LM210 - Unlocking the Secrets of Middle-Ear Absorption: Measurement and Interpretation Demystified

Abstract: Single frequency (226 Hz and/or 1000 Hz) tympanometry has poor differential diagnostic value in about 30% of middle ear issue cases, particularly in small children. Significant overlap occurs in clinical normative data obscuring differentiation between healthy and pathological ear. Measures of middle ear absorption have become more readily available in commercially available clinical immittance equipment. Middle ear absorbance evaluates function across a wide band of frequencies and therefore helps to clarify those variances. An overview of the measurement and case examples will be presented.

Summary:

Picture this. You are evaluating a cooperative adult whose audiogram indicates significant air-bone gaps. You run a 226 Hz tympanogram, and the tracing looks like a beautiful Type A tympanogram. Is it otosclerosis? Is it a collapsed ear canal? Could it be a cochlear third window pathology? The single frequency tympanogram adds nothing to your picture. Without imaging, how can you give your patient a clear answer? Wideband acoustical absorbance measures can provide you with an answer.

Wideband acoustical absorbance measures, also known as wideband tympanometry, have emerged as a valuable tool in audiology for assessing middle ear function. Unlike traditional tympanometry, which measures the compliance of the middle ear system at a single frequency, wideband absorbance measures provide information across a range of frequencies. This allows for a more comprehensive evaluation of the middle ear and can help in differentiating various pathologies.

 

When faced with a patient presenting with significant air-bone gaps on their audiogram, it is crucial to determine the underlying cause. This is where wideband acoustical absorbance measures come into play. By assessing the absorbance of sound energy across a range of frequencies, these measures can provide insight into the integrity of the middle ear system. Unlike traditional tympanometry, which only provides information about the compliance of the middle ear at a single frequency, wideband absorbance measures offer a more detailed and accurate assessment over the entire audiometric acoustical range.

 

In the case of otosclerosis, wideband absorbance measures can help identify the characteristic patterns associated with this condition. Otosclerosis typically results in a reduction in middle ear absorbance, particularly at low frequencies. However, in cases of a collapsed ear canal, the absorbance pattern would be within normal limits while a cochlear third window pathology would have increased absorbance pattern. Wideband acoustical absorbance measures are a valuable tool in audiology for evaluating middle ear function. They provide a more comprehensive assessment of the middle ear system compared to traditional tympanometry.

 

An overview of middle ear acoustics will be completed, including a summary of the impact on audiometry over the various components of compliance and absorbance. Case studies from adult and pediatric patients will help the learner to apply these concepts into clinical practice.