Tympanometric screening for Otitis media of paediatric patients with respiratory tract infection in rural setting a prospective observational study

Introduction: Early identification of hearing impairment in childhood is imperative, as even a mild hearing loss can have long term consequence on the development of the Central Nervous System. Many children develop transient, fluctuant deafness due to Middle ear effusion, especially during episodes of Common cold. In this research we try to develop a Screening protocol using Impedance Audiometry for early identification of Middle ear effusions. Materials and Methods: Children between 7 months to 6 years of ages, with no previous history of hearing impairment or ear disease, who were suffering from Upper respiratory tract infection (Common cold) were selected as targets of screening. These children were then subjected to a Screening Tympanometry. A simple, quick and accurate method of screening for Middle ear fluid was “Peak” or “No peak” approach was employed to judge the curves. If a curve was obtained (similar to Jerger's classification-type “A”) child was deemed to have “Pass”. A type “B” curve was deemed highly positive and was labelled “Fail+” and any other trace like type “C” or just reduced type “A” or “As” labelled just “Fail”. Otoscopic and endoscopic examination and diligent search was carried out for signs of Middle ear effusion and confirmation was done. This was cross checked by 2 authors (First and third author) and findings confirmed. Results: Dervan child screening protocol is 91.67% (92%) sensitive and 94.23 (94%) specific is detection of Middle ear effusions. Conclusion: Dervan child Middle ear effusion protocol can be used in a cost efficient, scalable and sustainable method of screening children for Middle ear effusion. Tympanometry in selected high risk population is an accurate and reliable test for detection of Middle ear effusion


Introduction
Early Identification of Middle Ear Disease in Children is important because Hearing impairment even mild to moderate levels can lead to irreversible consequence on the development of the Nervous system. Despite large scale use of Otoacoustic Emissions for screening of Newborns and Infants, most children will develop transient Hearing impairment which is present only during episodes of common cold (Upper Respiratory Tract Infection URTI). Many children who develop episodic Middle ear effusion will suffer from variety of fluctuant deafness for weeks and months, which can impact the development of the Nervous system [1].

Materials and Methods
Tympanometric Screening is a strategy to detect Children who have a middle ear effusion from those who do not in a pain-free, safe, scalable, quick, and cost-effective manner. The main objective of this Tympanometric screening is to The percentage of cases correctly diagnosed by the test is called its Sensitivity, and the percentage of negative results from the tests in normal subjects is called the Specificity of the test. This ASHA method of Impedance screening suffers from low specificity, where in a large number of normal children also get referred for further evaluation [3].

Historical Tympanometric screening programs
ASHA guideline (1997) for screening children from 7 months of age to 6 years uses the following criterion [4]  There were no ethical issues involved as the test was conducted free of cost for the patients and Tympanometry is non invasive, rapid, painless and objective. Staging system of Pars tensa retraction suggested by Sade was used to clinically grade the degree of retraction. Neither treatment nor surgical intervention was included in this study.

Inclusion and exclusion criteria
In neonates the standard 226-Hz tympanograms donot provide correct diagnostic information due to immaturity of the Ossicles, horizontal orientation of the Tympanic membranes [6]. In addition the Tympanogram of Neonates is claimed to be of a notched "M" shape [7]. Neonates were thus excluded from the study.
For selection of the screening the following inclusion criteria were used.
1. Children between 7 months to 6 years of ages.
2. Any hearing loss beyond 55db was deemed not due to Serous Otitis media and was excluded from this protocol. Children with any evidence ear discharge were excluded from the study as these would be cases of Chronic Otitis Media (COM / CSOM) not a subject of this current research.

Fig-1: Dervan child screening protocol for detection of Middle ear effusion and transient deafness
Result Table I depicts demographic characteristics of participants in this Screening protocol. Children of from 7 months of age to 6 years, who attended the Paediatric medical clinic, for symptoms of common cold (which is the ideal time for effusions to manifest), having normal hearing child (No previous ear pathology) and no obvious ear canal pathology observed with a common pen-torch light (affecting the test) were inducted into the first stage of Screening.
A total 133 children were examined at Paediatric clinic, 33 were rejected in stage 1 and100 children were included for the study stage 2 The average age was 4.5 years (Standard deviation of 0.8 years), and the majority of suffering patients were female (68%). There were no observed statistically significant differences in age, sex across disease types.   A total of 133 cases were chosen, from which 33 were rejected by the paediatrician on the basis of inclusion criteria. These were as follows: 1. Children between 7 months to 6 years (ASHA guideline 1997), 2. Suffering from cold which is ideal time for effusions appear, 3. No previous hearing or ear problem and 4. No obvious ear pathology seen with a pentorch. Hundred children were included in this screening program, amongst which 55 children had an immediately visible peakon Impedance audiometer (Jerger Type "A"). These children were deemed "Pass" in the screening.
Those who did not have a visible reading on Tympanometry were deemed failed in the screening and were most likely suffering from permanent or transient middle ear pathology.A type "B" trace was deemed highly positive and labelled as "Fail+" and any other trace like type "C" or just reduced type "A" or "As" was labelled as "Fail". "Fail" category those with a "Fail" were examined with Otoscope and diagnostic endoscope.
Diligent search was done for signs of Middle ear effusion (illustrated in the chart) like meniscus sign, hair line sign and air bubbles in middle ear. Any positive finding was confirmed by a consensus between two surgeons (Principal author and Co-author). Thus Screening Impedance audiogram was compared with a gold standard test of direct visualization of the Middle ear effusion.

Discussion
Aetiology and patho-physiology of paediatric middle ear diseases and conductive deafness-There is a phase differential between sound waves travelling in the air column and fluid filled cochlea which is site of perception of sounds [13]. This phase differential is overcome by the transformer action of the middle ear, tympanic membrane and ossicles [14]. Thus acting as an amplifier of sound and transmit it to the inner-ear fluid. If this conduction pathway is obstructed sound can still travel via the skin and through the bones of the skull and directly stimulate the cochlea [15]. This occurs at the cost of significant energy loss. The most common causes of conductive hearing loss include impacted wax in the external canal, otitis media, which can be infected fluid (chronic Suppurative otitis media C.S.O.M) or transudation fluid (serous otitis media S.O.M/ middle ear effusion) accumulating in the middle ear [16]. With long standing cases chronic otitis media there is a risk of development of a cholesteatoma, which is skin lined, sac like structure. Cholesteatoma is notorious for erosion and destruction of the bone eventually leading to major complications like brain abscess and meningitis [17].The vast majority of cases of Otitis media have a benign clinical course, Otitis Media can lead totransient and permanent deafness, developmental delays or serious extra-cranial or intracranial complications likebrain abscess and meningitis [18].
Middle ear infections leading to delayed speech and language development, academic performance in schools, psychological development, neurological "soft signs" and cognitive ability has been studied extensively in western population and many papers published at the crux of the pathology [19]. But no such research exists for the Indian especially Konkan children. As such due to difference in demographics of the people it is expected that patter n of presentation of Otits media would be different and more subtle as compared to their western cohorts.
The most common type of acquired hearing loss is conductive hearing loss due chronic middle ear effusion also known as Secretory Otitis media. The age distribution in children described in literature is bi-modal with first peak at around 2.5 years of age, then again at around 4.5 years of age when children enter the school. By one estimate about 30% of preschool children are affected in winter season [20]. The American Academy of Paediatrics estimates an incidence of over 5 million middle ear infections in American children, leading to about 30 million visits to clinics per year. Over 10 million annual antibiotic prescriptions are handed out for treatment of Otitis media. This is disease burden of middle ear effusion [21].
Acoustic Reflex Testing-Acoustic reflex detects the increase in the impedance of the middle ear in response to contraction of the Stapedius muscle within 10 ms, brought about in response to a loud sound of more than usually 80 dB or higher [22]. The afferent limb of this reflex is the Cochlea and Vestibulo-cochlear nerve, the reflex centre is located in the brain stem and efferent limb is via the facial nerve. The vertical segment of facial nerve supplies the Stapedius muscle; the nerve to Stapedius branch is proximal to the geniculate ganglion of Facial nerve. Same ear and opposite ear can be stimulated with sound and impedance increase recorded this is called uncrossed (ipsilateral) acousticreflex andcrossed (contralateral) acousticreflex test respectively [23].
This reflex becomes absent in presence of slightest degree of hearing loss, hence by itself is a sensitive test for detection of deafness. Same sided or uncrossed (ipsilateral) acoustic reflex test is easy to perform and can be done by the same probe which is used to record Tympanometry. This test was done and reflex was studied. If Stapedius muscle contraction within a time span of 10 ms was elicited this test was designated as "pass" and formed another criteria for screening for Conductive hearing loss and middle ear disease [24].

Fig-2: Uncrossed (ipsilateral) Acoustic Reflex Testing (drawn by first author) [24]
Since the test subjects were selected at random from children who attended the paediatric clinic there is no reason to assume external validity of the protocol especially on Konkan population for which this was developed. Reproducibility or reliability is open to further studies at our department or other hospitals which will validate this parameter.
The sensitivity of a protocol is its ability to accurately screen population who do have trait. The sensitivity of a protocol is its ability to accurately screen out or eliminate population who do not have trait or disease risk [28].

Contributions by three authors-
The senior author and the third author were involved in the supervised audiological testing, collection of data and statistical analysis of the data. The second author being the Paediatric specialist provided technical insights into the clinical framework of the research. First author wrote the manuscript which was discussed and agreed upon by the other authors.

Conclusion
Middle ear infections leading to delayed speech and language development, academic performance in schools, psychological development, neurological "soft signs" and cognitive ability has been studied extensively in western population and many papers published at the crux of the pathology But no such research exists for the Indian especially Konkan children. As such due to difference in demographics of the people it is expected that patter n of presentation of Otits media would be different and more subtle as compared to their western cohorts. Dervan child Middle ear effusion protocol can be used in a cost efficient, scalable and sustainable method of screening children for Middle ear effusion. Tympanometry in selected high risk population is an accurate and reliable test for detection of Middle ear effusion. This reproducibility of this protocol has to be validated by further studies in our hospital and elsewhere.