INTRODUCTION

Accumulation of non purulent fluid in middle ear cleft is one of the commonest causes of hearing disability in children. Though it is described with various synonyms like catarrhal, exudative, seromucious, secretory, nonsuppurative otitis media but the most widely accepted terminology is otitis media with effusion (OME) (1).

The cause is basically eustachain tube dysfunction and nasopharyngeal disproportion. Nasopharyngeal disproportion is due to craniofacial abnormality and adenoid hypertrophy. Disease peak at age of 2 years and 5 years (1,2). OME can be De novo or following an episode of acute otitis media. 20-50% of children between ages 3 - 10 years will have at least one episode of OME. By age of 2 years 40% of children will have OME while at 11 years of age only 1% has it (1,3). 90% OME has spontaneous resolution and most of them by 3 months while rest 10% persist with multiple squeale (1). The incidence of OME in Nepal is not studied much but according to one study it is 1.65% in general Nepalese population (4).

There is growing evidence of correlation between OME and speech, language and cognitive development. Clinically diagnosed cases of Otitis Media with Effusion are investigated with tympanometry and pure tone audiometry. Patients with type B curve planned to have ventilation tube insertion after 3 months if it does not resolve by that time. It is because 50% of cases will resolve in 3 months by its own. Myringotomy with or without Ventilation tube insertion is best modality of management in such persisting OME (5). Fluid or glue if obtained in myringotomy is the gold standard method of diagnosing the condition as well. But in clinically diagnosed cases of OME can have thick or thin fluid on myringotomy or even can have dry tap.

The aim of study is to assess different types of fluid after myringotomy in OME and also to assess the Pre Operative Tympanogram in Patients undergoing Myringotomy. By comparing them this study focuses on accuracy of predicting type of myringotomy fluid by tympanogram.


METHOD

It is a retrospective longitudinal Study conducted in the department of ENT-Head Neck Surgery, TU Teaching Hospital, Kathmandu, Nepal from 1st 0ctober 2005 - 30th September 2007. All Pediatric patients (< 12 years) of either sex who underwent myringotomy with or without VTI during that period in TUTH were included in this study. Patients with inadequate recordings were not included.

Tympanometry (Interacoustic AS, Assens, DIC-5610, and Denmark) and pure tone audiometry (Hughson's and West lake method) was done 1 week prior to surgery planned. Myringotomy was done under General Anaesthesia. Data analyzed using Chi Square test.


RESULTS

Total no. of ears that underwent myringotomy was 51. Out of which 26 were of male children. Fluid was found during myringotomy in 37 ears while rest had dry tap. Most of the children (56.8%) were in 5-8 years of age (Figure 1, Table 1).

Figure 1. Showing age distribution of study group.

Tympanogram analysis showed B type curve in more than 90 % of ears (Figure 2). Curve on tympanometry were Type A - 3 (5.8%); Type B - 46 (90.2%); Type C - 2 (3.9%). Dry tap rate was 27.6%

Figure 2. Showing different types of tympanogram curves and correlating with different Myringotomy fluid.

Out of 37 ears with fluid on myringotomy 78.37% had thick fluid and all thick fluid cases had B type of curve (Table 2). The result is found to be significant at 5% level of significance using Chi Square test for correlation of B type curve with thick myringotomy fluid.

Average volume and compliance was tabulated in different types of myringotomy fluid. Though low volume and compliance was found in thick fluid it was not statistically significant using Chi Square test (Table 3).

If OME is defined according to presence of Fluid on myringotomy then according to Table 4 we can interpret Sensitivity of B curve to predict OME: 97.3%. Specificity of B curve to predict Fluid: 28.6%, Positive predictive value: 78.3%, Negative predictive value: 20%.

DISCUSSION

Though OME is a common clinical entity; extensive study in our setup has not been done regarding its investigation with tympanogram. Our centre is a tertiary care centre and it represents whole population. Study do not represent true prevalence of the disease as study was performed in only hospital attending patients - most of OME are asymptomatic.

Among the dated patients - only 35% turned up for surgical treatment - may be resolved or treated outside.

Tympanogram being an objective test and as it can be done in small children it is a good, reliable and reproducible investigation than pure tone audiogram. OME is diagnosed clinically most of the time and confirmed with tests like tympanogram, and myringotomy. Dry tap rate of 27.6% is similar to other studies (1). (34%) Though sensitivity is high but specificity is low (28.6%) which may be due to dry tap despite having fluid in middle ear cavity (very thick fluid, located in dependent areas, Nitrous Oxide action). Various studies have been conducted to correlate different diagnostic modalities.

According to PALMU AND SYRJÄNEN study (6), Sensitivity of the type B tympanogram was 61% and specificity 99% at the sick visit when Pneumatic Otoscopy was used as the reference method for the diagnosis of Otitis media. In SAEED K et al study (7), with tap findings as the standard, sensitivity and positive predictive value of type B tympanogram were 97 and 87%, respectively. This study is similar to our study with good specificity result. HARRIS PK et al study (8) used myringotomy to diagnose and found that the diagnoses provided with pneumatic Otoscopy and tympanometry were both similar, agreeing in diagnosis 80%-100% of the time. In study of OKITSU et al (9) it was demonstrated that the tympanogram pattern depends on the fluid volume and location, air volume of mastoid cavity, intratympanic pressure and eardrum condition. ORJI AND MGBOR study (10) showed that Simple Otoscopy produced 84.4% agreement with tympanometry in detecting OME. The agreement was better in older children than the younger ones (P < 0.05).

Compliance and volume has also been tried to be correlated in SMITH et al study (11). For tympanograms generally, the lower their height and the greater their width, the greater was the probability of associated middleear effusion. Among children > or = 6 months of age, effusion was diagnosed in only 2.7% of ears with tympanometric height > or = 0.6 mL, but in 80.2% of ears with flat tympanograms. But in our study regarding volume and compliance it was not statistically significant.


CONCLUSION

Common type of tympanogram curve in patients with OME is B type, but it doesn't always indicate to have fluid in middle ear. Tympanogram is useful in predicting the nature of the myringotomy fluid.


REFERENCES

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1. Dr. M.S.Resident, Department of ENT and Head and Neck Surgery, T.U.Teaching Hospital, Kathmandu, Nepal.

Instituto: Department of ENT and Head and Neck Surgery, T. U. Teaching Hospital, Kathmandu, Nepal.

Endereço para correspondência:
Dr. Rishi Bhatta
Department of ENT and Head and Neck Surgery, T. U. Teaching Hospital
Kathmandu - Nepal - E-mail: rishi_31@yahoo.com

Artigo recebido em 10 de abril de 2008.
Artigo aceito em 10 de junho de 2008.