The tympanic membrane (TM), commonly referred to as the eardrum, plays a crucial role in the auditory system by facilitating sound transmission from the external environment to the middle ear. When a perforation occurs, it compromises this function by reducing the available surface area for sound conduction and allowing direct entry of sound waves into the middle ear ^{1, 2}. Research has shown that TM perforation can result in conductive hearing loss (CHL), ranging from negligible to as much as 50 decibels (dB) ³.

Several factors influence the degree of hearing loss associated with TM perforations. Among these, the size and location of the perforation are of particular interest. Multiple studies indicate a direct correlation between the size of TM perforation and the severity of hearing loss: the larger the perforation, the greater the loss ^{4, 5}. Additionally, hearing loss varies inversely with the volume of air within the middle-ear and mastoid cavity, meaning that individuals with smaller middle ear cavities tend to experience more severe CHL for the same perforation size ^{6, 7}.

The impact of the location of TM perforation on hearing loss, however, remains a topic of debate. Some researchers suggest that the perforation site does not significantly influence hearing loss ^{3, 4}, while others propose that perforations in the postero-inferior quadrant, near the round window, result in greater hearing impairment ^{2, 8}. The theoretical basis for this observation is that posteriorly located perforations may allow sound energy to bypass the ossicular chain, leading to an inefficient transmission of sound and a more pronounced hearing deficit.

Moreover, the chronicity of TM perforations also contributes to variations in hearing loss severity. Long-standing perforations, especially those associated with recurrent infections, may lead to sclerotic changes in the mastoid air cells, further compounding the hearing impairment ^{9, 10}. Although acute perforations resulting from trauma or acute otitis media often heal spontaneously, persistent perforations may necessitate surgical intervention, such as tympanoplasty, to restore auditory function ¹¹.

Given the variability in findings regarding the effect of perforation site and size on hearing loss, this study aims to determine the correlation between the size and site of tympanic membrane perforation and hearing loss among adult patients with tympanic membrane perforation in  Port Harcourt, Nigeria

Materials and Methods

Study Area: This study was conducted at the University of Port Harcourt Teaching Hospital (UPTH), Rivers State, Nigeria, a reference hospital with a bed capacity of 800. The ENT clinic operates four days a week, serving approximately 4,200 patients annually.

Study Design: A hospital-based cross-sectional study was employed, focusing on patients with unilateral tympanic membrane (TM) perforation attending the ENT clinic.

Study Population: The study included adult patients ≥18 years with unilateral TM perforation, while the contralateral non-perforated ear served as the control.

Inclusion Criteria

• Adult patients ≥18 years.
• Patients with unilateral or multiple TM perforations who gave consent.

Exclusion Criteria

• Bilateral TM perforation.
• Previous ear surgery.
• History of ototoxicity, diabetes mellitus, sickle cell anemia, or HIV infections.
• Severe external auditory canal stenosis.
• All patient > 60 years

Study Duration: The study spanned from August 1, 2018, to July 31, 2019.

Scope of Study: The study assessed the degree, pattern, and type of hearing loss associated with TM perforations, alongside middle ear volume. Assessment methods included otoscopy, video otoscopy, pure tone audiometry, and tympanometry.

Sample Size Determination: Using Cochran’s formula, the minimum sample size was calculated to be 61, with a 10% allowance for non-response, resulting in a final sample size of 70 patients (140 ears).

Materials:

• Otoscope: Heine mini 3000 otoscope, Germany.
• Audiometer: Madsen Itera model, Denmark.
• Tympanometer: Madsen Zodiac 901, Denmark.
• Pure Tone Audiometry Equipment: Soundproof booth, Kahntact BB 100 model, USA.
• Video Otoscopy: MD Scope, Apple Biomedical, USA.
• Data Analysis Software: Image J version 1.51p (Wayne Rasband, NIH, USA).

Sampling Method: A cluster sampling technique was employed, selecting two clinic days (Monday to Thursday) randomly. All patients with unilateral TM perforation on those days were included in the study.

Data Collection: A structured, interviewer-administered questionnaire was used to gather demographic and clinical data from each participant. The questionnaire included questions on the patient's age, gender, and medical history, with particular focus on ear-related symptoms, such as pain, drainage, and hearing loss. It also addressed potential causes of tympanic membrane perforation, such as trauma, ear infections, or ototoxicity due to medication. Further details were collected regarding the patients’ medical history, including conditions like diabetes, sickle cell anemia, and prior ear surgeries. Information on any history of ototoxicity or retroviral infections was also documented. Following the interview, patients underwent pure tone audiometry (PTA), which was performed using a calibrated Madsen Itera audiometer inside a soundproof booth. The PTA evaluated both air and bone conduction thresholds at frequencies of 250, 500, 1000, 2000, 4000, and 8000 Hz to assess the type and degree of hearing loss ^{1, 12}. Air conduction testing was done using supra-aural earphones, while bone conduction testing was performed using a bone oscillator placed over the mastoid bone ¹². Air conduction masking was performed when the air conduction threshold in the perforated ear was 40 dB greater than the bone conduction threshold in the normal contralateral ear, using the plateau seeking method. Bone conduction masking was done for all patients at all frequencies. Pure-tone averages were calculated for air and bone conduction at 500, 1000, 2000, and 4000 Hz ^{12, 13}. An air-bone gap greater than 10 dB in these frequencies was considered significant for diagnosing conductive hearing loss ¹². Sensorineural hearing loss was defined as air and bone conduction averages within 10 dB, with thresholds above 25 dB HL ¹². Mixed hearing loss was defined as a gap greater than 10 dB between air and bone conduction averages, with thresholds above 25 dB HL at any frequency ¹². Results was used to grade hearing threshold into mild, moderate, severe and profound hearing according to WHO ¹⁴. These assessments provided critical data for analyzing the relationship between tympanic membrane perforations and hearing impairment in the study population. Video otoscopy was performed using a probe with an appropriate speculum, and the tympanic membrane was fully visualized. A digital image of the perforation was captured, and its size was analyzed with Image J software by measuring the perforated area in relation to the tympanic annulus¹. The site of the perforation was recorded, referencing an imaginary line through the manubrium of the tympanic membrane (TM). Sites included anterio-superior, posterio-superior, anterio-inferior, posterior-inferior, subtotal, and central perforations¹.

These assessments provided critical data for analyzing the relationship between tympanic membrane perforations and hearing impairment in the study population..

Data Analysis

Data were analyzed using SPSS version 20. Descriptive statistics (mean, standard deviation) were used for numerical data, while categorical data were analyzed using frequencies and proportions. Paired t-tests, Chi-square tests, Pearson’s correlation, and linear regression analyses were used to assess the correlation between TM perforation size, site, and hearing loss. A p-value of ≤ 0.05 was considered statistically significant.

Ethical Considerations: Ethical approval was obtained from the Research and Ethics Committee of UPTH. Informed consent was obtained from all participants, with full disclosure of the study procedure.

Results

Table 1: Summary measures of the area of tympanic membrane (TM) perforation in percentages

As seen in figure 1, the distribution shows the various classes of the sizes of tympanic membrane perforation. The class small accounted for 72.9% while large was 2.9%. Very large perforation was not seen in any ear.

Figure 1: Distribution of the categories of percentage area of tympanic membrane perforation.

As shown in figure 2, there is a correlation between the size (area) of tympanic membrane perforation and air conduction PTA values. This is reflected in the p-value of 0.001 being significant and the Pearson’s correlation r = 0.376 showing a weak correlation.

Figure 2. Correlation between area of perforation (%) and air conduction hearing threshold (dB).

From figure 3 below. There is no correlation between size of tympanic membrane perforation and bone conduction values as illustrated with the p-value not being significant 0.949 and the Pearson’s correlation also showing no correlation with values of r=0.008

Figure 3. Correlation between area of perforation (%) and bone conduction hearing threshold (dB).

From the illustration below as shown in figure 4, the means area of tympanic membrane perforation was lest among patient with normal hearing and highest among patient with mixed hearing.

However, the p-value was not significant.

Figure 4: Error bar chart showing mean area of tympanic membrane perforation across category of hearing loss in the affected ear.

Table 2: Number of segments involved in tympanic membrane perforation

Figure 5: Location of perforation among the patients with only one quadrant perforation (N=36).

Table 3: Tympanic membrane location and hearing threshold (dB)…….. (N=36).

As demonstrated in figure 6, there is no correlation between air conduction and the number of quadrants involved. The p-value of 0.066 is not significant and spearman’s correlation value of 0.221 signify no correlation.

Figure 6. Correlation between number of segments of tympanic membrane location and air conduction hearing threshold.

From figure 7 below, there is no correlation between bone conduction and the number of quadrants involved. The p-value of 0.368 is not significant and spearman’s correlation value of 0.221 signify no correlation.

Figure 7. Correlation between number of quadrants perforated bone conduction hearing threshold.