Submit Manuscript | http://medcraveonline.com Abbreviations: WNL, within normal limits; AV, alternobaric vertigo; GLAV, ground-level alternobaric vertigo; ETD, Eustachian tube dysfunction; ET, Eustachian tube; ME, middle ear Introduction Tympanometry has been a cornerstone in the evaluation of ME function since its development in the late 1950s and early 1960s. Initially employed for research, it achieved significant clinical application by the 1970s, when researchers established normal values for tympanometry parameters. 1 By the 1980s, comprehensive normative data had been gathered, resulting in the concept of “within normal limits” (WNL). 2 The major goal of this editorial is to critically assess the WNL concept in tympanometry, focusing on its limits in identifying conditions such alternobaric vertigo (AV) and ground- level alternobaric vertigo (GLAV). GLAV is frequently associated with persistent Eustachian tube dysfunction (ETD). 3 It also intends to emphasize the need for a more comprehensive diagnostic approach that incorporates dynamic testing methodologies, full patient histories, and the significance of symmetry in tympanometry data. Backgrounds Tympanometry is a simple test that measures how the tympanic membrane (eardrum) and the ossicles in the ear move in response to changes in air pressure. It checks: ME Pressure: Measure the pressure in the ME compared to the atmospheric pressure. Normal ME pressure ranges from -100 to +50 daPa. Compliance (Admittance): Shows how flexible the tympanic membrane and ossicles in response to air pressure. Normal values range from 0.3 to 1.5 ml. Ear Canal Volume: Measures the volume of air in the ear canal to detect any blockages or holes in the eardrum. Tympanometry Width: Indicates width of the tympanogram peak, used to check for fluid in the ME. 1 These normative ranges for these parameters are established based on population averages, providing a framework for clinicians to determine what is considered “normal”. 3,4 However, these ranges are derived from large population studies and may not adequately capture individual variations in ET and ME function. For example, factors such as age, gender, and ethnicity can influence tympanometry results, leading to variability that is not accounted for by standard normative data. 5,6 Furthermore, static measurements taken during tympanometry do not account for dynamic changes in ME pressure that can occur during activities such as swallowing, yawning, or changes in altitude. These dynamic changes are crucial for diagnosing conditions like AV and GLAV, where pressure equalization is impaired. 7,8 Limitations of the WNL Concept AV, a condition triggered by rapid pressure changes, like during diving or flying, underscores the limits of the WNL concept. 9 AV occurs due to unequal pressure between the MEs, which can cause vertigo even when tympanometry values are WNL. This highlights a critical gap: tympanometry, as a static test, does not capture the dynamic functionality of the Eustachian tube (ET) in real-time changes in ME. 4,7 GLAV, where similar symptoms occur due to pressure changes at ground level, further shows this limitation and is often linked to chronic ETD. 10 Moreover, it is a common bias among otolaryngologists to conclude that a patient presenting with symptoms like dizziness, anxiety, swallowing disorders, and gastrointestinal disorders like abdominal pain, who shows a type A tympanometry result, has no ear problems. This bias can lead to missing conditions like AV, where normal tympanometry results do not rule out significant ETD. 11 The J Otolaryngol ENT Res. 2024;16(2):41‒42. 41 ©2024 Kim. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Reevaluating the notion of “within normal limits” in tympanometry: implications for alternobaric vertigo and more Volume 16 Issue 2 - 2024 Hee-Young Kim Center for Executive and Continuing Professional Education at Harvard T.H. Chan School of Public Health, USA Correspondence: Hee-Young Kim, Harvard T.H. Chan School of Public Health, Center for Executive and Continuing Professional Education, Boston, MA, USA, Tel 617.432.2100, Fax 617.432.2242, Email Received: July 01, 2024 | Published: July 02, 2024 Abstract This editorial explores the notion of “within normal limits” (WNL) in tympanometry, focusing on its limitations in identifying conditions such as alternobaric vertigo (AV) and ground-level alternobaric vertigo (GLAV). Tympanometry is a simple diagnostic instrument that measures middle ear (ME) pressure, compliance, ear canal volume, and the width of tympanogram. While WNL ranges are based on average values from the population, they often do not account for individual differences, leading to possible misdiagnoses. Conditions such as AV, caused by asymmetric ME pressure, can show symptoms even when tympanometry results are within normal ranges. The editorial suggests a more thorough diagnostic approach that includes detailed patient histories, dynamic testing methodologies, and additional hearing and balance tests to improve diagnostic accuracy and patient outcomes. Symmetry in tympanometry data is crucial, and the Valsalva maneuver should be avoided due to potential harm. Future research should aim to improve diagnostic criteria and develop personalized approaches to better understand and manage ME issues. Keywords: tympanometry, within normal limits, alternobaric vertigo, ground-level alternobaric vertigo, eustachian tube dysfunction, middle ear pressure, audiometric assessments Journal of Otolaryngology-ENT Research Editorial Open Access