# Introduction hronic Otitis media (COM) is a permanent abnormality of the pars tens a or pars flaccida, most likely a result of previous acute otitis media, otitis media with effusion or long-standing negative middle ear pressure. 1 The prevalence of chronic otitis media has been reported to be between less than 1% in high-income countries to up to 46% in disadvantaged ethic groups and low-income countries. 2 A prevalence of 1-2% of COM in children in a definite community is considered low and a prevalence of more than 4% is considered high, which also indicates a public health issue requiring urgent attention. 3 Chronic otitis media is the leading cause of preventable hearing loss in children, especially in developing countries. According to the WHO, about 60% of people with COM have clinically significant hearing loss and 90% of these are in developing countries. 3 This is a matter of serious concern especially in children because of the negative developmental and educational impacts caused by hearing loss. Chronic otitis media contributes most to the global burden of hearing loss; hence, eliminating it can potentially reduce the global burden of hearing loss. Recent prevalence of chronic otitis media in Nepalese children is not known, and there is lack of accurate data. The little available data are from either hospital-based or of small cohort studies. More recent data on COM prevalence would help to determine if COM management should be prioritized in the national health care program. Therefore, the main objective of our study is to find out the most recent status of chronic otitis media in Nepalese children and to evaluate corresponding hearing loss. # II. # Methods This is a retrospective study based on data from the medical records of Nepalese Schoolchildren who participated in the school-based ear health programs conducted by our institute over a five-year period from January 2015 through January 2020. Permission to conduct the school-based ear health programs was obtained in writing from the educational authorities of the concerned district and from the individual schools. Schools that provided written consent to conduct ear health program were included in the study. The schools that did not consent were excluded. The medical records contain otoscopic findings of the tympanic membrane, final diagnoses and pure tone audiometry reports of all the children. Detail findings of the tympanic membrane such as the integrity of the membrane, the size and site of perforations, the presence of ear discharge and cholesteatoma were recorded. Demographic details such as age, gender, grade, and ethnicity were also documented. All the confirmed cases of chronic otitis media in children in grades1 through 10along with their pure tone audiometry reports were included in the study. Children diagnosed with acute otitis media, otitis media with effusion, ear diseases other than COM and children with normal findings were excluded from this study. Children with incomplete medical records or missing data were also not included in this study. The school-based ear screening programs were conducted and documented by senior Ear Nose Throat surgeons having more than five years experiences in this community screening work. A Heine Mini 3000 otoscope was used for tympanic membrane examinations. Chronic otitis media was diagnosed when there was a permanent abnormality of the pars tensa or pars flaccida with or without active ear discharge. It is divided into chronic otitis media mucosal and chronic otitis media squamous as per Browning et al. classification of COM. 4 Pure tone audiometry was conducted and documented by an audio-technician using an Arphi Proton SX3 pure tone audiometer. Hearing loss was defined as a pure tone average of four frequencies 0.5, 1, 2, and 4kHz greater than 25dB HL in one or both ears. Data analysis was done using frequency and percentage. The ethical clearance to conduct the study was approved by the Nepal Health Research Council (NHRC) bearing registration number 345/2021 P. # III. # Results Over a period of five years from January 2015 until January 2020, 79,340 children from grades 1 through grade 10 were screened for ear and hearing problems. Out of which, chronic otitis media was diagnosed in 8.04% (n=6,382) children, of which 50.75% (n=3,239) were in boys and 49.25% (n=3,143) in girls. Ages of the children in the study ranged between 4 to 18 years old. The majority of the children with chronic otitis media 60.59% (n=3,867) were aged 11-15 years old with only 3.85% (n=246) of children in the 4 to 5 years age group testing positive for this. Chronic otitis media was seen in 41 Hearing loss was seen in 41.57% (n=2,653) of the children with chronic otitis media, out of which 93.40% (n=2,478) of the cases were conductive hearing loss, which was of mild degree in87.36% (n=2,165), moderate in 9.76% (n=242) and moderately severe in 2.86% (n=71) of the children. Mild conductive hearing loss was the commonest type of hearing loss. This was seen in 81.60% (n=2,165) of the children with COM, whereas, moderately severe mixed hearing loss was the least commonly seen in only 1.31% (n=35) of children with chronic otitis media. 95.60% of children with mucosal-COM had associated hearing loss, whereas only 74.65% of children with squamous-COM had hearing loss. The type and degree of hearing loss associated with different types of COM by age groups are shown in Table 2. # Discussions Despite improvement in public health care in last two decades, there is still a significant burden of chronic otitis media in school-aged children in Nepal. This study shows that the prevalence of chronic otitis media in Nepalese schoolchildren is 8.04%. According to WHO categorization of the countries with disease burden, a prevalence rate of 8.04% places Nepal in the group of the countries with the highest prevalence rates. The high prevalence rate in our study may be caused by increased exposure of the study children to risk factors associated with low socioeconomic strata such as overcrowding, passive smoke and poor nutrition. The largest population-based survey was conducted in 1991 in the general population and found that 7.4% of all Nepalese had middle ear pathology. 5 Following that, a few studies conducted in small pediatric populations have reported prevalence rates of 3.26% by Thakur et al. 6 5% by Adhikari et al. 7 and 10% by Maharjan et al. 8 The relatively low prevalence rate reported by Thakur et al. could be due to differences in sampling size and sampling technique followed in the study. Adhikari et al. conducted the study in urban private schools where socioeconomic status and literacy rates of the parents are high, which could explain the lower number of children with COM in their study group. The school where Maharjan et al. conducted their study mostly enrolled children from one particular ethnic group with poor socioeconomic backgrounds where children had the habit of swimming in dirty water along with their cattle during hot and humid weather in the plains of Nepal, which must have acted as a predisposing factor for chronic discharging ear. Swimming in local pools has been considered an associated risk factor in developing COM. 9 Incomparison, the prevalence of COM in children has been reported as 4.79% in India, 10 5.2% in Bangladesh, 11 7.26% in Malaysia, 12 1.74% in Thailand, 13 2.19% in Korea 14 and 1.65% in Indonesia. 15 In the African countries, lower prevalence rates of COM have been reported such as 4% in Rwanda, 16 5.3% in Malawi, 17 1.4% in Tanzania, 18 and 1.5% in Kenya. 19 Low prevalence rates have been reported in other parts of the globe as well, such as 1.31% in Saudi Arabia 20 and, 0.94% in Brazil. 21 Developed nations such as the US, the UK and most of the European countries have prevalence rates of less than 1%. 3 Contrary to this, high prevalence rates of COM are reported in certain populations and ethnic minorities 22 such as Australian Aborigines, 23 the Inuit 24 and Greenlandic children. 25,26 The wide range in the prevalence rates in these epidemiological studies could be due to differences in exposure to risk factors and access to health care among the study population, population size, ethnic group, sampling technique, and methodology. Differences in the definition and classification of COM used in the study is another important factor for wide variations in the prevalence rates. In our study, the Browning classification of COM was followed because it is the classification of choice used in Nepal. Classifications such as suppurative and nonsuppurative COM are now less commonly used because it is the progression of the same pathological process. Similarly, use of tubo-tympanic as safe and attico-antral as unsafe COM is not recommended any longer since marginal perforations of the pars tensa can also develop complications. 27 Many studies classified COM as tubo-tympanic and attico-antral. 7,28,29 Muftah et al. 9 and Hunt et al. 17 only included the cases with active ear discharge lasting more than 2 weeks with perforated tympanic membrane and excluded the cases with dry perforation and healed tympanic membrane in their study. Other factors such as genetic and environmental factors as a possible cause need to be further studied in certain populations and ethnic minorities. We did not find gender preponderance in our study; COM was almost equal in both boys and girls, which is consistent with other studies. 16,30 Several studies found that older children were more likely to develop COM than the younger children were. 9,17,30 We too found that 60.59% of the COM cases were seen in older children aged 11-15 years and least affected were the youngest children aged five years and younger at 3.85%. COM as well as sequelae of COM such as tympanosclerosis and atelectasis climbed steadily with increasing age suggesting chronicity of the disease. 19 The high prevalence of COM in older children could be result of frequent and untreated or poorly treated cases of acute otitis media and/or otitis media with effusion, which progressed into the chronic phase of the disease. Additionally, traditional practices such as instillation of oil or other liquids to treat ear diseases can lead to continuous otorrhoea progressing the disease into the chronic phase. This trend could explain increasing rates of COM in older children. Chronic otitis media was unilateral in 78.94% (n=5,038) and bilateral in 21.06% (n=1,344) children. This finding is consistent with other studies. 7,16,19,28,31 Bilateral disease are thought to have poor consequence because of associated bilateral hearing loss and poorer surgical outcome. Eustachian tube dysfunction is considered as the main pathogenesis of bilateral disease whereas, in unilateral cases, more localized causes are assumed. Many studies suggest an increased risk of developing COM in the contralateral ear in later years but to evaluate the status of the contralateral ear, a long-term follow up of the children with unilateral disease would be needed. 32,33 In this study, out of 6,382 cases, mucosal-COM was the most commonly observed COM, detected in 30.68% (n=1,958) of the children and the squamous type detected in only 6.80% (n=434). Similar findings were also noted in other studies. 7,10,28,29,31 Contrary to our findings, squamous-COM was more commonly seen in a study conducted by Kumari et al. 34 whereas; Abraham et al. 18 did not find a single case of squamous-COM in their study. Simoes et al. 19 detected squamous-COM in only 0.45% cases whereas 62.51% (n=3,990) of the children had scarring of the tympanic membrane such seen as a thin and healed tympanic membrane, tympanosclerosis, and chalk white patches suggesting previous history of otitis media. A literature review on childhood hearing loss published by Davidson et al. found that children from developing countries had almost double the chances of developing associated hearing loss in COM than in children from developed countries. In our study, we found that 41.57% (n=2,653) of the children with COM were suffering from hearing loss. Similarly, other studies conducted in developing countries also reported increase possibilities of developing hearing loss due to COM. 9,31,34,35 The hearing loss in this study was predominantly the conductive type 93.40% (n=2478) and of a mild degree 87.36% (n=2165). Muftah et al. also observed a similar pattern 9 whereas Anggraeni et al. stated that most of the hearing loss associated with COM in their study group was of a moderate degree. 35 In our study mixed hearing loss suggesting involvement of the inner ear was seen in 6.60% (n=175) of children with COM. This finding demonstrates that the inner ear is vulnerable to chronic discharging ears. [36][37][38][39][40] Significant involvement of bone conduction thresholds were noted in cases with COM. [41][42][43][44] In this study we observed that hearing loss in children with COM increased steadily with increasing age, from 5.69% in <5 year old's to 57.01% in children >15 years old. Sakagami et al. found hearing deterioration was more in the ear with COM than in the normal ear; 0.61dB/year versus 0.13 dB/year. 45 Long-term follow up of COM and its impact on the bone conduction found significant association between duration of COM and presence of involvement of bone conduction. 41,44 It was observed that in mucosal-COM, 94.76%% of the hearing loss was of the conductive type and only 5.23% was mixed type, whereas in squamous-COM mixed hearing loss increased to 17.28%. Opposite to our findings, mixed hearing loss was seen more often in mucosal-COM by kumari et al. 34 In general, a healed tympanic membrane is rarely considered a problem therefore hearing tests are only occasionally done, especially in children. In our study, we noticed that 17.22% of the total hearing loss was seen in children with healed tympanic membranes and 4.60% of which was of mixed type. This finding suggests that scarring of the tympanic membrane should not be taken casually, and it should be further investigated for hearing loss. Similarly, atelectasis of the tympanic membrane was also found to be associated with involvement of the inner ear. 44,46 The size of the tympanic membrane perforation was also found to be related to sensorineural hearing loss. 44,46 In this study, 75.68% of the children had large sized tympanic membrane perforations, but we did not observe similar findings. We did not find any cases of COM with profound hearing loss. This could be because children with profound hearing loss may be deprived of enrolling into the normal education system and were thus under-represented in our study. Poor socioeconomic status has been associated with a higher prevalence of COM due to risk factors such as poor hygiene, overcrowded living conditions and malnutrition. 9,30 This study was conducted in children studying in government schools. The schools run by the state government in Nepal are considered to provide inferior education quality as compared to the more expensive private schools. Therefore, only the most underprivileged children attend government schools. That could explain the higher prevalence rates seen in our study population. Many studies found statistically significant association between COM and socioeconomic status. 11,30,47,48 In school-based studies, prevalence of COM was found more commonly in children studying at rural schools as compare to urban schools; 2.7% versus 0.7%, 15 5.11% versus 2.32%, 28 7% versus 1.8%, 30 and 5.7% versus 4.8%. 48 The wide variation was because these studies were conducted in areas where distinct differences in socioeconomic status such as low socioeconomic status in rural areas and higher status in urban schools was obvious. Lack of access to proper health care in rural settings is another reason for the wide variations in prevalence rates. Hence, improvement in access to affordable health care for children of such communities could decrease the disease burden. This study has both strengths as well as weaknesses. The strength of our study is that it is the largest study documented in a pediatric population in recent years in Nepal, and it explored the detail classification of chronic otitis media and hearing evaluation of all the children with COM. A limitation of this study is that this is a retrospective school-based study. This study only covered schoolchildren; younger children and those who did not attend schools were not included in the study. Although examinations were carried out using an otoscope in respective schools by senior Ear Nose and Throat surgeons with more than five years of experience, early cases of cholesteatoma could have been misdiagnosed as mucosal-COM. Microscopic examination of the ears of all the children was not feasible for the children in this study. This study suggests that chronic otitis media is still a public health issue in Nepal that needs to be addressed urgently to reduce the burden of disease. Findings of our study could help in developing a national health care program focusing on ear and hearing care in Nepal. Measures such as conducting school entrance ear screening, raising public awareness about ear and hearing care, and early treatment of chronic otitis media could prevent hearing loss in most children. V. # Conclusions Chronic otitis media is a public health issue in Nepal. Early diagnosis and proper treatment of chronic otitis media could prevent most of the hearing loss in schoolchildren. Health measures such as school entrance screening, public awareness program and integration of ear and hearing screening in national health care could reduce the burden of disease. 11.84% (n=2,670) of 2Age distributionChildren with media n (%) chronic otitisChildren with n (%) hearing lossType and degree of hearing loss n (%)<5 years old246 (3.85%)14 (5.69%)ConductiveMild13 (92.86%)hearing lossModerate1 (7.14%)5-10 years old1,220 (19.12%)438 (35.90%)ConductiveMild372 (84.93%)hearing lossModerate28 (6.40%)Moderately Severe11 (2.51%)Mixed hearingModerate10 (2.28%)lossModerately Severe9 (2.05%)Severe8 (1.82%)11-15 years old3,867 (60.59%)1,603ConductiveMild1,372 (85.59%) J© 2023 Global Journ als Chronic Otitis Media and Hearing Loss in Nepalese Schoolchildren ## Acknowledgement The authors would like to thank Alan Goldstein for his help in editing the article. * Aetiopathology of inflammatory conditions of the external and middle ear GGBrowning Kerr AG, editor. Scott-Brown's Otolaryngology. 6 th ed. London: Hodder Arnold 1997 * World Health Organization, Prevention of hearing impairment from chronic otitis media: report of a WHO/CIBA foundation workshop 1996 London, U.K. * World Health Organization, Chronic suppurative otitis media; burden of illness and management options 2004 Geneva, Switzerland * Chronic otitis media GGBrowning SNMerchant GKelly ISwan Rc RCanter WSMckerrow Gleeson M, editor. Scott-Brown's otolaryngology. 7 th ed. London: Hodder Arnold 2008 * Hearing impairment and ear pathology in Nepal PLittle ABridges RGuragain DFriedman RPrasad RWeir 10.1017/S0022215100123278 J Laryngol Otol 107 1993 * Pattern of otological diseases in school-going children of the Sunsari district of Eastern Nepal SKThakur SKSingh BMahato ASingh DMahato 10.5580/IJORL.25808 The Internet Journal of Otorhinolaryngology 17 1 2015 * Chronic suppurative otitis media in urban private school children of Nepal PAdhikari SJoshi DBaral BKharel Braz J Otorhinolaryngol 2009 * Sep-Oct 10.1016/s1808-8694 75 * Prevalence of otitis media in school going children in Eastern Nepal MMaharjan SBhandari ISingh SCMishra Kathmandu Univ Med J 4 2006 * Prevalence of chronic suppurative otitis media and associated hearing impairment among school-aged children in Yemen SMuftah IMackenzie BFaragher BBrabin 10.5001/omj.2015.72 Oman Med J 30 2015 Sep * Prevalence of preventable ear disorders in over 15000 schoolchildren in northern India SKChadha ASayal VMalhotra AKAgarwal 10.1017/s0022215112002691 J Laryngol Otol 127 2013 * Chronic suppurative otitis media and its association with socio-economic factors among rural primary school children of Bangladesh MMShaheen ARaquib SMAhmad 10.1007/s12070-011-0150-9 Indian J Otolaryngol Head Neck Surg 64 2012 * Hearing loss and ear disorders in Malaysian school children SElango GNPurohit MHashim RHilmi * 10.1016/0165-5876(91)90098-v Int J Pediatr Otorhinolaryngol 22 1991 Jul * A study of the prevalence of and risk factors for ear diseases and hearing loss in primary school children in Hat Yai, Thailand SChayarpham JStuart VChongsuvivatwong SChinpairoj ALim J Med Assoc Thai 79 1996 Jul * Prevalence and risk factors of chronic otitis media in Korea: results of a nation-wide survey CSKim HWJung KYYoo 10.3109/0001648930913 Acta Otolaryngol 113 1993 * Otitis media in Indonesian urban and rural school children RAnggraeni WWHartanto BDjelantik AGhanie DSUtama EPSetiawan 10.1097/inf.0000000000000366 Pediatr Infect Dis J 33 2014 Oct * Prevalence of middle ear infections and associated risk factors in children under 5 years in Gasabo district of Kigali city, Rwanda KBMukara RJLilford DLTucci PWaiswa Int J Pediatr * 10.1155/2017/4280583 ID 4280583: 8 Article * Prevalence of paediatric chronic suppurative otitis media and hearing impairment in rural Malawi: A cross-sectional survey LHunt WMulwafu VKnott CBNdamala AWNaunje SDewhurst 10.1371/journal.pone.0188950 PLoS One 12 e0188950 2017 * Prevalence and etiological agents for chronic suppurative otitis media in a tertiary hospital in Tanzania ZSAbraham DNtunaguzi AAKahinga KBMapondella ERMassawe EJNkuwi 10.1186/s13104-019-4483-x BMC Res Notes 12 429 2019 * Otitis media and its sequelae in Kenyan schoolchildren EASimões FKiio PJCarosone-Link SNNdegwa JAyugi IMMacharia J Pediatric Infect Dis Soc 5 2016 Dec * Epidemiology of chronic suppurative otitis media among Saudi children-a comparative study of two decades SMZakzouk MFHajjaj Int J Pediatr Otorhinolaryngol 62 2002 * 10.1016/S0165-5876(01)00616-4 * Prevalence and impact of chronic otitis media in school age children in Brazil. First epidemiologic study concerning chronic otitis media in Latin America RNGodinho TmlGoncalves FBNunes CGBecker HmgBecker ResGuimaraes S0165-5876(01)00579-1 Int J Pediatr Otorhinolaryngol 61 2001 * Epidemiologic patterns in childhood hearing loss: a review JDavidson MLHyde PWAlberti 10.1016/0165-5876(89 Int J Pediatr Otorhinolaryngol 17 1989 Jul * The spectrum and management of otitis media in Australian indigenous and nonindigenous children: a national study HGunasekera SKnox PMorris HBritt PMcintyre JCCraig 10.1097/inf.0b013e3180621177 Pediatr Infect Dis J 26 2007 Aug * Otitis media and hearing loss among 12-16-year-old Inuit of Inukjuak HAyukawa SBruneau JFProulx JMacarthur JBaxter Int J Circumpolar Health 63 2004 * 10.3402/ijch.v63i0.17926 * The risk of hearing loss in a population with a high prevalence of chronic suppurative otitis media RGJensen AKoch PHomoe Int J Pediatr Otorhinolaryngol 77 2013 * 10.1016/j.ijporl.2013.06.025 * Chronic suppurative otitis media, middle ear pathology and corresponding hearing loss in a cohort of Greenlandic children MBAnvstorp PHomoe PBjerregaard RGJensen Int J Pediar Otorhinolaryngol 83 2016 * 10.1016/j.ijporl.2016.01.017 * Classification and management challenges of otitis media in a resource-poor country TSIbekwe OgbNwaorgu 10.4103/1119-3077.86764 Niger J Clin Pract 14 2011 Jul-Sep * Prevalence of chronic suppurative otitis media in schoolgoing children SMParmar ASood HSChakkal Indian journalof otolology 24 2018. 2018/24/4/223/ 254227 * Prevalence of chronic suppurative otitis media among schoolchildren residing in rural area of Belagavi, South India SABellad AKavi RSMudhol 10.1007/s12070-019-01627-9 Indian J Otolaryngol Head Neck Surg 71 2019 Nov * A cross sectional study of chronic suppurative otitis media and its associated factors among primary school children in rural and urban areas of Aligarh, India AParvez ZKhan SFHashmi MSKhan 10.18203/2394-6040.ijcmph20162561 Int J Community Med Public Health 3 2016 * Prevalence of chronic suppurative otitis media among the children living in two selected slums of Dhaka city NKamal AHJoarder AAChowdhury AWKhan Bangladesh Med Res Counc Bull 30 2004 Dec * Evaluation of contralateral ear in unilateral chronic otitis media: necessary or not? MThampi AGupta KSen SJain 10.1007/s12070-020-01824-x Indian J Otolaryngol Head Neck Surg 2020 * The contralateral ear in chronic otitis media: a series of 500 patients DaCosta SSRosito LpsDornelles CSperling N 10.1001/archoto.2007.38 Arch Otolaryngol Head Neck Surg 134 2008 Mar * Prevalence and associated risk factors of otitis media and its subtypes in South Indian population. Egyptian journal of ear nose throat and allied sciences MSKumari JMadhavi NBKrishna KRMeghanadh AJyothy 2016 17 * 10.1016/j.ejenta.2016.04.001 * Otitis media related hearing loss in Indonesian school children RAnggraeni PCarosone-Link BDjelantik EPSetiawan WWHartanto AGhanie 10.1016/j.ijporl.2019.06.019 Int J Pediatr Otorhinolaryngol 125 2019 Oct * Sensorineural hearing loss in chronic otitis media ZPapp SRezes IJókay ISziklai 10.1097/00129492-200303000-00003 Otol Neurotol 24 2003 Mar * Sensorineural hearing loss in chronic otitis media: analysis of an overlooked entity KCShetty SKJayaramaiah BKolathingal AlvaS 10.18203/issn.2454-5929.ijohns20193883 Int J Otorhinolaryngol Head Neck Surg 5 2019 Sep * Sensorineural hearing loss in chronic otitis media FCusimano VCocita D'amico A 10.1017/S0022215100108333 JLaryngolOtol 103 2007 * Sensorineural loss in chronic otitis media: Is it clinically significant? BALevine CShelton KIBerliner JLSheehy 10.1001/archotol.1989.01860310052021 Arch Otolaryngol Head Neck Surg 115 1989 * Sensorineural hearing loss in chronic otitis media CMacandie O'reillyBf 10.1046/j.1365-2273.1999.00237.x Clin Otolaryngol Allied Sci 24 2001 * Mucosal type of chronic suppurative otitis media and the long-term impact on hearing loss MSRajput MsaRajput AAArain SSZaidi AHatem SAkram 10.7759/cureus.10176 Cureus 12 e10176 2020 Sep * Analysis of sensorineural hearing loss in chronic suppurative otitis media HFeng YChen Lin Chuang Er Bi Yan Hou Ke Za Zhi 18 2004 Oct * Sensorineural hearing loss in patients with chronic suppurative otitis media: Is there a significant correlation? Electron Physician AAmali NHosseinzadeh SSamadi SNasiri JZebardast 10.19082/3823 2017 Feb 9 * Risk factors of sensorineural hearing loss in patients with unilateral safe chronic suppurative otitis media AeaSinger A-NogAwad RmaEl-Kader ARMohamed 10.1016/j.amjoto.2018.01.002 Am J Otolaryngol 39 2018 Mar-Apr * Long-term observation on hearing change in patients with chronic otitis media MSakagami AMaeda MNode MSone YMishiro 10.1016/s0385-8146(99)00065-6 Auris Nasus Larynx 27 2000 * Predictors for sensorineural hearing loss in patients with tubotympanic otitis, cholesteatoma, and tympanic membrane retractions SDJesic ADJotic BBBabic 10.1097/mao.0b013e318259b885 Otol Neurotol 33 2012 * A comparative evaluation of ear diseases in children of higher versus lower socioeconomic status SKChadha AKAgarwal AGulati AGarg 10.1017/S0022215105001520 J Laryngol Otol 120 2005 * Chronic suppurative otitis media in school children of Kathmandu Valley PAdhikari Int Arch Otorhinolaryngol 11 2007