Hearing evaluation after myringoplasty

This study was carried out to assess the graft take rate as well as hearing improvement after myringoplasty with temporal fascia graft by underlay technique. Study was done in department of ENT and Head-Neck Surgery of BSMMU, Dhaka Medical College Hospital and BIRDEM from July 2006 to June 2007. Sixty (60) patients were included prospectively for this work. In this study graft take rate was 85% (51 out of 60) and graft failure was 15% (9 out of 60). The age range of the patients was 10 to 50 years. Highest number of patients was in the age group of 21 to 30 years and graft take was also maximum in this age group. Graft take rate of small size perforation (100%) and medium size perforation (93.23%) had more than subtotal perforation (77.77%). Success rate of posterior perforation was maximum (93.75%) followed by anterior perforation (88.23%). In case of approach of operation postaural approach had maximum success rate (88.09%) followed by endaural (75%) and transcanal approach (80%). In this study the mean pre and postoperative air conduction threshold in the successful cases were 34 dB and 24 dB respectively, with a mean audiological improvement of 10 dB. Improvement of mean air bone gap was 11 dB. Of the successful cases hearing was improved in 31 patients (60.78%) and 20 patients (39.21%) showed no significant hearing improvement. From this study it can be concluded that myringoplasty is a valid treatment modality for tympanic membrane perforation.

Among the two types of chronic suppurative otitis media.Tubotympanic variety is the commonest and is called safe variety as the risk of developing complications are less and the name tubotympanic indicate disease of Eustachian tube and tympanic cavity 1 .Tubotympanic disease is always charac-terized by central perforation involving the pars tensa of varying size and shape but with a narrow margin of intact annulus and usually with part or all of the membrane of the malleus remaining 2 .The perforation of the tympanic membrane is associated with aural discharge and hearing loss.
Aural discharge is always mucoid or mucopurulent and varies with upper respiratory tract infection.Discharge is usually intermittent recurring whenever there is a fresh head cold or water enters in to the ear 2 .

Original Article
Bangladesh J Otorhinolaryngol 2010; 16 (1): 23-28     Hearing loss in tubotympanic disease is usually conductive in nature but a few case of sensorineural hearing loss is found 3 .
Hearing loss with intact ossicular chain is approximately 10-30 dB 4,5 .But more when ossicular chain is disrupted.
Myringoplasty is the operation specially designed to repair or reconstruct the tympanic membrane.The earliest reported successful myringoplasty was done by Berthold in 1978, using full thickness skin graft 3 .Since then, myringoplasty has gone through many changes in technique and materials.Shea in 1960, first introduced underly technique for myringoplasty but using vein graft 3 .And autologus temporal fascia used as graft material firstly by Heerman in 1960 3 .
The surgical outcome of myringoplasty is influenced by many factors.The reported success rate of myringoplasty is therefore variable, partly because of differences in the inclusion and exclusion criteria, In a study overall success rate of myringoplasty was 86%.Posterior and inferior perforations had a 98% success rate for repair compaired to only 67% of anterior perforation.The success rate of subtotal perforation closure was (92.5%) 6 .But the poorer results were in younger patients.A study found better success with advancing age 7 .This is due to lower incidence of upper airway infection and better Eustachian tube function in later age and the relative immaturity of system in younger children, Lorenzo Pignataro found better success rate in underlay technique than overly technique 8 .The success rate was 82.3% in the former and 79.1% in the later.
At present, myringoplasty is a common operation in the Otolaryngology Department, having microsurgical facilities.The present study aims to evaluate the surgical and audiological outcome of myringoplasty using underlay technique with temporal fascia graft in selected patients with tympanic membrane perforation and to assess the factors potentially influencing those outcomes.

Methods :
This prospective study was carried out in the department of ENT and Head-Neck surgery of BSMMU, Dhaka Medical college hospital and BIRDEM from July 2006 to June 2007.Sixty (60) cases were selected for this study who underwent myringoplasty using underlay temporal fascia graft.
The assessment of the patients was established on the basis of history, clinical examination and audiometric test per operative assessment and post operative followup was done.The patients were post operatively followed up at weekly interval for 1 st month and Then at the period of three month interval for 1 st year.At the follow up examination, result of surgery was regarded as successful if ear was dry and the tympanic membrane intact and mobile.Audio metric test (PTA and Impedence) were performed after three months and hearing gain or loss was compaired with pre-operative test.The above table shows that medium size perforations were the commonest one and graft take rate was (91.3%) which was more than subtotal perforations (77.77%).Graft take was 100% in small size perforations.Above table shows that most common approach was postaural (70%) followed by transcanal approach ( 16.66%)).There is no gross difference in graft take rate with regard to approach of surgery.seen in 20 (39.21%) patients.Gain or loss of hearing of 0-10 dB was not considered significant.In that sense, no improvement seen in 20 patients.

Discussion:
In this study 60 patients those underwent myringoplasty using underlay technique with temporal fascia graft were studied prospectively after taking relevant history, clinical examination, investigation and follow-up.
In this series the graft take rate was 85% (51 out of 60) and the graft failure was 15 % (9 out of 60).This rate of graft intake is more or less similar to the Kotecha 11 (82%) and Ugo Fish 10 (86%), whereas Eero Vartiainen 12 showed that rate of graft intake 91.2% which is significantly higher than this study.
In Medium size perforations were commonest one in this study and the graft take rate was also maximum in this group (91.3%)Graft take rate of subtotal perforation was significantly less (77.77%).In case of small size perforation graft take rate was 100%.One series showed that the closure rate was reported to be higher in small perforations (74%) than large perforations (56%) 16 .
In this study graft take rate in case of posterior and anterior perforation was 93.75% and 88.23% respectively which was significantly more than that of subtotal perforation (77.77%).The site of perforation statistically affect in our series as has been previously reported by others 13,14 .And higher rate of surgical failure in patients with anerior perforations in comparison to posterior pereforations in this study, may have been due to the more limited vascilarization of the anterior part of the ear drum, limited access to this perforation as well as difficulty in graft placement also.
Surgical approach depended on dimension of external auditory canal, site of perforation as well as surgeon's preferences.In this study graft take rate was sgnificantly greater with postauricular approach (88.96%) than that of endaural (75%) and transcanal (80%) approach.Whenever others series found no difference of graft in take in relation to approach used 9 .
The mean pre and post-operative air conduction theshold in the successful cases were 34 dB.and 24 dB respectively with a mean audiological improvement of 10 dB.Improvement of mean air-bone gap was 11 dB.The best improvement was observed at the frequency of 250-1000 Hz.One might suppose that after a straightforward myringoplasty the air-bone gap should be within a 10dB.This hearing result was achievement in only 60.78% (31 out of 51) of successful operation.Lee et al and Palva and Ransay stated that mean hearing improvement was 8 dB in their series, this improvement is often similar to our study 16,17 .Sheehy and Anderson 15 stated that in most case of chronic suppurative otitis media, even though the ossicular chain may appera normal, there is some factor of scar tissue that prevents total restoration of hearing.However in our series included 20 ears (39.21%) of the successful cases in which hearing was not improved significantly after surgery despite having the eardrum heal perfectly and the middle ear remain aerated.This is similar to the Ugo Fish 10 who showed that hearing improvement occurred in 66% patient.
Inclusion criteria: (a) CSOM-Tubo tympanic type with dry central perforation for at least 3 months but with no other external ear, middle ear or inner ear diseases.(b) No evidence of cholesteatoma.(c) uncomplicated.(d) Age between 11 to 50 year.Exclusion criteria: (a) Evidence of cholesteatoma.(b) Previous tympanic surgery.(c) Traumatic perforation.(d) Severe Tympanosclerosis .(e) Only hearing ear.(f) Chronic otitis externa.(g) Systemic diseases : Diabetes Mellitus, Tuberculosis.

Table - II
Age distribution with relative frequency of graft take rate in different age groups.

Table - III
Relative frequency of graft take rate in relation to the size of perforation.

Table - IV
Relative frequency of graft take rate in relation to the site of perforations (n=60.) this study, lowest and highest age of patients at presentation was 12 and 46 year respectively with a mean age of 29 years.