Does Eustachian tube function affect the outcome of tympanoplasty?

Eustachian tube function has been regarded as a significant factor in the successful outcome of tympanoplasty. Eustachian tube dysfunction has been attributed to many diseases of middle ear cleft ranging from otitis media with effusion to unsafe chronic otitis media. The aim of this study is to evaluate the effect of Eustachian tube function on outcome of tympanoplasty in safe chronic suppurative otitis media patients and detect the correlation between the type of the used graft and the outcome of tympanoplasty. This study included 60 randomly selected patients diagnosed with safe chronic suppurative otitis media. Eustachian tube function was tested with tympanometry and Toynbee’s test. All patients underwent tympanoplasty type I. Successful statistically significant outcome was observed in 83.3 % of patients with normal eustachian tube function, while in 60 % of patients with eustachian tube dysfunction (p < 0.05). Eustachian tube function significantly affects the outcome of tympanoplasty surgery. No significant correlation was noted between the type of the used graft and the outcome of tympanoplasty.


Background
Eustachian tube (ET) normal function is crucial in maintaining the middle ear aeration and middle ear pressure. ET dysfunction may lead to middle ear diseases as well as affects the postoperative outcome in patients with chronic suppurative otitis media. Preoperative assessment of the ET function is important to anticipate the postoperative outcome. Normal ET function is essential for restoration of the integrity middle ear and normal hearing [1].
Tympanoplasty is a procedure to eradicate the middle ear disease and to reconstruct the hearing mechanism. The aims of tympanoplasty are to provide a dry ear and to restore hearing as much as possible. Many factors have been attributed for the success, out of which ET function is considered one of the most important [2].
The reported success rates of tympanoplasty surgeries were higher in patients with normal ET function. On the other hand, success rates were lower in patients with ET dysfunction. Therefore, preoperative assessment of the ET function can improve the outcome by choosing the proper surgical technique for each case [3].
The aim of the current study is to evaluate the effect of Eustachian tube function on outcome of tympanoplasty in safe chronic suppurative otitis media patients and detect the correlation between the type of the used graft and the outcome of tympanoplasty.

Methods
This interventional study was carried on 60 patients having the diagnosis of tubotympanic type of chronic suppurative otitis media (CSOM). Patients were randomly selected from outpatient clinic of Otorhinolaryngology department at Faculty of Medicine, Cairo University, Egypt.
Inclusion criteria included CSOM (tubotympanic type) of more than 3 months duration. Exclusion criteria included patients younger than 14 years or older than 50 years, history of previous ear operation, atticoantral CSOM, acute infection, general diseases as diabetes mellitus and nasal or nasopharyngeal manifestations (as allergic rhinitis, chronic sinusitis and adenoids). The study was approved by the Ethical and Research Committee. Written informed consents were obtained from all participants or their parent or legal guardian in the case of children under 16 years. Full otorhinolaryngological examination was performed including full history taking.
Audiological evaluation was done using Clinical audiometer Madsen Itera II (Natus, Denmark) calibrated according to the international standard organization (ISO) standard, in a sound treated room (Amplisilence model E), and a TDH 39 earphones. Tonal audiometry was done in the frequency range 0.25 -8 kHz. Speech audiometry: speech reception threshold (SRT) using Arabic spondee words [4] and word discrimination score (WDS) using Arabic phonetically balanced (PB) words [5]. Immittancemetry was done using Madsen Zodiac 901 (Natus, Denmark), calibrated according to the ISO standard. Tympanometry and Eustachian tube function (The Toynbee's test) were done. The impedance audiometer (Toynbee's test) assesses the ET function in perforated tympanic membrane. It is programmed to increase and decrease the middle ear air pressure. Then, the patient is asked to swallow repeatedly. The change in in the middle ear pressure is recorded with each swallow. The pressure change is represented graphically as a step ladder graph if the ET function is normal. If pressure persists after five swallows, then ET dysfunction is diagnosed (Fig. 1). All patients underwent underlay tympanoplasty type I under general anesthesia with temporalis fascia or cartilage (tragal or conchal) grafting through post auricular approach and underlay technique. Follow up visits were scheduled at the 1 st and 2 nd weeks postoperatively then at the 6 th postoperative month. The outcome was considered successful if the graft was completely healed at the 6 th postoperative month.
Sample size calculation was done using the primary outcome (the success of the middle ear reconstructive surgeries). The calculated minimum proper sample size was 27 participants in each arm to be able to reject the null hypothesis with 80 % power at α = 0.05 level using one way analysis of variance and test ratio between the two groups at 1:1 and with an accommodated 20 % dropout rate. Sample size calculation was done using MedCalc software version 19.1 (MedCalc Software Ltd, Belgium).
Data were coded and entered using the statistical package for the Social Sciences (SPSS) version 26 (IBM Corp., USA). Data was summarized using mean, standard deviation, median, minimum and maximum in quantitative data and using frequency (count) and relative frequency (percentage) for categorical data. For comparing categorical data, Chi square (χ2) test was performed. Exact test was used instead when the expected frequency is less than 5 [6]. p values less than 0.05 were considered as statistically significant.

Results
This prospective study was done on 60 patients diagnosed as tubotympanic CSOM. Age ranged between 15 to 40 years old. Males to females were 20:40.
Patients were divided into two groups according to ET function. First group included 30 patients with normal ET function (50 %) and the second group included 30 patients with ET dysfunction (50 %). Both groups were then subdivided into 2 equal subgroups, 15 patients each, according to the used graft whether temporalis fascia or tragal / conchal cartilage. All patients underwent tympanoplasty type I.
The outcome was recorded at the 6 th postoperative month. Out of 30 ears with normal ET function, graft was healed in 25 ears (83.3 %) and failed with residual perforation in 5 (16.7 %) ears. Moreover, out of 30 ears with ET dysfunction, graft was healed in 18 (60 %) ears and failed in 12 (40 %) ears. Results were statistically significant (p value = 0.045) ( Table 1).

Discussion
In the current study, statistically significant correlation was detected between ET function and result of the tympanoplasty type I surgery (p value < 0.05). Graft uptake rates were better in the normal ET function group compared with ET dysfunction group, with success rates of 83.3 % and 60 % in both groups respectively (Table 1). Prasad et al. in 2014 [7] reported similar results, as graft uptake in normal ET function patients was 80 % versus 50 % in those with ET dysfunction. Sen et al. (1998) [8] described graft uptake rates of 80 % and 66 % in normal ET function and in ET dysfunction respectively. Cohn et al. in 1979 [9] stated that those with normal ET function showed successful outcome in 95 % and 69 % in those with ET dysfunction. Tos in 1998 [10] and Priya et al. in 2012 [11] testified that the ET function is an important influence in the successful outcome of tympanoplasty due to its role in ventilation of the middle ear.

Type of graft and its effect on healing
In this study, no significant correlation was noted between the type of the graft and the outcome of tympanoplasty with p value > 0.05 in both groups. These results agree with the study of Lyons et al. in 2016 [12] who observed that there was no evidence of superiority of cartilage graft over temporalis fascia graft in tympanoplasty type I. On the contrary, Jalali et al. in 2017 [13] reported that cartilage graft seemed to show a higher graft healing rate compared with temporalis fascia graft. Moreover, Mohamad et al. in 2012 [14] described that tympanoplasty using cartilage graft with or without perichondrium had better morphological outcome than temporalis fascia graft.

Conclusion
ET function has a significant impact on tympanoplasty outcome. Pre-operative ET function evaluation should be done routinely prior to middle ear surgery. Moreover, no correlation has been found between the type of used graft and the outcome of tympanoplasty.