|Year : 2011 | Volume
| Issue : 1 | Page : 4-7
A study on the relevance of preoperative assessment of Eustachian tube function in myringoplasty
Apoorva Kumar Pandey1, Subhash Chandra Gupta1, Mangal Singh1, Debashish Sharma2
1 Department of ENT and Head-Neck Surgery and Social Medicine, M.L.N. Medical College, Allahabad, India
2 Department of Preventive Medicine, M.L.N. Medical College, Allahabad, India
|Date of Web Publication||11-Oct-2011|
Apoorva Kumar Pandey
Department of ENT and Head-Neck surgery, SGRR IM and Health Sciences, Dehradun
Source of Support: None, Conflict of Interest: None
Aim : Pathophysiology of Eustachian tube significantly affects the result of middle ear reconstructive surgery. The aim of this study is to ascertain the relevance of preoperative assessment of tubal function on the results of myringoplasty and to correlate the outcome of surgery with the tubal function gradings. Materials and Methods : A total of 58 cases of dry central perforation of tympanic membrane were divided into two groups. In control group A, pre-operative Eustachian tube function was not checked. In Test group B, pre-operative Eustachian tube function was checked by modified inflation-deflation test using impedance audiometer. Results : Success was assessed at 4th month postoperatively on the basis of intact drum. The results between both groups were compared using Chi-square test. There was no statistically significant difference (P< 0.05) between the control and the test group. Conclusion : The capability to reduce an applied negative pressure correlates well with the successful result of a tympanic membrane graft. However, failure to equilibrate negative pressure does not discriminate between success and failure of this operative procedure.
Keywords: Eustachian tube, Modified inflation-deflation test, Myringoplasty
|How to cite this article:|
Pandey AK, Gupta SC, Singh M, Sharma D. A study on the relevance of preoperative assessment of Eustachian tube function in myringoplasty. Indian J Otol 2011;17:4-7
|How to cite this URL:|
Pandey AK, Gupta SC, Singh M, Sharma D. A study on the relevance of preoperative assessment of Eustachian tube function in myringoplasty. Indian J Otol [serial online] 2011 [cited 2019 Sep 21];17:4-7. Available from: http://www.indianjotol.org/text.asp?2011/17/1/4/85783
| Introduction|| |
We are at this instance of evolving otological journey focusing special attention towards the middle ear reconstructive procedures. Otologists equitably ascribe that adequate eustachian tubal function is one of the necessary pre-requisites for successful myringoplasty and tympanoplasty surgery. ,, Difficulty stems from disorders of the Eustachian tube More Details influencing the pathogenesis and course of middle ear disease and its medical and surgical treatment; hence, the ability to measure its ventilatory function by a method based on underlying morphological and physiological factors becomes of unsurmountable importance. When exploring for ways to improve the long range surgical success rate for tympanoplasties, it intrigued the otologists to search possible methods of predicting the results of reconstructive middle ear surgeries. Holmquist et al, in cases with chronic otitis media, were the first to study the relationship between Eustachian tubal function, size of mastoid air cell system, and healing. 
The aim of this study is to find the relevance of pre-operative assessment of Eustachian tube function on the results of myringoplasty and to correlate the outcome of surgery with the tubal function gradings.
| Materials and Methods|| |
The present study included 58 cases of chronic suppurative otitis media (CSOM), inactive stage (tubotympanic type) planned to undergo myringoplasty. All patients selected were those who came to ENT department during the period from August 2004 to November 2005. A detailed history was taken and a thorough ear, nose and throat examination was done.
Control group A consisted of 27 cases of dry central perforation, where pre-operative Eustachian tube function was not checked. Test group B consisted of 31 cases of dry perforation, where pre-operative Eustachian tube function was checked by modified inflation-deflation test using impedance audiometer. Hearing was evaluated by pure tone audiometry and correspondingly correlated with tuning fork tests.
Modified inflation-deflation test evaluates both active and passive function of the Eustachian tube (ET). The middle ear is insufflated with air under positive pressure, until the ET spontaneously opens. Then the pump is manually stopped and air is left to discharge through the ET until the tube closes passively. The pressure at which the ET is passively forced open is called the opening pressure, and the pressure at which it closes passively is called the closing pressure. Active tubal function can be assessed by applying positive and negative pressure to the middle ear, while the patient subsequently attempts to equalize applied pressure by swallowing. The residual negative intratympanic pressure after repeated swallowing in order to equilibrate applied negative pressure of -200 da Pa, below which the Eustachian tube cannot open is considered as the simplest and most precise parameter of tubal ventilatory function.
The tympanometer used for modified inflation-deflation test was Siemens model SD 30. The normal Eustachian tube opens with almost every swallow, and a negative or positive pressure applied to the middle ear is reduced in steps until equalization is complete. This normal reduction does not occur in the tube, which has a congenital, anatomical or pathological abnormality affecting its normal function. In such cases, the fall in pressure eventually stops at a level at which, with further swallowing, no reduction of pressure occurs. The actual measurement cannot last for more than 4 mins (240 seconds) at the most. Patients were classified in group B according to the criteria given [Table 1].
|Table 1: Tubal function gradings according to residual negative pressure|
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A regular post-operative follow-up was carried out. Final analysis was done after two to six months (average four months). Otological examination concerning residual/reperforation (site / size), discharge, position of graft, mobility on valsalva / seigelization, tuning fork tests, pure tone audiogram was noted .
| Observations|| |
All the 58 cases underwent a post-aural route, inlay technique myringoplasty using temporalis fascia graft under local or general anesthesia. Out of total 58 cases, 6 patients did not come at follow-up so all the final calculations were based on 52 cases (n=52). Surgical success was evaluated on the basis of intact drum two-six months (average four months) post-operatively. Out of total 52 cases, 38 cases (73.08%) had intact drums at their regular follow-up. 14 cases (26.92%) had residual or reperforations.
Success rate was assessed in group A in which no tubal function was checked. Total patients were 27, but 2 patients did not come at follow up. So the final analysis was done on 25 patients in this group. Surgical success was correlated to pre-operative Eustachian tube function in group B in which tubal function was assessed by impedance audiometer. Total number of patients in this group was 31 but only 27 cases reported regularly till the final follow-up. These further 27 cases were divided according to their respective grades of tubal function. Surgical success was assessed by their healed drum on otoscopic examination [Table 2].
|Table 2: Surgical success in group 'B' correlated with pre-operative tubal function as measured by impedance audiometer using modified inflation deflation technique|
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The results of group A were compared to that of group B using Chi- square test (χ2 =0.92). P value was found to be less than 0.05 indicating that there is insignificant difference between the results of two groups [Table 3].
Overall assessment of hearing improvement among successful cases was also done. Maximum reduction in air-bone gap was 21 dB and minimum reduction was 5 dB. Pre-operatively, there were majority (66.67%) of patients having air-bone conduction gap >21 dB. 12.35% cases had air-bone gap between 0-10 dB and 20.98% had gap between 11 and 20 dB. Post-operatively, majority (36.67%) of patients were having air bone conduction gap between 11 and 20 dB. 35% of successful cases had air-bone gap >21 dB and 28.33% cases had air bone gap between 0 and 10 dB. Clearly there was improvement in hearing status among successful cases.
| Discussion|| |
The modern era of myringoplasty dates back from the contribution of Wullstein and Zollner who repaired tympanic membrane with full thickness or split thickness skin. , In 1960, Heermann began to use temporalis fascia as graft material and since temporalis fascia continues to be the material of choice for the reconstruction of the tympanic membrane.  Besides the type of graft material used, several other factors adduced to affect the success rate of myringoplasty are size and site of perforation, stage of CSOM -quiescent/active, condition of middle ear mucosa, Eustachian tube function, age of the patient, tympanosclerosis in remaining part of the tympanic membrane, status of opposite ear, technique of operation and experience of operating surgeon.
The physiological function of the tube is divided into three parts: pressure equalizing function, drainage function and protective function. Adequate function of the Eustachian tube undoubtedly remains as one of prerequisites for re-establishing a closed aerated tympanic cavity in tympanoplasty. Controversy mounts when it comes to precisely measure this function and to whether the testing methods available are adeptly capable of giving useful clinical information. [,8]
Mink said about his experience on tubomanometry that, this test was designed to examine the patient's ability or inability to equalize a negative or positive pressure in the tympanic cavity by swallowing.  The test has two advantages: it is relatively simple and it closely simulates the main physiological function of the tube.
The number of ears with the ability to equalize the negative intratympanic pressure completely or partially has varied from 7.5  to 70% in different pathological (chronic otitis) materials, the mean being 46% .  In our series, there were 37.03% cases completely equalizing -ve pressure and 14.83% equalizing partially and 48.14% were unable to equalize -ve pressure completely (group B).
Mackinnon measured ventilatory function of the Eustachian tube in eighty cases prior to myringoplasty.  Three grades of good, moderate and poor Eustachian function are described depending on the residual negative intratympanic pressure, 80% of cases operated on with good and moderate grades of Eustachian function had a healed TM, a hearing improvement, and an air containing middle ear cavity. However, only 29% of cases operated on with poor Eustachian function had a similarly successful result. It is suggested that this test is useful regarding a decision about the optimum time for closure of a perforation by myringoplasty or other form of tympanoplasty.  In our series, there were 80% healing rates in normal ET functioning, 75% in hypofunction group, 53% in non- functioning groups.
Miller and Bilodeau assessed pre-operative tubal function by tubal manometry in cases destined for myringoplasty. They reported 88% success rate in good tubal function cases, 33% in impaired function cases, and 0% in non-functioning tubes. They interpreted that poor tubal function does not serve as a contraindication to surgery, as it may be reversible provided that adequate removal of diseased foci could have been achieved. 
Fateen et al concluded in their study that 95.6% of ears with good post-operative tubal function resulted in successful graft uptake, whereas only 42.8% of ears with poor postoperative tubal function healed well emphasizing the essentiality of Eustachian tube function for successful graft uptake.  In another study comprising of 269 dry ears with sequelae to chronic otitis and drum perforation, positive valsalva was present in 64% preoperatively and it improved up to 87% postoperatively. Hearing improvement was also achieved less satisfactorily in ears with -ve postoperative valsalva as compared to ears with +ve valsalva, indicating the indubitable role of tubal function in chronic otitis both from pathogenetic and surgical standpoint. 
Role of Eustachian tube function in successful outcome of myringoplasty remains controversial. Some studies have demonstrated a correlation between normal pre-operative tubal function and successful grafting, [15-17] but other studies have failed to confirm this. ,
Takahashi et al analyzed tubal function using an inflation-deflation test in 78 cases with non-cholesteatomatous chronic otitis media, without ossicular damage and asserted that patients having poor pressure equalization ability showed considerably poor surgical outcomes, poor hearing restoration, spontaneous perforations, or persistent otorrhoea. 
Holmquist and Lindeman explicitly stated that ears with "poor" pre-operative ET function have a higher risk for atelectasis with retraction pockets, or secretory or adhesive otitis media.  Ears with pre-operative "poor" ET function must be scrutinized more precisely after surgery, as compared to those with "good" pre-operative ET function, to possibly prevent such complications. Choi et al concluded that tubal function as evaluated by inflation-deflation method was a good indicator of well aerated tympanum, as well as of better postoperative hearing attainment. They further stressed that tubal function can be used in planning and appropriate selection of surgical methods like epitympanic obliteration or cartilage tympanoplasty. 
Virtanen et al. (1980) stated disparagingly, in dry drum perforations and normal tympanic mucosa, elaborate Eustachian tube function tests are futile and it is the faultless surgical technique that ultimately decides the result. In our series too, there is 80% healing rate in control group A irrespective of knowing the status of their pre-operative Eustachian tube function. 
Cohn et al studied the relationship between Eustachian tube function and tympanoplasty and concluded that capability to neutralize an induced negative pressure is indubitably associated with successful tympanic membrane closure. However, compromise or even total failure to neutralize an induced -ve pressure does not preclude successful grafting of the tympanic membrane; nor should such failure to reduce -ve pressure by this technique stress as a contraindication to surgery. 
| Conclusion|| |
Surgical success of middle ear reconstructive surgery is adjudged on the basis of intact drum aimed to improve hearing and to prevent otorrhoea. Pre-operative Eustachian tube function testing is not strictly a pre-requisite before myringoplasty but it should be a part of pre-operative evaluation, hence to observe more closely poor tubal function group post-operatively. Whereas the capability to reduce a negative pressure correlates well with successful take of a tympanic graft. Likewise the inability to equilibrate negative pressure does not serve as a contraindication to surgery.
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[Table 1], [Table 2], [Table 3]