Signs and Symptoms

Persons with hearing loss frequently report difficulty hearing in background noise. They mistakenly feel others around them are mumbling. They often need the television volume louder than is comfortable for others and ask for things to be repeated. Many experience tinnitus.

Differential Diagnosis

Results of audiometric testing are typically plotted on an audiogram ( Fig. 3.7 ). An audiogram is a graph with frequency (in Hz) plotted on the x axis and intensity (in dB) plotted on the y axis. It is necessary to employ masking (a static type of noise) in certain situations to prevent the nontest ear from detecting the test signal.

Results of the audiogram and tympanogram ( Fig. 3.8 ) may suggest various forms of otologic disease. Red flags should prompt referral to an otolaryngologist (discussed below). Otologic disease may be categorized as conductive hearing loss, sensorineural loss (SNHL), or mixed hearing loss. In a conductive loss, there is an air–bone gap on the audiogram, with better bone conduction thresholds, with appropriate masking. The loss may be due to dysfunction involving the external canal, tympanic membrane, or ossicular chain or to middle ear fluid. In a sensorineural loss, bone conduction thresholds typically equal air conduction, and the loss may be due to dysfunction at the level of the cochlea, CN VIII, or central pathways. A poor word-recognition score, especially out of proportion to pure tone thresholds, suggests possible retrocochlear pathology, such as an acoustic tumor.

Patterns of SNHL may be suggestive of certain etiologies, taken together with clinical history and exam. For example, acoustic trauma (noise-induced loss) often results in a loss centered around 4 kHz with recovery at higher frequency (i.e., a 4-kHz notch); presbycusis often involves symmetric downsloping loss, worse at higher frequency; a fluctuating low-frequency loss is often seen with Ménière′s disease.

The Jerger system is commonly used to classify tympanometric results:

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  Type A: Normal

  
  
  
  
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    Pressure peak +100 to −100 daPa

    
    
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    Immittance 0.3 to 1.7 mL

  
  
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  Type As: Shallow

  
  
  
  
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    Pressure peak +100 to −100 daPa

    
    
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    Immittance < 0.3 mL

  
  
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  Type Ad: Deep

  
  
  
  
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    Pressure peak +100 to −100 daPa

    
    
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    Immittance > 1.7 mL

  
  
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  Type C: Negative pressure

  
  
  
  
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    Pressure peak ≤ 100 daPa

    
    
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    Immittance normal or shallow

  
  
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  Type B: Flat

  
  
  
  
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    No pressure peak or immittance

    
    
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    Small ear canal volume suggests ear canal occlusion.

    
    
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    Normal volume suggests otitis media.

    
    
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    Large ear canal volume suggests patent pressure equalization tube or perforated eardrum.

Tuning Fork Tests

The goal of these tests, including the Weber test ( Fig. 3.9 ), is to differentiate between conductive and SNHL. The tuning forks vibrate at a fixed frequency between 256 and 1024 Hz. To test bone conduction, the fork is placed firmly on the skull bone. Typically, a 512-Hz tuning fork is used.

Weber Test

The Weber test will lateralize to the ear with worse conductive loss if sensory hearing is equal in both ears ( Fig. 3.9 ). Alternatively, the Weber test will lateralize to the ear with better sensory hearing if there is no conductive hearing loss in either ear.

Rinne Test

The Rinne test ( Fig. 3.10 ) compares the level of air conduction and bone conduction in the same ear. In a normal ear, air conduction is greater. It usually takes about a 30-dB conductive loss to flip the tuning fork response to bone conduction greater than air.