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Acoustic impedance studies on otitis media with effusion
International Journal oj Pediatric OtorhinolaryngoIogy, Elsevier Biomedical Press
4
(I 982) 89-94
Review Article
Acoustic impedance studies on otitis media with effusion Denzil N. Brooks Regional Audiology
Unit, Withington Hospital, Nell Lane. Manchester
N20 82R (U.K.)
(Received August 13th. 1981) (Accepted November 25th, 1981)
Introduction On 16th January 1867 Dr. August Lucae gave a lecture to the Berlin Medical Society in which he showed that information about the transmission characteristics of the middle ear could be obtained subjectively. Lucae used a device which he called an interference otoscope, based on the quarter wave Quinke tube. This was most probably the forerunner of the modern acoustic impedance instruments which, in the context of the present topic, perform the same function. The acoustic impedance instrument assesses the transmission or reflection characteristics of the middle ear as seen at the tympanic membrane (TM). In the normal auditory system the middle ear is a cavity containing air at or very close to atmospheric pressure. The tympanic membrane is free to vibrate with maximum efficiency and to transmit acoustic energy over a wide spectrum to the cochlea. If the air pressure in the external auditory canal is changed, the tympanic membrane is stiffened, decreasing the transmission efficiency and increasing the reflection of sound. This is the basis of the procedure known as tympanometry. The graphic representation of TM efficiency (or mobility or compliance) as a function of the pressure differential across the TM is known as a tympanogram. The normal tympanogram has a very characteristic shape. The peak of the curve where transmission is maximal and reflection is minimal occurs when the pressure in the external canal is exactly the same as that within the middle ear cavity. The overall height of the curve is a measure of the flexibility or compliance of the TM. Stiffened TM’s whether the stiffness arises directly from changes in the membrane itself or from a rigidity of the ossicular chain, result in tympanograms that are diminished in height. Flaccid TM’s or TM’s attached to hypermobile ossicular chains produce tympanograms that are taller and steeper than normal. In an ear where there is otitis media with effusion (OME) the transmission efficiency is greatly diminished. A high proportion of the incident energy is reflected regardless of the pressure in the external canal. The tympanogram is usually very 01655876/82/oooO-0/$02.75
0 1982 Elsevier Biomedical
Press
90
shallow, with the region of least stiffness displaced to the side of reduced pressure. In his original paper Lucae noted the action of the middle ear muscles, and showed that contractions could be detected by the increase in reflection at the TM. The presence of a stapedius muscle contraction very strongly contra-indicates the presence of OME, and can be detected with great sensitivity by a modern acoustic impedance instrument. The combination of tympanometry and middle ear muscle monitoring has proven to be very effective in identifying OME. At least 10 studies (TableI) have been performed in which impedance measurements have been employed to identify OME, the cross correlation being with otoscopy. The sensitivity, that is, the correct identification of ears with OME, ranged from 69 to lOO%, with an average of 91%. In other words, better than 9 out of 10 ears with OME would be identified by impedance measurement. The specificity-the correct identification of disease-free ears-ranged from 82 to 99%, with an average of 94%-equivalent to an over-referral rate of 6%. These data cannot, however, be accepted uncritically. Otoscopy is not an exact method of determining the presence or absence of OME. Paradise [ 161 carried out an investigation into the diagnostic skills of a number of individuals who were involved in pediatric otoscopy on a regular basis. Even though they were aware that their skill was under test, 15-20% of effusions were missed. Similar accuracy was reported by Reichert and his co-workers [ 191, 18% of ears being misdiagnosed when comparing otoscopy with findings at myringotomy. In the study of Roeser et al. [26], two very experienced otologists disagreed in 11% of cases reviewed as to whether otoscopic examination indicated a need for urgent treatment. An alternative method of validating impedance measurements is to compare predictions with findings at myringotomy. In 8 published studies (Table II) the sensitivity of impedance measurement ranged from 65 to 99% with a weighted average of 89%. Specificity ranged from 45 to 100% with a weighted average of 77%.
TABLE
I
Authors
Year
n
Sensitivity
Specificity
I. 2. 3. 4. 5. 6. 7. 8. 9. IO.
1974 1976 1976 I976 1976 1977 1977 1978 I979 1979
730 253 1013 53 120 97 191 1020 822 154
92 77- 88 97 96 96 79-100 69- 80 87 95 95
98 89-92 90
McCandless and Thomas Paradise, Smith and Bluestone Roberts Schwartz and Redfield Weaver et al. Findlay, Stool and Svitko Roeser et al. Urban Stewart et al. su
Range Weighted
average
82-88 89-94 _ 99 88
69- 100
82-99
91
94
TABLE
II
Authors
Year
n
Sensitivity
Specificity
I. 2. 3. 4. 5. 6. 7. 8.
1968 1974 1975 1976 1977 I978 1978 1980
233 II9 120 219 214 142 76 257
95 X4-X5 96 YX x5 65 90 X7-99
77 x0- xx Y3 6’) XX 72 100 45- XI
65-90
45 - 100
X9
77
Brooks Beery et al. Beery et al. Grimaldi Williams and Haughton Orchik, Dunn and McNutt Orchik, Morff and Dunn Fria, Cantekin and Probst
Range Weighted
average
Impedance measurement has, then, a high sensitivity in detecting OME when compared with either otoscopy or myringotomy. Few significant problems will be overlooked. The specificity compared well with otoscopy but less well with myringotomy. The probable explanation for this discrepancy is that both otoscopy and impedance tend to classify as outside normal limits a number of ears that do not have frank OME-a not surprising finding. On the basis of this information impedance testing appears to be highly suitable for identifying OME in a pediatric population, being accurate but not over-sensitive, while at the same time being simple, acceptable and harmless. However, before recommending initiation of widespread screening for OME, it is important to decide if there is either need for, or merit in identifying every child with this condition. Clinical experience suggests that many, possibly the majority of children have bouts of middle ear dysfunction but recover without treatment and without apparent ill-effects. A minority only appear to have persistent effusion and consequent problems.
Should we, and can we differentiate between those whose problem is transient and those who will have more lasting difficulties? Some findings of a study into middle ear function carried out on a group of 80 children over a period of 10 years [21] may help in answering this question. At the commencement of the study the children were about 5 years of age and just starting full-time education. During their first year at school the middle ear function was tested at roughly two weekly intervals using either a Madsen 2070 or a Peters AP61 impedance bridge, these being calibrated regularly during the course of the study. During the second school year the intervals were increased for most of the children, although those with effusion were seen at approximately the same intervals. In subsequent years, the interval between tests was increased as the incidence of OME decreased.
92
About one half of the children did not at any time during the course of the investigation produce tympanograms suggestive of middle ear dysfunction. The compliance, middle ear pressure and muscle reflexes were within normal limits throughout. About one third of the children gave evidence of transient OME on either one or two occasions. The first bout was usually six weeks or so after commencement of schooling-in October or November. The second time period when OME was most frequently observed was in the March-April period. With this group of children it is notable that the middle ear function was normal when they were first seen, and indeed remained so for several weeks. The episodes of effusion went unobserved by either parents, teachers or doctors-although some of the children were stated to be suffering from colds. In all these children recovery from the effusion appeared to be total and without any suggestion of adverse consequence either physically or educationally. The remaining sixth of the children had either episodic or persistent OME. Closer analysis of the records led to a sub-division into two categories. The majority entered school with normal middle ear function as shown on the impedance test. As with children in the second group, effusion was first noted some 6 to 8 weeks later but whereas the children in Group 2 recovered and reverted to normal, these children then went on to have further bouts of effusion, or did not appear to recover from the first bout. Middle ear function remained abnormal for 18 months or two years and then, apparently spontaneously, recovered. It is again worthy of note that none of these children received specialist treatment during the period of middle ear dysfunction. One or two were examined and listed for tonsillectomy and adenoidectomy, but (because of the long waiting lists) the operations were not performed until, according to the impedance findings, the middle ears had recovered. A minority of the third group representing perhaps 3-5% of the total group of eighty, had persistent OME which, later scrutiny of the records revealed, was present at the first test performed only a few days after the child’s entry into school. It is not possible to be dogmatic with such small numbers, but there was some suggestion that these children did not perform at the academic level expected of them, and one wonders if this was a consequence of the persistent though slight hearing loss associated with OME.
Should we and can we differentiate between children whose problem is transient and those who will have more lasting difficulties? The answer seems to be a qualified affirmative. By employing impedance tests repeated over carefully chosen time intervals it is possible to accurately differentiate between the transient and persistent effusion. The transient OME appears to resolve without external treatment, whereas the persistent, by definition, does not. Assuming agreement on the need for detection of persistent OME, and further assuming that impedance is seen as an acceptable method of identifying those with this condition, the question then arises as to when the tests should be performed, that is, at what age. It is most practicable when the children are easy of access after
93
commencing schooling. This will be at age 5 in England, but may be at a later age in other countries. However, the longitudinal study of the 80 children revealed that those with persistent OME gave evidence of having this as an established condition when they commenced school at age 5. It seems that to try and detect the condition in the acute or prechronic stage, the testing will have to be performed at an earlier age. The studies of Howie and his colleagues [ 10,l l] indicate that although most infants have episodes of OME in the first year or two of life, only a small number have multiple episodes. These children Howie terms ‘otitis prone’. Ideally then the identification process should be as early as possible. Although it is certainly possible to perform tympanometry at a very early age [4,12] there is some doubt about its validity before 7 or 9 months of age [l]. A reasonable compromise seems to be to suggest that testing might be performed at around two years of age-before the middle ear dysfunction is too well established but after the period of testing uncertainty and difficulty due to eruption of teeth. Poulson and Tos [ 181 have performed repetitive impedance studies on a group of 2 year old children at three monthly intervals. These showed that there was a very considerable fluctuation between normal and abnormal middle ear conditions, partly dependent on the season of the year. The variability was such that Tos [25] concluded that ‘impedance screening as a prophylactic means to diagnose a middle ear disease would be meaningless’. He believed it would ‘lead to excessive treatment of secretory otitis media’. This conclusion might be somewhat pessimistic. In the study of Tos we find that 5 1 of the 222 children had flat tympanograms at the first test. Twenty-seven of these reverted to more normal patterns by the second test; seven more changed from the flat type by the third test, and at the final test only 7 remained with the typical OME tympanogram. In total only 1.6% of the children had clear indication of OME over the 4 tests and 3.4% at 3 out of 4 tests. These percentages are of the same magnitude as for children with persistent OME in the longitudinal study of Brooks [6]. Obviously it is not certain that these would be the same children that persisted with OME over many years, but it does seem not unlikely. If by the age of 3 identification can be made of this small number-say 2-5% of children with potentially persistent OME, the worst of the consequences might be mitigated. Tos [25] states that ‘analysis of the causative factors showed that catarrhalia is by far the most common cause of secretory otitis, and we do not know how to prevent a child from becoming catarrhal’. But there are other methods by which the child can be assisted. If it is established beyond doubt that persistent OME leads on to educational retardation, then one approach might be through programmed special education. Furthermore, it may be that identifying the subject with potential middle ear dysfunction when the disorder is in the acute or sub-acute stage rather than when it has become chronic might render treatment more effective. Certainly one would agree with Tos [25] in his concluding comments on this difficult problem. ‘Only systematic long-term studies, also based on impedance screenings, of children from the first year of life until school age may perhaps bring us nearer to a solution of this problem.’
94
References in infants, Aud. Hear. Ed., 4 (3) (1978) 17. I Balkany, T.J.and Zamoch, J.M., Impedance tympanometry 2 Beery, Q.C., Bluestone, C.D., Cantekin, E.I. and Gould, E.C., A comparative study of tympanometric patterns in relation to middle ear effusions. Paper presented at the American Speech and Heating Convention, Las Vegas, Novr. 6, 1974. 3 Beery, Q.C., Andrus, W.S., Bluestone, C.D. and Cantekin, E., Tympanometric pattern classification in relation to middle ear effusions, Ann. Otol., 84 (1975) 56-64. 4 Bennett, M.J., Acoustic impedance bridge measurements with the neonate, Brit. J. Audiol., 9 (I 975) 117-124. 5 Brooks, D.N., An objective method of detecting fluid in the middle ear, Int. Audiol., 7 (1968) 280-286. Brooks, D.N., School screening for middle ear effusions, Ann. Otol.. Suppl. 25 (I 976) 223-228. Findlay, R.C., Stool, SE. and Svitko, M.S., Tympanometric and otoscopic evaluations of the school-age deaf population: a longitudinal study. Fria, T.J., Cantekin, E.U. and Probst, G., Validation of an automatic otoadmittance middle ear analyzer, Ann. Otol., 89 (I 980) 253-256. Grimaldi, P.M.G.B., The value of impedance testing in diagnosis of middle ear effusion, JLO, 90 (1976) 141-152. IO Howie, V.M., Natural history of otitis media, Ann., Otol., Suppl. I9 (1975) 67-72. 11 Howie, V.M., Ploussard, J.H. and Sloyer, J., The “otitis-prone” condition, Amer. J. Dis. Child., 129 (1975) 676-678. 12 Keith, R.W., Middle ear function in neanates, Arch. Otolaryng., IO1 (1975) 376-379. G.A. and Thomas, G.K., Impedance audiometry as a screening procedure for middle ear 13 McCandless, disease, Trans. Amer. Acad. Ophthal. Otolaryng., 78 (1974) 2-6. 14 Orchik, D.J., Dunn, J.W. and McNutt, L., Tympanometry as a predictor of middle ear effusion, Arch. Otol., I04 (1978) 4-6. audiometry in serous otitis media, Arch. 15 Orchik, D.J., Morff, R. and Dunn, J.W., Impedance Otolaryng., I04 (1978) 409-412. view of middle ear effusions. More questions than answers. Ann. Otol., 16 Paradise, J.L., Paediatricians Suppl. 25 (I 976) 20-24. detection of middle ear effusion in 17 Paradise, J.L., Smith, C.G. and Bluestone, C.D., Tympanometric infants and children, Pediatrics, 58 (I 976) 198-2 IO. 18 Poulsen, G. and Tos, M., Repetitive tympanometric screening of two-year-old children, Stand. Audiol., 9 (I 980) 2 l-28. 19 Reichert, T.J., Cantekin, E.I., Riding, K.H., Cohn, B.L. and Bluestone, C., Diagnosis of middle ear effusions in young infants by otoscopy and tympanometry. In Harford. Bess, Bluestone and Klein (Eds.), Impedance Screening for Middle Ear Disease in Children. 20 Roberts, M.E., Grune and Stratton. Comparative study of pure tone, impedance and otoscopic hearing screening methods, Arch. Otolaryng., 102 (1976) 690-694. 21 Roeser, R.J., Soh, J., Dunckel, D.C. and Adams, R., Comparison of tympanometry and otoscopy in establishing pass/fail referral criteria, J. Amer. audiol. Sot., 3 (1977) 20-25. 22 Schwartz, D.M. and Redfield, N.P., Evaluation of automatic screening tympanometry in the identification of middle ear pathology, J. Amer. audiol. Sot., 1 (1976) 276-279. 23 Stewart, A., Kirkland, C. et al., Otological and audiological abnormalities in pre-school children. A report from the Dunedin multidisciplinary Child Development Study-New Zealand, 1979. 24 Su, A.P., Screening for glue ears-A pilot study. Personal Communication, 1979. 25 Tos, M., Spontaneous improvement of secretory otitis and impedance screening, Arch. Otolaryng.. 106 (1980) 345-349. 26 Urban, B., Impedance in a school screening programme. In Harford, Bess, Bluestone, Klein (Eds.) Impedance Screening for Middle Ear disease in Children. 27 Weaver, R.M., Arbon, R.A., Watkins, P.L. and Olsen, R.G., Comparisons among two different electro-acoustic impedance measures and otoscopy by an ENT specialist in identifying middle ear anomalies in mental retardates, J. Aud. Res., I6 (1976) 239-246. 28 Williams, R.G. and Hat&ton, P.M., Tympanometric diagnosis of middle ear effusions, JLO. 91 (I 977) 959-962.
4
(I 982) 89-94
Review Article
Acoustic impedance studies on otitis media with effusion Denzil N. Brooks Regional Audiology
Unit, Withington Hospital, Nell Lane. Manchester
N20 82R (U.K.)
(Received August 13th. 1981) (Accepted November 25th, 1981)
Introduction On 16th January 1867 Dr. August Lucae gave a lecture to the Berlin Medical Society in which he showed that information about the transmission characteristics of the middle ear could be obtained subjectively. Lucae used a device which he called an interference otoscope, based on the quarter wave Quinke tube. This was most probably the forerunner of the modern acoustic impedance instruments which, in the context of the present topic, perform the same function. The acoustic impedance instrument assesses the transmission or reflection characteristics of the middle ear as seen at the tympanic membrane (TM). In the normal auditory system the middle ear is a cavity containing air at or very close to atmospheric pressure. The tympanic membrane is free to vibrate with maximum efficiency and to transmit acoustic energy over a wide spectrum to the cochlea. If the air pressure in the external auditory canal is changed, the tympanic membrane is stiffened, decreasing the transmission efficiency and increasing the reflection of sound. This is the basis of the procedure known as tympanometry. The graphic representation of TM efficiency (or mobility or compliance) as a function of the pressure differential across the TM is known as a tympanogram. The normal tympanogram has a very characteristic shape. The peak of the curve where transmission is maximal and reflection is minimal occurs when the pressure in the external canal is exactly the same as that within the middle ear cavity. The overall height of the curve is a measure of the flexibility or compliance of the TM. Stiffened TM’s whether the stiffness arises directly from changes in the membrane itself or from a rigidity of the ossicular chain, result in tympanograms that are diminished in height. Flaccid TM’s or TM’s attached to hypermobile ossicular chains produce tympanograms that are taller and steeper than normal. In an ear where there is otitis media with effusion (OME) the transmission efficiency is greatly diminished. A high proportion of the incident energy is reflected regardless of the pressure in the external canal. The tympanogram is usually very 01655876/82/oooO-0/$02.75
0 1982 Elsevier Biomedical
Press
90
shallow, with the region of least stiffness displaced to the side of reduced pressure. In his original paper Lucae noted the action of the middle ear muscles, and showed that contractions could be detected by the increase in reflection at the TM. The presence of a stapedius muscle contraction very strongly contra-indicates the presence of OME, and can be detected with great sensitivity by a modern acoustic impedance instrument. The combination of tympanometry and middle ear muscle monitoring has proven to be very effective in identifying OME. At least 10 studies (TableI) have been performed in which impedance measurements have been employed to identify OME, the cross correlation being with otoscopy. The sensitivity, that is, the correct identification of ears with OME, ranged from 69 to lOO%, with an average of 91%. In other words, better than 9 out of 10 ears with OME would be identified by impedance measurement. The specificity-the correct identification of disease-free ears-ranged from 82 to 99%, with an average of 94%-equivalent to an over-referral rate of 6%. These data cannot, however, be accepted uncritically. Otoscopy is not an exact method of determining the presence or absence of OME. Paradise [ 161 carried out an investigation into the diagnostic skills of a number of individuals who were involved in pediatric otoscopy on a regular basis. Even though they were aware that their skill was under test, 15-20% of effusions were missed. Similar accuracy was reported by Reichert and his co-workers [ 191, 18% of ears being misdiagnosed when comparing otoscopy with findings at myringotomy. In the study of Roeser et al. [26], two very experienced otologists disagreed in 11% of cases reviewed as to whether otoscopic examination indicated a need for urgent treatment. An alternative method of validating impedance measurements is to compare predictions with findings at myringotomy. In 8 published studies (Table II) the sensitivity of impedance measurement ranged from 65 to 99% with a weighted average of 89%. Specificity ranged from 45 to 100% with a weighted average of 77%.
TABLE
I
Authors
Year
n
Sensitivity
Specificity
I. 2. 3. 4. 5. 6. 7. 8. 9. IO.
1974 1976 1976 I976 1976 1977 1977 1978 I979 1979
730 253 1013 53 120 97 191 1020 822 154
92 77- 88 97 96 96 79-100 69- 80 87 95 95
98 89-92 90
McCandless and Thomas Paradise, Smith and Bluestone Roberts Schwartz and Redfield Weaver et al. Findlay, Stool and Svitko Roeser et al. Urban Stewart et al. su
Range Weighted
average
82-88 89-94 _ 99 88
69- 100
82-99
91
94
TABLE
II
Authors
Year
n
Sensitivity
Specificity
I. 2. 3. 4. 5. 6. 7. 8.
1968 1974 1975 1976 1977 I978 1978 1980
233 II9 120 219 214 142 76 257
95 X4-X5 96 YX x5 65 90 X7-99
77 x0- xx Y3 6’) XX 72 100 45- XI
65-90
45 - 100
X9
77
Brooks Beery et al. Beery et al. Grimaldi Williams and Haughton Orchik, Dunn and McNutt Orchik, Morff and Dunn Fria, Cantekin and Probst
Range Weighted
average
Impedance measurement has, then, a high sensitivity in detecting OME when compared with either otoscopy or myringotomy. Few significant problems will be overlooked. The specificity compared well with otoscopy but less well with myringotomy. The probable explanation for this discrepancy is that both otoscopy and impedance tend to classify as outside normal limits a number of ears that do not have frank OME-a not surprising finding. On the basis of this information impedance testing appears to be highly suitable for identifying OME in a pediatric population, being accurate but not over-sensitive, while at the same time being simple, acceptable and harmless. However, before recommending initiation of widespread screening for OME, it is important to decide if there is either need for, or merit in identifying every child with this condition. Clinical experience suggests that many, possibly the majority of children have bouts of middle ear dysfunction but recover without treatment and without apparent ill-effects. A minority only appear to have persistent effusion and consequent problems.
Should we, and can we differentiate between those whose problem is transient and those who will have more lasting difficulties? Some findings of a study into middle ear function carried out on a group of 80 children over a period of 10 years [21] may help in answering this question. At the commencement of the study the children were about 5 years of age and just starting full-time education. During their first year at school the middle ear function was tested at roughly two weekly intervals using either a Madsen 2070 or a Peters AP61 impedance bridge, these being calibrated regularly during the course of the study. During the second school year the intervals were increased for most of the children, although those with effusion were seen at approximately the same intervals. In subsequent years, the interval between tests was increased as the incidence of OME decreased.
92
About one half of the children did not at any time during the course of the investigation produce tympanograms suggestive of middle ear dysfunction. The compliance, middle ear pressure and muscle reflexes were within normal limits throughout. About one third of the children gave evidence of transient OME on either one or two occasions. The first bout was usually six weeks or so after commencement of schooling-in October or November. The second time period when OME was most frequently observed was in the March-April period. With this group of children it is notable that the middle ear function was normal when they were first seen, and indeed remained so for several weeks. The episodes of effusion went unobserved by either parents, teachers or doctors-although some of the children were stated to be suffering from colds. In all these children recovery from the effusion appeared to be total and without any suggestion of adverse consequence either physically or educationally. The remaining sixth of the children had either episodic or persistent OME. Closer analysis of the records led to a sub-division into two categories. The majority entered school with normal middle ear function as shown on the impedance test. As with children in the second group, effusion was first noted some 6 to 8 weeks later but whereas the children in Group 2 recovered and reverted to normal, these children then went on to have further bouts of effusion, or did not appear to recover from the first bout. Middle ear function remained abnormal for 18 months or two years and then, apparently spontaneously, recovered. It is again worthy of note that none of these children received specialist treatment during the period of middle ear dysfunction. One or two were examined and listed for tonsillectomy and adenoidectomy, but (because of the long waiting lists) the operations were not performed until, according to the impedance findings, the middle ears had recovered. A minority of the third group representing perhaps 3-5% of the total group of eighty, had persistent OME which, later scrutiny of the records revealed, was present at the first test performed only a few days after the child’s entry into school. It is not possible to be dogmatic with such small numbers, but there was some suggestion that these children did not perform at the academic level expected of them, and one wonders if this was a consequence of the persistent though slight hearing loss associated with OME.
Should we and can we differentiate between children whose problem is transient and those who will have more lasting difficulties? The answer seems to be a qualified affirmative. By employing impedance tests repeated over carefully chosen time intervals it is possible to accurately differentiate between the transient and persistent effusion. The transient OME appears to resolve without external treatment, whereas the persistent, by definition, does not. Assuming agreement on the need for detection of persistent OME, and further assuming that impedance is seen as an acceptable method of identifying those with this condition, the question then arises as to when the tests should be performed, that is, at what age. It is most practicable when the children are easy of access after
93
commencing schooling. This will be at age 5 in England, but may be at a later age in other countries. However, the longitudinal study of the 80 children revealed that those with persistent OME gave evidence of having this as an established condition when they commenced school at age 5. It seems that to try and detect the condition in the acute or prechronic stage, the testing will have to be performed at an earlier age. The studies of Howie and his colleagues [ 10,l l] indicate that although most infants have episodes of OME in the first year or two of life, only a small number have multiple episodes. These children Howie terms ‘otitis prone’. Ideally then the identification process should be as early as possible. Although it is certainly possible to perform tympanometry at a very early age [4,12] there is some doubt about its validity before 7 or 9 months of age [l]. A reasonable compromise seems to be to suggest that testing might be performed at around two years of age-before the middle ear dysfunction is too well established but after the period of testing uncertainty and difficulty due to eruption of teeth. Poulson and Tos [ 181 have performed repetitive impedance studies on a group of 2 year old children at three monthly intervals. These showed that there was a very considerable fluctuation between normal and abnormal middle ear conditions, partly dependent on the season of the year. The variability was such that Tos [25] concluded that ‘impedance screening as a prophylactic means to diagnose a middle ear disease would be meaningless’. He believed it would ‘lead to excessive treatment of secretory otitis media’. This conclusion might be somewhat pessimistic. In the study of Tos we find that 5 1 of the 222 children had flat tympanograms at the first test. Twenty-seven of these reverted to more normal patterns by the second test; seven more changed from the flat type by the third test, and at the final test only 7 remained with the typical OME tympanogram. In total only 1.6% of the children had clear indication of OME over the 4 tests and 3.4% at 3 out of 4 tests. These percentages are of the same magnitude as for children with persistent OME in the longitudinal study of Brooks [6]. Obviously it is not certain that these would be the same children that persisted with OME over many years, but it does seem not unlikely. If by the age of 3 identification can be made of this small number-say 2-5% of children with potentially persistent OME, the worst of the consequences might be mitigated. Tos [25] states that ‘analysis of the causative factors showed that catarrhalia is by far the most common cause of secretory otitis, and we do not know how to prevent a child from becoming catarrhal’. But there are other methods by which the child can be assisted. If it is established beyond doubt that persistent OME leads on to educational retardation, then one approach might be through programmed special education. Furthermore, it may be that identifying the subject with potential middle ear dysfunction when the disorder is in the acute or sub-acute stage rather than when it has become chronic might render treatment more effective. Certainly one would agree with Tos [25] in his concluding comments on this difficult problem. ‘Only systematic long-term studies, also based on impedance screenings, of children from the first year of life until school age may perhaps bring us nearer to a solution of this problem.’
94
References in infants, Aud. Hear. Ed., 4 (3) (1978) 17. I Balkany, T.J.and Zamoch, J.M., Impedance tympanometry 2 Beery, Q.C., Bluestone, C.D., Cantekin, E.I. and Gould, E.C., A comparative study of tympanometric patterns in relation to middle ear effusions. Paper presented at the American Speech and Heating Convention, Las Vegas, Novr. 6, 1974. 3 Beery, Q.C., Andrus, W.S., Bluestone, C.D. and Cantekin, E., Tympanometric pattern classification in relation to middle ear effusions, Ann. Otol., 84 (1975) 56-64. 4 Bennett, M.J., Acoustic impedance bridge measurements with the neonate, Brit. J. Audiol., 9 (I 975) 117-124. 5 Brooks, D.N., An objective method of detecting fluid in the middle ear, Int. Audiol., 7 (1968) 280-286. Brooks, D.N., School screening for middle ear effusions, Ann. Otol.. Suppl. 25 (I 976) 223-228. Findlay, R.C., Stool, SE. and Svitko, M.S., Tympanometric and otoscopic evaluations of the school-age deaf population: a longitudinal study. Fria, T.J., Cantekin, E.U. and Probst, G., Validation of an automatic otoadmittance middle ear analyzer, Ann. Otol., 89 (I 980) 253-256. Grimaldi, P.M.G.B., The value of impedance testing in diagnosis of middle ear effusion, JLO, 90 (1976) 141-152. IO Howie, V.M., Natural history of otitis media, Ann., Otol., Suppl. I9 (1975) 67-72. 11 Howie, V.M., Ploussard, J.H. and Sloyer, J., The “otitis-prone” condition, Amer. J. Dis. Child., 129 (1975) 676-678. 12 Keith, R.W., Middle ear function in neanates, Arch. Otolaryng., IO1 (1975) 376-379. G.A. and Thomas, G.K., Impedance audiometry as a screening procedure for middle ear 13 McCandless, disease, Trans. Amer. Acad. Ophthal. Otolaryng., 78 (1974) 2-6. 14 Orchik, D.J., Dunn, J.W. and McNutt, L., Tympanometry as a predictor of middle ear effusion, Arch. Otol., I04 (1978) 4-6. audiometry in serous otitis media, Arch. 15 Orchik, D.J., Morff, R. and Dunn, J.W., Impedance Otolaryng., I04 (1978) 409-412. view of middle ear effusions. More questions than answers. Ann. Otol., 16 Paradise, J.L., Paediatricians Suppl. 25 (I 976) 20-24. detection of middle ear effusion in 17 Paradise, J.L., Smith, C.G. and Bluestone, C.D., Tympanometric infants and children, Pediatrics, 58 (I 976) 198-2 IO. 18 Poulsen, G. and Tos, M., Repetitive tympanometric screening of two-year-old children, Stand. Audiol., 9 (I 980) 2 l-28. 19 Reichert, T.J., Cantekin, E.I., Riding, K.H., Cohn, B.L. and Bluestone, C., Diagnosis of middle ear effusions in young infants by otoscopy and tympanometry. In Harford. Bess, Bluestone and Klein (Eds.), Impedance Screening for Middle Ear Disease in Children. 20 Roberts, M.E., Grune and Stratton. Comparative study of pure tone, impedance and otoscopic hearing screening methods, Arch. Otolaryng., 102 (1976) 690-694. 21 Roeser, R.J., Soh, J., Dunckel, D.C. and Adams, R., Comparison of tympanometry and otoscopy in establishing pass/fail referral criteria, J. Amer. audiol. Sot., 3 (1977) 20-25. 22 Schwartz, D.M. and Redfield, N.P., Evaluation of automatic screening tympanometry in the identification of middle ear pathology, J. Amer. audiol. Sot., 1 (1976) 276-279. 23 Stewart, A., Kirkland, C. et al., Otological and audiological abnormalities in pre-school children. A report from the Dunedin multidisciplinary Child Development Study-New Zealand, 1979. 24 Su, A.P., Screening for glue ears-A pilot study. Personal Communication, 1979. 25 Tos, M., Spontaneous improvement of secretory otitis and impedance screening, Arch. Otolaryng.. 106 (1980) 345-349. 26 Urban, B., Impedance in a school screening programme. In Harford, Bess, Bluestone, Klein (Eds.) Impedance Screening for Middle Ear disease in Children. 27 Weaver, R.M., Arbon, R.A., Watkins, P.L. and Olsen, R.G., Comparisons among two different electro-acoustic impedance measures and otoscopy by an ENT specialist in identifying middle ear anomalies in mental retardates, J. Aud. Res., I6 (1976) 239-246. 28 Williams, R.G. and Hat&ton, P.M., Tympanometric diagnosis of middle ear effusions, JLO. 91 (I 977) 959-962.