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CSD 2230 HUMAN COMMUNICATION DISORDERS Topic 5 Hearing Disorders and Hearing Loss Introduction to Sound Types of Hearing Loss Sound System Source Any vibrating object Medium Any gas, liquid or solid Receiver anything designed to detect the vibrations within the medium originating from the source A Common Sound System Illustration of the distribution of molecules surrounding a source in an instant in time Condensation and Rarefaction Bands of condensation and rarefaction emanating from a sound source Propagation of a Disturbance Through a Medium Notice that as time goes on, molecules farther from the source become affected by the disturbance. Important Physical Characteristics of Sound Frequency Rate of pressure change as a function of time Measured as cycles/sec or Hertz The primary determiner of pitch Intensity Magnitude of the pressure change Measured as the decibel (dB) The primary determiner of loudness Frequency and Intensity Sounds a and c share the same frequency and sounds b and c share the same intensity Loudness and Intensity Here are some common sounds and their decibel equivalents The Hearing System Basic schematic diagram of the entire auditory system Putting It All Together…. Types of Hearing Impairment A loss of sensitivity Auditory nervous system pathology Important Terms ü Congenital: Acquired: Adventitious: Time of onset present at birth obtained after birth acquired after birth Important Terms ü Acute: duration Chronic: Sudden: Gradual: time Time Course sudden onset/short long duration rapid onset changes slowly over Important Terms ü Temporary: Permanent: Progressive: Fluctuating: time Time Course limited duration irreversible advancing changes in degree over Important Terms ü Number of Ears Involved Unilateral: Just one Bilateral: Both Hearing Sensitivity Loss § “The ear is not as sensitive as normal in detecting sound” Types: Conductive Sensorineural Mixed Conductive Hearing Loss n “Caused by an abnormal reduction or attenuation of sound as it travels from the outer ear to the cochlea” Sensorineural Hearing Loss n “Caused by a failure in the cochlea to transduce the sound from the middle ear to neural impulses in the VIII Nerve.” Sensorineural Hearing Loss n Implications include: A reduction in the sensitivity of the receptor cells in the cochlea A reduction in the frequency resolving power of the cochlea A reduction in the dynamic range of the system Mixed Hearing Loss n “A loss with both a conductive and sensorineural component.” Types of Hearing Impairment A loss of sensitivity Auditory nervous system pathology Auditory Nervous System Impairment § Causes: Disease Disordered auditory nervous system development Auditory Nervous System Impairment § Kinds: Retrocochlear disorders Central auditory processing disorders Auditory Nervous System Impairment § Auditory Characteristics: Reduced ability to understand speech in a noise background Problems understanding speech with reduced redundancy Problems with localization and lateralization Problems processing normal or altered temporal cues Auditory Pathologies Outer and middle ear disorders Conductive pathologies Cochlear disorders Sensorineural pathologies Central auditory disorders Central auditory pathologies Outer and Middle Ear Disorders Structural defects due to embryologic malformations Structural changes secondary to infection or trauma Outer Ear Disorders Microtia and atresia Microtia “an abnormal smallness of the auricle” n Atresia n “the absence of an opening of the external canal” Outer Ear Disorders Microtia and atresia Impacted cerumen Perforation of the tympanic membrane Outer Ear Disorders Microtia and atresia Impacted cerumen Perforation of the tympanic membrane Other Middle Ear Disorders Otitis Media Most common cause of transient conductive hearing loss in children Inflamation of the middle ear Caused by eustachian tube failure Ways to Classify Otitis Media With or without effusion Fluid type Serous Suppurative Mucoid Ways to Classify Otitis Media With or without effusion Fluid type Duration Acute Chronic Subacute Persistent Recurrent Otitis Media Facts 76-95% of all kids will have one episode of OM by age 6 Prevalence is highest during the first two years of life 50% of all kids with one episode before their first birthday will have 6 or more bouts within two years Most episodes occur in winter and spring Risk factors Cleft palate Down syndrome Native Americans Urban poor Day care Secondhand smoke Middle Ear Disorders Otitis media Otosclerosis Otosclerosis n “a bone disorder that affects the stapes and the bony labyrinth of the inner ear. The disease process is characterized by resorption of bone and new spongy formation around the stapes and oval window” Otosclerosis Facts: Hereditary Women are more likely to develop the disorder Usually bilateral progressive Middle Ear Disorders Otitis media Otosclerosis Cholesteatoma Cholesteatoma n “an epithelial pocket that forms on the tympanic membrane. Once the pocket forms, the normal shedding of epithelium results in growth of the tumor” Middle Ear Disorders Otitis media Otosclerosis Cholesteatoma Other Physical trauma Barotrauma Middle ear tumors Glomus tumor Cochlear Disorders Syndromes and inherited disorders Syndromic disorders Nonsyndromal disorders Syndromes and Inherited Disorders Resulting in Sensorineural Hearing Loss Types of Nonsyndromic Disorders Dominant Dominant progressive Dominant progressive with adult onset Recessive hereditary SNHL X-linked Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Noise Induced Hearing Loss n The degree of SNHL depends on The intensity of the noise The spectral composition of the noise The duration of exposure Individual susceptibility OSHA Damage Risk Criteria Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Infections Congenital Cytomegalovirus HIV Rubella Syphilis Toxoplasmosis Infections Acquired Herpes Zooster Oticus (Chicken Pox) Mumps Syphilis Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Ototoxicity Some antibiotics that are often ototoxic: Amikacin Dihydrostreptomycin Garamycin Gentamicin Kanamycin Neomycin Netilmicin Streptomycin Tobramycin Viomycin Ototoxicity Chemotherapy Carboplatin Cisplatin Drugs that cause reversible hearing loss Quinine Salicylates (aspirin) Loop diuretics Drugs that may be harmful during pregnancy Accutane Dilantin Quinine Thalidomide Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Meniere’s Disease Meniere’s Disease Symptoms Tinnitus Vertigo Unilateral sensorineural hearing loss Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Meniere’s Disease Presbycusis Central Auditory Disorders VIII Nerve tumors Other diseases of the VIII Nerve Neural disorders Brain Stem disorders Cochlear neuritis Diabetes mellitus Infarcts Gliomas Multiple sclerosis Temporal Lobe disorders