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Chapter 12: Audiology and Hearing Loss Incidence, Prevalence, and Classification of Hearing Loss Classification of Impairment, Disability, and Handicap  Impairment: a loss of structure or function o Trauma to the eardrum o Damage to the bones of the middle ear o Damage to the sensory cells in the inner ear  Disability: the functional consequence of an impairment o Includes environmental factors that interfere with functioning o Inability to understand speech in the presence of background noise o Difficulty understanding conversations on the phone o Difficulty hearing low-intensity speech sounds  Impairment and disability may lead to participation restriction which is defined as restriction of the ability of a person to participate in life situations  Many individuals who have hearing loss do not have a hearing handicap because their loss does not interfere with their ability to participate in life situations Effects of Hearing Loss  Children o Negative impact on speech and language development o An individual demonstrating loss would have no access to speech sounds in our language without amplification o All degrees of hearing loss, including mild losses, can interfere with speech and language o Children with mild hearing loss typically perform well on basic auditory tasks presented in favorable acoustic environments but when the task becomes challenging the negative effects of hearing loss become more obvious o Children with hearing loss are at great risk for delays in their morphological development o Even though children with unilateral hearing loss have normal hearing in one ear, they are still at risk for academic difficulties due to their loss  Adults o Increased irritability and fatigue due to the extra cognitive effort required to receive needed information o Increased stress o Greater likelihood of becoming isolated due to difficulty participating successfully in conversations o Increased risk of injury related to being less auditorily aware of surroundings o Reduced earning power and less confidence o Reduced self-esteem o Overall reduced psychological health o At risk for psychosocial problems

Deafness, the Deaf Community, and Deaf Culture  Deaf: the term used to describe a person whose hearing loss is in the severe to profound range  Deaf community: a group of persons who share a common means of communication that facilitates group cohesion and identity  American Sign Language: a complex nonvocal language that contains elaborate syntax and semantics. Proficiency in its use is one of the primary methods by which a deaf individual becomes part of the deaf community  Deaf culture: a view of life manifested by the mores, beliefs, artistic expression, understandings, and language that is particular to members of the deaf community What is audiology?  Audiology: professional discipline involving the assessment, remediation, and prevention of disorders of hearing and balance  Related to both assessment and habilitation/ rehabilitation  Although assessment is a critical part of audiology, treatment and management of a client diagnosed with a hearing problem are equally important  Audiologists must be skilled at providing habilitative/ rehabilitative services including counseling, prescribing, and fitting amplification, and various therapeutic services designed to support communication and improve one’s overall quality of life o Amplification: technology such as hearing aids, cochlear implants, and assistive listening devices that improve access to sounds by electronically increasing their intensity Education Requirements and Employment for Audiologists  Most Au.D training programs require 4 years of study beyond the bachelor’s degree  Although the Au.D degree prepares you to understand research and perform clinical research, if you are primarily interested in performing audiology research and/or working at the college level you should pursue a Ph.D in audiology  Once completing your Au.D program, you would be able to seek employment in a wide range of settings Fundamentals of Sound  Several conditions must exist in order to occur and be perceived o The following must be available:  An energy source such as exhalation of air from the lungs  An object capable of vibrating such as the vocal folds of the larynx for the energy source to act on  A medium such as air that is capable of conducting the resulting vibrations  A receptor to receive and interpret the resulting sound  Compression: part of the sound wave where the displaced molecules are in close proximity to each other

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Rarefaction: part of the sound wave where the displaced molecules are far from each other Intensity: a measure of the magnitude of a sound, generally expressed in decibels Frequency: an acoustical term that refers to the number of sound wave cycles that are completed within a specific time period. Subjectively it is perceived as the pitch of a sound

Anatomy and Physiology of the Auditory System  The auditory system can be divided into several general areas o The outer ear o The inner ear o The vestibulocochlear nerve o The auditory brain stem o The auditory cortex of the brain  Peripheral auditory system: part of the auditory system that includes the outer, middle, and inner ears as well as cranial nerve VIII (the auditory nerve)  Central auditory system: part of the auditory system that includes structures beyond the auditory nerve and extending to the auditory cortex The Outer Ear  Outer ear: the section of the ear comprised of the pinna and the external auditory meatus, or ear canal  Pinna: the funnel-shaped outermost part of the ear that collects sound waves and channels them into the ear canal o The most visible structure of the auditory system o Made of cartilage covered with skin o Ridges and depressions provide a natural boost to certain sounds as they enter the ear o Collects and funnels sound into the ear canal and helps the listener to identify where sound originates in space (localization)  External auditory meatus (or canal): the tubular structure that extends from the concha of the pinna to the tympanic membrane  Localization: the process of determining where sound originates in space  Concha: the deep bowl like depression on the pinna  Tympanic membrane (or eardrum): the thin cone-shaped structure composed of three layers of tissue located at the end of the external auditory meatus. It is set into vibration as acoustic energy strikes its surface  Cerumen (or earwax): a substance produced by glands in the ear canal that provides lubrication and protects the ear from invasion of insects and other foreign objects  The ear canal is approximately 1 inch in length in adults and has a slightly “s-shaped” curve as it progresses towards the eardrum

The Middle Ear  Middle Ear: the section of the ear containing the ossicles. It is bounded laterally by the tympanic membrane and medially by the cochlea  Your tympanic membrane is a thin concave-shaped structure that vibrates in response to sound waves that travel down your ear canal o The middle layer of tissue is made of fibrous tissue that provides both the strength and elasticity of the eardrum  A healthy eardrum appears “pearl gray”  Because your eardrum is semitransparent, it is possible to view some of the structures of the middle ear when conducting a visual examination of the eardrum  Middle ear space (or tympanic cavity): the cube-shaped area between the outer and middle ear that contains the ossicles  Eustachian tube: the tube that connects the middle ear cavity with the nasopharynx  Nasopharynx: the space within the skull that is behind the nose and above the roof of the mouth  Malleus: the largest of the ossicles. It is fastened to the eardrum and articulates with the incus, the next bone in the chain  Incus: the middle bone of the ossicular chain in the middle of the ear. It articulates with the malleus at the top and has a projection that is joined to the stapes at the bottom  Stapes: the third and smallest of the ossicles in the middle ear  Ossicles (or ossicular chain): the small bones- the malleus, the incus, and the stapeshoused within the middle ear  Oval window: a small oval membrane located on the lateral wall of the cohlea, behind the stapes footplate

The Inner Ear  Sound waves travel through the air, down the ear canal, and cause the eardrum to vibrate o The vibrations are then carried across the ossicular chain to the footplate of the stapes which makes contact with the oval window, which is the entry point to the inner ear

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Inner ear: the interior section of the ear, which contains the cochlea and vestibular system. It supplies information to the brain regarding balance, spatial orientation, and hearing o Cochlea: the portion of the inner ear that contains the sensory cells of the auditory system. It is composed of two concentric labyrinths. The outer one is composed of bone and the inner one of membrane  Contains special nerve cells designed to respond to auditory stimuli which are referred to as auditory sensory receptor cells  Composed of two complicated networks of passages referred to as labyrinths  Perilymph: the fluid that fills the bony labyrinth of the cochlea and vestibular system  Endolymph: the fluid that fills the membraneous labrynth of the cochlea and vestibular system o Vestibular system: structures of the inner ear that are responsible for supplying information to the brain regarding balance and spatial orientation Organ of Corti: The intricate structure that runs along the center of the membraneous labrynth of the cochlea and contains the auditory sensory receptor cells Basilar membrane: the membrane that forms the floor of the organ of Corti. It is nonuniform in width, thickness, and stiffness and it responds differently to different frequencies of sound (tonotopically). The basilar membrane contains thousands of hair cells, the receptor cells for the auditory system. Located on your basilar membrane are thousands of tiny hair cells o Hair cells: auditory receptor cells located in the organ of Corti that are responsible for encoding auditory information  Stereocilia: small hairlike projections situated on the top of the hair cells in the organ of Corti  Tectorial membrane: the gelatinous tongue-shaped structure that forms the roof of the organ of Corti Vestibulocochlear nerve (or VIIIth cranial nerve): the cranial nerve that runs from the base of the cochlea to the cochlear nucleus of the brains stem. It is composed of the vestibular and cochlear branches Your vestibular system is also made up of bony and membranous sections and contains sensory receptor cells that sense head movement The anatomical connections that exist between the balance and hearing mechanisms help explain why both balance testing and nonmedical intervention of balance disorders are included in the audiologist’s scope of practice

The Central Auditory System  Your central auditory system which consists of nuclei, nerve fibers, and nerve tracts, includes pathways that carry auditory information to your brain and pathways that receive information from your brain Types of Hearing Loss and Auditory Disorders  Conductive System: part of the auditory system made up of the outer and middle ears  The cochlea is the actual sensory organ or hearing, and the auditory branch of the VIIIth nerve is responsible for transmitting the resulting neural signal to the brain stem and eventually to the auditory cortex for processing  Sensorineural system: part of the auditory system made up of the inner ear and cranial nerve VIII Conductive Hearing Loss  If you had a conductive hearing loss, the cause would most likely be the result of a deformation, a malfunction, or an obstruction of the outer or middle ear  Not all disorders of the outer and middle ear result in a loss of hearing but problems in these areas reduce or eliminate the ear’s natural conduction of sound as it travels to the cochlea resulting in the intensity of sound arriving at the inner ear being reduced o This usually prevents low-to moderate-intensity sounds from being heard at all and higher intensity sounds are perceived as much softer than normal  The primary consequence of conductive hearing loss is a loss of loudness or audibility  Conductive hearing loss does not result in a total loss of hearing  Most conductive losses are not permanent o Some resolve without treatment o Most others are medically treatable o Hearing aids may be possible if given medical clearance  Disorders of the Outer Ear o Several conditions of the outer ear can occur due to the malformation of structures during embryonic development o Anotia- pinna absent on one or both sides

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o Microtia: a congenital disorder that results in a small malformed pinna or ear canal o Atresia: a congenital disorder resulting in complete closure of the external auditory meatus o Stenosis is a severe narrowing of the external canal; does not result in significant hearing loss unless debris or earwax becomes trapped in the narrow opening o A much more common cause of conductive hearing loss in the outer ear and one that you may have experiencesd is impacted wax (cerumen) or a foreign object o Overuse of cotton swabs can cause two additional disorders of the outer ear  External otitis, or swimmer’s ear occurs when too much wax has been removed from the ear canal, making the canal more vulnerable to infection by bacteria or fungus  Can be treated by an otolaryngologist or an ear nose and throat physician  Perforation, or hole in the tympanic membrane  The degree of conductive hearing loss resulting from this can be subtle or significant  Can be identified by the ENT physician Disorders of the Middle Ear o Otosclerosis: a disorder characterized by the formation of spongy bone in the region of the stapes footplate, resulting in a progressive conductive hearing loss  Surgery to remove all or part of the stapes footplate followed by insertion of a prosthetic device that acts as an artificial stapes o Ossicular discontinuity- a break somewhere in the ossicular chain  Can be caused by head trauma  Creates a large conductive hearing loss in the affected ear  Surgical repair o Otitis media: inflammation of the middle ear with fluid o Eustachian tube dysfunction: condition in which the Eustachian tube does not adequately equalize middle ear pressure; commonly results in pathology of the middle ear o Otitis media with effusion: inflammation of the middle ear with fluid  Negative middle ear pressure results when the middle ear is not consistently ventilated and oxygen within the cavity is absorbed into the mucous membrane lining, forming a partial vacuum which causes your eardrum to retract into the middle ear cavity, reducing its ability to vibrate freely o Serious otitis media: inflammation of the middle ear with sterile fluid o Purulent (or suppurative) otitis media: pus formation and discharge by the tissue of the middle ear cavity o Treating otitis media is a complex process because no one treatment works best for everyone  Wait and monitor condition

 Use of a decongestant or an antihistamine  Antibiotics such as amoxicillin o ENT (Ear, Nose, and Throat Physician): medical doctor specializing in diagnosis and treatment of diseases of the ear, nose, and throat o Myringotomy: a small surgical incision made in the surface of the tympanic membrane o Pressure equalization (PE) tube (or tympanostomy tube): a small-diameter tube that is surgically placed in the eardrum to provide ventilation of the middle ear space via the external auditory meatus Sensorineural Hearing Loss  Due to absence or malformation of, or damage to the structures of, the inner ear, including the hair cells within the cochlea  May be present at birth or develop over a lifespan  May affect hearing sensitivity for any range of frequencies but higher frequencies are affected in most cases  Can involve both a lack of loudness and a lack of clarity  Certain sounds are inaudible or difficult to hear but sounds that are audible are often perceived as being distorted  Can have a negative impact on speech, language, and cognitive development o Degree of loss o Age of person when loss occurred/ age of onset o The age of the person when the loss was identified o The age of the person when appropriate intervention began  Age of onset is usually described as congenital (present at birth) or acquired (occurring sometime after birth)  Another way is to consider whether the hearing loss occurred prelingually (before speech and language skills developed) or postlingually (after the person had acquired spoken language skills)  Disorders of the Ear o When a hearing loss is due to the absence or malformation of inner ear structures during embryonic development, it is referred to as aplasia or dysplasia  Aplasia or dysplasia: hearing loss due to the absence of the inner ear structures during embryonic development o Usher’s syndrome: a hereditary disorder characterized by sensorineural hearing impairment and progressive blindness o Waardenburg’s syndrome: a hereditary disorder characterized by pigmentary discoloration, particularly in the irises and hair; craniofacial malformation on the nasal area; and severe to profound hearing impairment o Alport’s syndrome: a hereditary disorder characterized by kidney disease and bilateral progressive senseorineural hearing loss o Maternal rubella: german measels contracted during pregnancy that may result in various disorders in the developing fetus

o Meningitis: an inflammation of the meninges, or layers of tissue covering the brain and spinal cord o Ototoxic: refers to drugs and chemical agents that are potentially damaging to the inner wax o Meniere’s disease: a condition resulting from excessive endolymph in the inner ear, involving vertigo, tinnitus, aural fullness, and sensorineural hearing loss o Auditory neuropathy spectrum disorder (ANSD): condition characterized by normal outer hair cell function with abnormal cranial nerve VIII function o Vestibular schwannoma/ acoustic neuroma: refer to a non-malignant growth that develops on the cells near the VIII nerve o Noise induced hearing loss: hearing impairment that results from exposure to high levels of occupational or recreational noise o Temporary threshold shift (TTS): a temporary change in hearing acuity followed by spontaneous recovery that is associated with short-term exposure to highintensity noise o Permanent threshold shift (PTS): A Permanent change in hearing acuity associated with exposure to high-intensity noise o Prebycusis: hearing loss incurred as a result of the aging process Mixed Hearing Loss  Simultaneous presence of conductive and sensorineural hearing loss  In most cases the conductive component can be medically treated, leading to some improvement in overall hearing sensitivity but because the sensorineural component remains the person’s hearing cannot be restored to normal levels (Central) Auditory Processing Disorders  The three types of hearing loss refer to impairment of the peripheral auditory system of the structures of the ear spanning from the pinna to the auditory nerve  The function of the peripheral auditory system is assessed during a comprehensive evaluation

Hearing Loss Through the Lifespan  Early hearing detection and intervention (EDHI) programs: public health initiative designed to facilitate early detection of hearing loss through universal hearing screening, followed by appropriate referral for diagnostic testing and early intervention as necessary  Both newborns and preschoolers are susceptible to hearing loss due to Eustachian tube dysfunction and otitis media which can create a temporary but often difficult to resolve, hearing loss that may negatively affect speech and language development  By middle age some adults with history of early noise exposure begin to experience hearing loss as the effects of noise and aging impact their ability to understand speech  In older individuals age related changes can affect both the cochlear hair cells and auditory nerve fibers resulting in reduced speech understanding Audiological Ass...