Hearing loss Notes


Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Hearing loss essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Hearing loss:

Conductive hearing loss

NOTES NOTES HEARING LOSS GENERALLY, WHAT IS IT? PATHOLOGY & CAUSES ▪ Decrease in ability to perceive sound ▪ Variable etiology ▫ External, middle, inner ear, associated neurological input/processing structures SIGNS & SYMPTOMS ▪ Hearing loss ▪ Balance issues, headache, tinnitus DIAGNOSIS OTHER DIAGNOSTICS ▪ Bedside (otoscopy to Rinne) and formalized (audiogram) testing Otoscopy Whisper test ▪ Examiner speaks in whispered voice 0.61m/2ft away → individual covers far ear with hand → examiner whispers word/ phrase → individual repeats word/phrase Finger rub ▪ Examiner speaks closer to pinna → individual indicates if sound heard Weber ▪ Distinguishes between conductive, sensorineural hearing loss ▪ Examiner places vibrating tuning fork (128Hz) at apex of head → individual indicates loudest side ▫ One ear preferred/louder indicative of possible hearing loss Rinne ▪ Compares air, bone conduction of sound ▪ Examiner places vibrating tuning fork (512Hz) at mastoid process → individual indicates when vibration heard → examiner moves vibrating tuning fork outside of pinna → individual indicates if vibration heart ▫ Bone conduction (mastoid placement of tuning fork) > air conduction (i.e. individual cannot hear vibration after first step complete) indicative of possible hearing loss Audiogram ▪ Pure tones of varying frequencies (Hz) at varying volume of sound ▪ Plot individual’s 50% correct response rate (dependent on volume) for each frequency TREATMENT ▪ Specific to underlying etiology; some etiologies irreversible 622 OSMOSIS.ORG
Chapter 80 Hearing Loss CONDUCTIVE HEARING LOSS osms.it/conductive-hearing-loss PATHOLOGY & CAUSES ▪ Disability of sound waves ▫ Unable to be amplified, transmitted by external/middle ear CAUSES Bony outgrowth ▪ Exostoses: form at suture lines of external auditory canal bony suture lines; associated with repeated cold water exposure (e.g. swimmers) ▪ Osteomas: form at tympanosquamous suture line Cerumen impaction ▪ ↑ Incidence in elderly Congenital ▪ Microtia: malformation/absence of auricle; 1st, 2nd branchial arch derivative; mildmoderate conductive hearing loss ▪ External auditory canal atresia: associated with craniofacial diseases (e.g. Treacher Collins syndrome, Robin sequence, Crouzon syndrome) ▪ Commonly of ossicular chain (most commonly malformation of stapes) → inability to reverberate → ↓ sound wave transmittance to oval window Eustachian tube dysfunction ▪ Results in abnormal pressure/reflux/ clearance of middle ear contents ▪ Shorter eustachian tubes in children → ↑ reflux of nasopharynx contents → otitis media ▫ Higher incidence in children with abnormal craniofacial anatomy (e.g. Down syndrome, Treacher Collins syndrome) Otitis externa ▪ AKA swimmer’s ear ▪ Commonly bacterial ▫ Pseudomonas aeruginosa (most common pathogen) ▪ Chronic/repeated infections → polyps (can occlude external auditory canal) Otitis media ▪ Infection → effusion → poor transmittance of sound wave in middle ear → hearing loss ▪ Highest incidence ▫ 6–18 months of age ▪ Microbiology: Staphylococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis ▪ Risk factors: daycare, bottle feeding ▪ Complications: mastoiditis, cholesteatoma, permanent hearing loss → deafness OSMOSIS.ORG 623
Otosclerosis ▪ Bony overgrowth of stapes to oval window → inability to vibrate → inability to conduct sound waves; can be autosomal dominant with variable penetrance Trauma ▪ Complete external auditory canal occlusion Tumors of middle ear ▪ Cholesteatomas (most common overall) ▫ Desquamated, stratified, squamous epithelium in middle ear space ▫ Accumulation → erosion of middle ear contents (ossicular chain) → surrounding structures: external auditory canal (EAC), mastoid bone ▪ Squamous cell carcinoma (most common malignant tumor) Tympanic membrane perforation ▪ Common; due to trauma/barotrauma to ear/ face SIGNS & SYMPTOMS ▪ Decreased perception of sound ▫ Especially poor perception of lowfrequency sound ▫ Overcome by volume of stimulus DIAGNOSIS OTHER DIAGNOSTICS ▪ History, associated symptoms ▪ Otoscopy ▪ Special testing ▫ Weber (localization of vibration to affected ear) ▫ Rinne (abnormal; bone conduction > air conduction) ▪ Audiogram ▫ Universal/low-frequency deficit in pure tone discrimination 624 OSMOSIS.ORG TREATMENT ▪ Specific to underlying etiology MEDICATIONS ▪ External ear ▫ Mild: topical acidifying agent, glucocorticoid ▫ Moderate/severe: topical/oral antibiotics ▪ Middle ear ▫ Pain control (e.g. ibuprofen, acetaminophen), antibiotics SURGERY ▪ External ear ▫ If repeat infections/↑ size ▪ Middle ear ▫ Tissue graft ▫ Surgical removal OTHER INTERVENTIONS ▪ External ear ▫ Cerumenolytics/irrigation/manual removal ▫ Repeat infections/↑ size: EAC occlusion ▪ Middle ear ▫ Hearing aids
Chapter 80 Hearing Loss OSMOSIS.ORG 625
SENSORINEURAL HEARING LOSS osms.it/sensorineural-hearing-loss PATHOLOGY & CAUSES ▪ Disability of inner ear (cochlea/CN VIII) to transduce sound waves → viable neurologic input → brain CAUSES Central nervous system (CNS) ▪ Acoustic neuroma (CN VIII; AKA vestibular neuroma) ▫ ↑ size → compress cerebellum → ataxia ▪ Meningitis ▫ Infection (via cerebrospinal fluid) → cochlea → cochleitis → direct damage to inner hair cells ▪ Meningioma ▪ Acoustic nerve neuritis ▫ Multiple sclerosis, syphilis Congenital ▪ Spontaneous/genetic ▪ Acquired ▫ Toxoplasmosis, other (syphilis, varicella-zoster, parvovirus B19), rubella, cytomegalovirus (CMV), herpes (TORCH) infections Drug-induced ▪ Aminoglycoside antibiotics (most common); cisplatin ▪ Aspirin (high-dose 6–8g/day), quinidine, loop diuretics (e.g. furosemide, ethacrynic acid) → reversible hearing loss, tinnitus Inner ear infection ▪ Labyrinthitis (inflammation, spinning, ringing) Menière’s disease ▪ Rare 626 OSMOSIS.ORG ▪ Unilateral, episodic loss concurrent with tinnitus, vertigo ▫ Pathogenesis: unknown; possible infection, autoimmune, vascular constriction, congenital malformation → endolymphatic hydrops (e.g. overproduction of endolymph, distension of endolymphatic space) Noise-induced ▪ Cause: chronic exposure to loud (> 85dB) auditory stimuli ▪ Pathogenesis: overstimulation of hair cells in organ of Corti → nitric oxide, free radical release → damage, death of hair cells ▪ ↓ Mg2+ → ↓ Ca2+ intracellular concentration → ↑ cell damage, death Presbycusis ▪ Most common ▪ Gradual, symmetric hearing loss in elderly ▪ More significant loss with higher frequencies ▪ Pathogenesis: degeneration of hair cells at base of cochlea Trauma ▪ Skull fracture → injury to CN VIII/cochlea SIGNS & SYMPTOMS ▪ Decreased perception of sound (esp. highpitched sounds, speech discrimination) DIAGNOSIS DIAGNOSTIC IMAGING MRI ▪ Identifies causes such as acoustic neuroma, perilymphatic fistula
Chapter 80 Hearing Loss OTHER DIAGNOSTICS ▪ History, associated symptoms ▪ Otoscopy ▫ Rules out causes of conductive hearing loss ▪ Special testing ▫ Weber: lateralization of sound to unaffected ear ▫ Rinne: air, bone conduction (AC > BC) ▪ Audiogram ▫ Identifies deficit in high-pitched pure tone discrimination TREATMENT ▪ Antibiotics ▫ Meninges SURGERY ▪ Surgical resection ▫ Acoustic nerve OTHER INTERVENTIONS ▪ Hearing aids ▫ Hair cells of organ of Corti ▪ Dietary changes (↓ Na+) ▫ Endolymph of labyrinthine systems ▪ Radiotherapy ▫ Acoustic nerve ▪ Specific to underlying etiology MEDICATIONS ▪ Antiemetics, vestibular suppressants (e.g. benzodiazepines), diuretics ▫ Endolymph of labyrinthine systems OSMOSIS.ORG 627

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Hearing loss essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Hearing loss by visiting the associated Learn Page.