebenone
Idebenone is an experimental drug, initially developed by Takeda Pharmaceutical Company for the treatment of Alzheimer's disease and other cognitive defects. This has been met with limited success. The Swiss company Santhera Pharmaceuticals has started to investigate it for the treatment of...
alone or combined with vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
may delay the onset of hearing loss or perhaps reverse it. Use of these agents for this purpose is considered experimental now.
Some audiologists and ENTs have reported if severe noise-induced hearing loss (exposures exceeding 140dB) is treated immediately (within 24 hours) with a course of steroids, it can often be almost completely reversed. This, however, is a new field without proven success.
Researchers at the University of Michigan report that a combination of high doses of vitamins A, C, and E, and Magnesium, taken one hour before noise exposure and continued as a once-daily treatment for five days, was very effective at preventing permanent noise-induced hearing loss in animals