Hearing Loss
Hearing Loss: Excerpt from Field Guide to Bedside Diagnosis
Differential Overview
Sensorineural
❑ Presbyacusis
❑ Noise-induced loss
❑ Drugs
❑ Ménière disease
❑ Eighth nerve injury
❑ Acoustic neuroma
❑ Multiple sclerosis
Conductive
❑ Impacted cerumen
❑ Otitis media
❑ Middle ear effusion
❑ Perforation of tympanic membrane
❑ Otosclerosis
❑ Exostoses
❑ Developmental defect
❑ Glomus tumor
Diagnostic Approach
Conductive hearing loss presents with loss of low tones and vowels. Sensorineural hearing loss produces impaired high tone perception, with diminished speech discrimination—especially for female voices—and hearing ringing sounds (tinnitus). Hyperacusis (the sensation that sounds are overly loud to the point of discomfort) is associated with sensorineural cochlear hearing loss. Paracusis (words perceived more clearly in a noisy environment) is associated with conductive middle ear hearing loss.
A reliable qualitative screen for high frequency hearing loss is the ability to hear whispered speech. Stand behind the patient at arm’s length and test one ear at a time. Whisper a combination of 3 letters and numbers (e.g., 4-K-2), and ask the patient to repeat it. The screen is passed when 3/6 are correctly identified. The 256 Hz tuning fork tests 10 to 15 dB, and the 512 Hz 20 to 30 dB. The Rinne test (bone conduction . air conduction) is sensitive to a 20 dB hearing loss. The Weber test is sensitive to 5 dB of hearing loss. A tuning fork is placed in the midline. With conductive loss, it lateralizes to the affected ear, and with sensorineural loss, to the unaffected ear.
Pneumoscopy is performed by first insufflating the ear then releasing. A nonmobile TM may be due to fluid or a mass in the middle ear cavity, or a stiff or sclerotic TM. A hypermobile TM may indicate ossicular chain disruption. A TM that moves only with negative pressure can be due to a retracted TM or a middle ear with a blocked eustacian tube, with resulting negative ear pressure.
Acute hearing loss occurs with infection, traumatic tympanic membrane rupture, or acute vascular event. Unilateral sensorineural loss suggests an inner ear disorder such as Meniere disease or an acoustic neuroma.
Clinical Findings
Presbyacusis Bilateral symmetric hearing loss of gradual onset begins with high frequency loss, manifest as difficulty discriminating voices, particularly high-pitched ones, when there is distracting sound such as conversation in a noisy room, and trouble understanding consonants. There is often tinnitus.
Noise-induced loss Chronic noise levels higher than 90 dB can produce a hearing loss beginning at high frequencies (4000 Hz). Acoustic trauma (e.g., caused by a blast) produces immediate loss resulting from a ruptured tympanic membrane or disarticulation of the ossicles.
Drugs Aminoglycoside antibiotics, furosemide, ethacrynic acid, quinidine, salicylates, and chemotherapeutic agents including cisplatin, 5-fluorouracil, bleomycin, and nitrogen mustard can all cause hearing loss.
Ménière disease Perceived as an asymmetric, fluctuating low-frequency impairment, it is usually associated with tinnitus, fullness in the ear, and episodic vertigo.
Eighth nerve injury Hearing loss may be a sequela of meningitis, mumps, scarlet fever, or skull fracture. Viral cochleitis can cause a sudden hearing loss.
Acoustic neuroma This presents as unilateral progressive hearing loss, vertigo, and notably poor speech discrimination. Look for neurofibromas or cafe-au-lait spots elsewhere.
Multiple sclerosis This can present with sudden hearing loss and/or vertigo. Other manifestations may be present, such as optic neuritis or patchy sensory numbness.
Impacted cerumen Cerumen is apparent on examination of the external auditory canal, and hearing improves immediately after irrigation.
Otitis media The sine qua non is a red and painful tympanic membrane. A middle ear effusion with a thick serous fluid can persist after resolution of the acute infection, producing reduction in hearing for another 4 to 6 weeks.
Middle ear effusion The tympanic membrane is dull but not red, and bubbles or an air-fluid level can be seen through it. The tympanic membrane will not move with exhalation against a closed mouth and nose nor with air insufflation into the ear. Symptoms of viral upper respiratory infection or allergy are usually present.
Perforation of tympanic membrane A hole will be visible in the tympanic membrane. This is sometimes difficult to discern because the usual landmarks are so distorted. Barotrauma, foreign body injury, or blast injury are the usual precipitants.
Otosclerosis Autosomally dominant, this appears in the second or third decade, marked by tinnitus and a reddish color of promontories visible through the tympanic membrane.
Exostoses Bilaterally symmetric bony excrescences appear in the external auditory canal; these are often associated with repetitive cold water exposure (e.g., ocean swimming).
Developmental defect Ossicular malformations are usually associated with atresia of the external auditory canal or deformation of the pinnae.
Glomus tumor The patient presents with conductive hearing loss, spontaneous bleeding from the external auditory canal, and/or paralysis of cranial nerves IX, X, and XI (jugular foramen syndrome). The tumor can be seen as a reddish mass visible through the tympanic membrane, that blanches when positive air pressure is applied.
Pictures
Book Source Details
- Book Title: Field Guide to Bedside Diagnosis
- Author(s): David S. Smith
- Year of Publication: 2007
- Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Field Guide to Bedside Diagnosis
Authors: David S. Smith
Publisher: Lippincott Williams & Wilkins
Copyright: 2007
ISBN: 0-78178-165-5
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