Contralateral Occlusion Test: The effect of external ear canal occlusion on hearing thresholds

Tympanic membrane perforations: the importance of etiology, size and location

PURPOSE

The ability to predict the degree of a conductive hearing loss caused by a tympanic membrane perforation is important for every otologist, as it may require additional diagnostic tests and prevent unexpected intraoperative findings. The aim of this study was to correlate the various characteristics of a perforation (etiology, size, location, involvement of the manubrium or umbo) with the degree and frequency predominance of the consequent hearing loss.

METHODS

A transversal study in a tertiary hospital center was conducted between July 2019 and December 2020. Fifty-eight patients with 65 tympanic perforations underwent a comprehensive medical and audiological evaluation, which included an otoendoscopy. An image processing software (ImageJ®) was used to measure the perforated area. The qualitative variables were etiology, affected quadrants, presence of myringosclerosis and involvement of umbo or manubrium of the malleus. The air-bone gap was measured at 250, 500, 1000, 2000 and 4000 Hz. Primary outcomes (mean air-bone gap and pure-tone average) were evaluated to find clinical factors associated with worse hearing.

RESULTS

Data collected from 50 ears was included. Perforation size showed a positive statistically significant correlation with the air-bone gap (r = .508; p < .001) and pure-tone average (r = .375; p < .001). Higher air-bone gaps were found in perforations involving the posterior quadrants and the manubrium (p < .001 and p = .031, respectively). Inflammatory causes showed higher bone and air conduction pure-tone averages (p = .031 and p = .084, respectively) compared to traumatic or iatrogenic. An "inverted V" pattern of the air-bone gap, with the 2 kHz frequency being the least affected, was a consistent finding. However, it was not due to the Carhart's notch in bone conduction.

CONCLUSION

The conductive hearing loss resulting from a tympanic membrane perforation is etiology, size and location-dependent, with higher losses occurring for inflammatory backgrounds, large perforations and when the posterior quadrants or the manubrium are involved. If the "inverted V" is absent, additional middle ear pathology should be investigated.

Contralateral occlusion test: The effect of external ear canal occlusion on predicting conductive hearing loss

INTRODUCTION AND OBJECTIVES

The contralateral occlusion test (COT) has the potential to allow the quantitative evaluation of unilateral conductive hearing loss. The purpose of this study was to determine the accuracy of the test in predicting the degree of hearing loss.

MATERIALS AND METHODS

Fifty-three subjects with unilateral conductive hearing loss were recruited from an otolaryngology department of a tertiary hospital. The COT was performed using 128, 256, 512, 1024 and 2048Hz tuning forks with the non-affected ear canal totally occluded to determine lateralization. Pure-tone audiometry was performed to establish the presence and degree of the air-bone gap (ABG) and the pure-tone average (PTA). The tuning fork responses were correlated with the ABG and the PTA to determine their accuracy.

RESULTS

The COT showed a better association between hearing loss and the lateralization response using the 512Hz tuning fork (p=0.001). The sensitivity of the 512Hz fork in detecting a PTA of at least 35.6dB was 94.6% and the specificity was 75.0% for a positive predictive value of 89.7% and a negative predictive value of 85.7%, assuming a pretest prevalence of 69.8%.

CONCLUSIONS

The overall accuracy of the COT in predicting the degree of unilateral conductive hearing loss was significant. The COT had significant power in one direction: if lateralization to the affected ear occurred, it was almost certain evidence of a moderate or severe conductive hearing loss.

Contralateral Occlusion Test (COT): the effect of external ear canal occlusion with aging

PURPOSE

This study aimed to evaluate the effects of complete external ear canal occlusion on hearing thresholds with aging. The goal was to decide which tuning fork is more appropriate to use for the contralateral occlusion test (COT), in individuals of different ages.

METHODS

Forty-two normal hearing subjects between 21 and 67 years were divided into three age groups (20-30 years, 40-50 years, and 60-70 years). Participants underwent sound field audiometry tests with warble tones, with and without ear canal occlusion. Each ear was tested with the standard frequencies (250, 500, 1000, and 2000 Hz). The contralateral ear was suppressed by masking.

RESULTS

Hearing thresholds showed an increase as the frequency increased from 20.85 dB (250 Hz, 20-30 years group) to 48 dB (2000 Hz, 60-70 years group). The threshold differences between occlusion and no occlusion conditions were statistically significant and increased ranging from 11.1 dB (250 Hz, 20-30 years group) to 32 dB (2000 Hz, 20-30 years group). We found statistically significant differences for the three age groups and for all evaluations except to 500 Hz difference and average difference. The mean hearing loss produced by occlusion at 500 Hz was approximately 19 dB. We found no statistically significant differences between right and left ears and gender for all measurements.

CONCLUSION

We conclude that the use of the 512 Hz tuning fork is the most suitable for COT, and its use may allow clinicians to distinguish mild from moderate unilateral conductive hearing loss.

Pars tensa and tympanicomalleal joint: proposal for a new anatomic classification

PURPOSE

The tympanic membrane (TM) belongs to the ear. Despite its place in the ear anatomy, can we give it also a different anatomic classification? The main objective is to clarify the nature of TM, tympanic bone and malleus to propose a new anatomic classification.

METHODS

This cadaveric study was performed in two human heads and six fresh temporal bones. A study of the temporomandibular joint, external acoustic meatus (EAM), TM and middle ear structures was conducted. A medical literature review englobing anatomy, embryology, histology and phylogeny of the ear was performed and the results were compared with the results of the dissection.

RESULTS

The external ear is constituted by the auricle and the EAM. This last segment is made by a cartilaginous and an osseous portion. The osseous portion of the EAM is constituted mainly by tympanic bone. The external ear is separated from the middle ear by the TM. Inside the middle ear, there are three ossicles: malleus, incus and stapes, which allow the conduction of sound to the cochlea. Based on the anatomic dissection and medical literature review of the tympanic bone, malleus and TM, we propose that these structures are interconnected like a joint, and named it "Tympanicomalleal joint".

CONCLUSIONS

It seems that the TM can be part of a joint that evolved to improve sound transmission and middle ear protection. Thinking TM has part of a joint may help in the development of more efficient reconstructive surgical techniques.