* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Hearing Disorders
Survey
Document related concepts
Telecommunications relay service wikipedia , lookup
Olivocochlear system wikipedia , lookup
Sound localization wikipedia , lookup
Auditory processing disorder wikipedia , lookup
Lip reading wikipedia , lookup
Evolution of mammalian auditory ossicles wikipedia , lookup
Hearing loss wikipedia , lookup
Hearing aid wikipedia , lookup
Auditory system wikipedia , lookup
Noise-induced hearing loss wikipedia , lookup
Sensorineural hearing loss wikipedia , lookup
Audiology and hearing health professionals in developed and developing countries wikipedia , lookup
Transcript
Hearing Disorders Properties of Sound • Intensity = loudness – Unit of measure is the decibel (dB) • Frequency = pitch, number of vibrations per second – Unit of measure is Hertz (Hz) • Duration = time – Unit of measure is seconds (s) The Auditory System Peripheral Auditory System (PAS) The Auditory System Central Auditory System (CAS) PAS: Outer Ear • Auricle/Pinna – Localisation PAS: Outer Ear • Ear Canal – Funnels sound • Cerumen PAS: Middle Ear • Tympanic Membrane – Amplifies • Ossicular Chain – Amplifies • Eustachian Tube – Equalises The Eustachian Tube PAS: Inner Ear PAS: Inner Ear • Cochlea – Hearing • Vestibular Apparatus (SemiCircular Canals) – Balance Physiology of the PAS Central Auditory System • Auditory Nerve •30,000 fibres from Cochlea • Brain Stem Nuclei •“cross-over point” • Auditory Cortex (Temporal Lobe) Process of Hearing Audiometry The measurement of hearing Testing the PAS: Air Conduction • “Pure” tones at various frequencies (Hz) and loudness levels (dB) are presented. • Determination of air conduction “threshold.” Air Conduction Testing Testing the PAS: Bone Conduction • “Outer & Middle ears are “bypassed” to test Inner Ear. Various Hz & dB levels are presented. • Determination of bone conduction “threshold.” Bone Conduction Testing Air Conduction & Bone Conduction Hearing Audiogram • Results of audiometric testing are displayed on a graph (dB x Hz). • Smallest numbers are at the top of the graph • Shaded areas represent the general range of normal hearing X = Left Ear Normal range of human hearing is 20 Hz to 20,000 Hz O = Right Ear Hearing Loss X = Left Ear O = Right Ear Another Test of PAS: Otoacoustic Emissions (OAE) OAE Examples Normal Emission Impaired Emission Testing the CAS • Evoked Responses • Auditory Evoked Response • Auditory Brainstem Response (ABR) ABR Examples Testing the CAS: ABR Types of Hearing Loss Portion of Auditory System Affected: Conductive Loss Sensorineural Loss Mixed Loss Ear Affected: Unilateral Bilateral An otoscope Conductive Hearing Loss Results from interference of sound waves that would normally pass through the outer and middle ear. Can be completely corrected (“reversed”) in most cases. Conductive Hearing Loss: Outer Ear Atresia Conductive Hearing Loss: Perforated Ear Drum Conductive Hearing Loss: Impacted Cerumen Conductive Hearing Loss: Otitis Media Myringotomy & Grommets Sensorineural Hearing Loss Results from damage to the cochlea or the auditory nerve and upwards (CAS). The electrical transmission of the sound is affected. Can generally not be fully corrected (irreversible). Sensorineural Hearing Loss: Tumour Sensorineural Hearing Loss: Noise Induced Sensorineural Hearing Loss: Presbycusis Sensorineural Hearing Problem: Tinnitus Mixed Hearing Loss Results from interference of sound waves through outer and/or middle ear AND the electrical transmission of the sound. Hearing Loss: Demographics • 10.5% of NZ population experience hearing loss (approx 450,000 people) • NZ European 10% • Maori 12% • 2 per 1000 newborns (well-baby) • 4 per 100 newborns (NICU) • 4% of population below 45-years of age • 30% of population over 65-years of age • 36% of population over 70-years of age Levels of Hearing Loss Deafness Defined: The permanent and profound loss of hearing in both ears with an auditory threshold of more than 90 decibels. Hard of Hearing: Mild to Severe loss of hearing. Types of Deafness Congenital & Adventitious Language & Deafness Prelingual & Postlingual Risk Factors for Hearing Loss • Early Age Factors: – Genetically inherited (50% of all hearing impairments “run” in families) – Prenatal Disease (rubella, meningitis) – Prematurity (less than 37 weeks gestation, LBW<1500 grams) – Chronic Otitis Media Risk Factors for Hearing Loss • Later Age Factors: – Noise (cochlear damage) – Ageing (Presbycusis) – Drugs (asprin, Lasix) Management of Hearing Loss: Amplification • Typically any hearing loss greater than 25dB is considered (uni- or bi-lateral) Hearing Aid Components • Microphone • Amplifier • Speaker Types of Hearing Aids Body Aid Management of Hearing Loss: Implants • • • • Bone-anchored Hearing Aid Cochlear Implant Brainstem Implant Middle Ear Implant • Involves bypassing or artificially stimulating structures of the auditory system that are not working properly. Bone-Anchored Hearing Aid (BAHA) A BAHA is an auditory implant for people with hearing loss who don't benefit from normal (air conduction) hearing aids. Most common reasons for BAHA are: – Chronic OM - when wearing normal hearing aids makes the infection worse – single sided deafness due to tumours, surgery or trauma – children born with abnormal ears Cochlear Implant • Typically reserved for individuals with severe to profound hearing loss by stimulating the auditory nerve. The implant does not restore normal hearing. Cochlear Implant Middle Ear Implant • External receiver delivers sounds to a transducer implanted in the middle ear that causes the ossicles to vibrate. • Ideal for individuals who cannot tolerate a traditional type of hearing aid that is inserted to the ear canal. Auditory Brainstem Implant The first device specifically designed to bypass the cochlea and the auditory nerve to transmit sound directly to the brainstem.