Review of Audiology Chapter 4 PDF

1. Introduction to Hearing and Hearing Loss Hearing: reception of sound by ear, its analysis, and its transmission to brain Hearing Impairment: Defined as any loss or abnormality in the structures or functions of the ear and auditory pathways. 2. Range and Levels of Hearing Loss (10-2...

1. Introduction to Hearing and Hearing Loss Hearing: reception of sound by ear, its analysis, and its transmission to brain Hearing Impairment: Defined as any loss or abnormality in the structures or functions of the ear and auditory pathways. 2. Range and Levels of Hearing Loss (10-25 dB) Normal (26-40 dB) Mild Loss (41-55 dB) Moderate (56-70 dB) Moderate Severe (71-90 dB) Severe ( Greater than 90 dB) Profound Sound Levels: Safe Range (30-75 dB): 30 dB: Equivalent to a whisper, posing no risk of hearing damage. 40 dB: Noise level typical of a refrigerator. 60 dB: Normal conversation, which is comfortable and safe for continuous exposure. 75 dB: Equivalent to a dishwasher, slightly louder but still within safe limits. Risk Range (85-165 dB): 85-95 dB: Sounds like heavy city traffic or a school cafeteria fall within this range. Prolonged exposure can begin to cause hearing damage. 100-120 dB: Sounds from motorcycles, snowmobiles, or rock concerts. At this level, even brief exposure can be harmful. 140-165 dB: Fireworks or firearms produce these extreme sound levels. Immediate exposure can lead to permanent hearing damage. Age of Hearing Impairment: Prelingual: loss of hearing before speech and language developed Postlingual: loss of hearing after spontaneous speech and language has developed. 3. Types of Hearing Loss Conductive Hearing Loss: Originates from problems in the outer or middle ear, blocking or reducing sound transmission. Common issues include obstructions (earwax), infections (otitis externa or otitis media), or structural malformations. Sensorineural Hearing Loss (SNHL): Caused by damage to the inner ear or auditory nerve. Often permanent, as it usually involves damage to the hair cells in the cochlea or the auditory nerve. Mixed Hearing Loss: A combination of conductive and sensorineural hearing issues, affecting multiple parts of the ear and auditory pathways. 4. Causes of Hearing Impairment Hearing impairment can be classified into different types based on origin: Hereditary vs. Non-hereditary Congenital vs. Acquired Physiological and Psychological. Prenatal, Perinatal, and Postnatal 5. Risk Factors: Aging Loud Noise Exposure Infections and Illnesses Genetics Injury 6. Causes of Hearing Loss: Detailed Classification  Conductive Hearing Loss: Congenital Conductive Causes: Microtia: Deformities in the external ear (pinna) ranging in severity. External Ear Canal Atresia/Stenosis: Either complete absence or narrowing of the external ear canal, affecting sound transmission, usually unilateral and with other Craniofacial Abnormalities: Syndromes such as Treacher-Collins, Robin sequence, and Crouzon syndrome. Tympanic Membrane Issues: Congenital cholesteatoma (2-3%) can grow a white mass behind the eardrum, causing obstructions. Ossicular Malformations: The ossicular chain (malleus, incus, stapes) may be malformed, impeding sound transmission ( won’t vibrate properly causing improper amplification of sound) ▪ Stapes atresia is most common ▪ Osteogenesis imperfecta: brittle bone disease, 50% of individuals with OI have hearing loss. Acquired Conductive Causes: Otitis Externa: Inflammation/infection of the external auditory canal/pinna or both, often due to bacterial or fungal infections. Otitis Media with Effusion: Thick fluid buildup in the middle ear, which affects eardrum mobility and sound conduction. Temporary hearing loss of 25dB until fluid disappears. Cholesteatoma: A benign growth that can compress structures in the middle ear, hearing loss occurs due to increased size of growth (made of keratin and cells) if left untreated. Otosclerosis: Abnormal bone growth near the stapes in the middle ear, which restricts movement and sound transmission. Foreign Body or Earwax Blockage: These obstructions can impede sound from reaching the eardrum. Trauma: due to change of pressure, loud noises, temporal bone fractions, etc. Sensorineural Hearing Loss: Congenital SensorineuralCauses: Prenatal Infections:  Cytomegalovirus (CMV): Common virus and the leading cause of sensorineural hearing loss with delayed or progressive onset. Toxoplasmosis: mimics herpes, cytomegalovirus, and rubella o Syphilis: bacterial infection passed by pregnant moms, become infected through the placenta. Can be prevented. Hearing loss by age 2. Genetic Factors: Autosomal Recessive (80% of genetic causes) and Autosomal Dominant (20% of genetic causes): Inherited traits may lead to hearing loss with or without associated syndromes. Autosomal dominant: one parent affected other is not. Autosomal recessive: both parents are carriers of disease. Both can occur as nonsyndromic: hearing loss without symptoms or syndromic: hearing loss with abnormalities is other parts of body. Anatomic Abnormalities: Michel Aplasia (Complete Labyrinth Aplasia): Complete absence of the inner ear. Mondini Dysplasia: Partial malformation of the cochlea and other inner ear structures. Scheibe (Saccule) and Alexander (Membranous Labyrinth) Anomalies: Degeneration and malformations in inner ear components. Environmental Prenatal Factors: Exposure to ototoxic drugs, prematurity, hypoxia, or excessive incubator noise can lead to congenital sensorineural impairment. Acquired Sensorineural Causes: Infections: bacterial meningitis Trauma to temporal bone Noise exposure, tumors, radiation, neurodegenerative disorders Renal tubular acidosis with deafness: kidney problems and hearing loss Hyperbilirubinemia: Bilirubin is toxic to central auditory pathways and cochlear nuclei. 7. History and Risk Assessment for Hearing Loss  Neonate Risk Factors: Family history of hearing loss, low birth weight, low APGARScore, and prolonged mechanical ventilation are significant indicators. Hyperbilirubinemia (high bilirubin levels) can be toxic to auditory pathways if untreated. Post-28 Days Risk Factors: Parental Concern, Persistent otitis media for over three months, head trauma, bacterial meningitis, and specific syndromes linked to hearing loss all contribute to the risk profile. CONDUCTIVE HEARING LOSS SENSORINEURAL HEARING LOSS MIXED HEARING LOSS