Abstract
Purpose
This study was carried out to evaluate the diagnostic value of 226 and 1000 Hz probe-tone tympanometry in infants with effusion in the middle ear.
Methods
For this study, we recruited 52 infants with ages 42 days to 6 months as clinical subjects in a hearing-ability screening program. After a spiral computerized tomography (CT) scan of the patients, we tested their hearing using tympanometry of 2 probe-tone frequencies: 226 and 1000 Hz. The patients were divided into 2 groups according to the results of the CT scan: group 1 patients had normal middle ears without fluid, and group 2 patients had ears with fluid. We recorded the tympanograms and their percentage of every type and compared the tympanometric results with CT to get the concordance rate between tympanometry and CT diagnose while obtaining the normal values of 1000 Hz tympanometric measures.
Results
The 226 Hz probe-tone tympanograms of middle ears with fluid differed greatly from those without. At 226 Hz, their tympanograms were single-peaked tympanograms (51.06%), double-peaked tympanograms (44.68%), flat tympanograms (2.13%), and negative-pressure tympanograms (2.13%) for the group with normal middle ears, but single-peaked tympanograms (77.19%), double-peaked tympanograms (19.30%), and flat tympanograms (3.51%) for the group with middle ear effusion. The 1000 Hz probe-tone tympanograms included single-peaked or flat-type tympanograms in both the normal middle ear group and the group with middle ear effusion. The group with normal middle ears was identified by spiral CT, and its tympanograms mostly had a single peak (97.87%) during 1000 Hz tympanometry. Tympanograms of the middle ear effusion group mostly had a flat curve (98.25%). When the Liden/Jerger classification system was used to evaluate the tympanograms, normal tympanograms were single-peaked, and flat tympanograms indicated middle ear effusion. According to this standard, the concordance rate between the 1000 Hz tympanometry (98.08%) and CT diagnosis was higher than when 226 Hz tympanometry (25%) ( P < .05) was performed, and the value of κ was equal to 0.961 between 1000 Hz tympanometry and CT diagnosis.
Conclusions
In clinical practice, 1000 Hz tympanometry, not 226 Hz, is recommended to determine the presence of middle ear fluid in infants younger than 6 months.
1
Introduction
In recent years, newborn and infant hearing-ability screening programs have been implemented in a number of regions around the world. As a result of such programs, audiologic clinicians have had to deal with a very young patient population. Referred hearing-ability screenings have often resulted in higher false-positive rates, leading to added expenses, decreased program efficacy, and increased anxiety for parents . Middle ear fluid or effusion has been a major source of false-positive results during hearing-ability screening. It has also been commonly diagnosed in newborns and infants in neonatal intensive care units who are especially prone to this condition . A recent study pointed out that otitis media with effusion might contribute up to 67% of false-positive newborn hearing screenings . The presence of middle ear fluid severely diminished and even eliminated otoacoustic emissions (OAEs) because of mild middle ear conduction pathologies, and it led to refer result in more serious cases . Although significant efforts have been made to reduce the number of false-positive results by using more comprehensive screening protocols, the question of whether false-positive results arise from middle ear dysfunction stemming from otitis media with effusion or middle ear cavities containing mesenchyme and lacking full pneumatization at birth has not been adequately addressed .
Other studies have shown that subjects with respiratory tract infections frequently have a higher incidence of middle ear effusion or fluid in infants. Histopathological studies of the temporal bone have reported the presence of mesenchyme and liquid effusion in the middle ear cavity of infants. In a study done by Sa , 130 perinatal deaths were included, and the middle ears were examined histologically. Approximately 40% of these infants had aerated middle ears, and the remaining 60% had middle ear fluid. Three types of fluid were described: amniotic fluid, purulent inflammatory exudates, and a mucoid effusion. Mclellan et al reported finding a high rate of purulent otitis media, with 68% of 28 infants dying after delivery. Case reports about otitis media in infants have also been published sporadically .
Accordingly, it is of great importance to evaluate the state of the middle ear in infants so as to provide adequate rehabilitation for the population. Tympanometry is an objective and adequate test for detecting middle ear conditions. Several studies have demonstrated that tympanometry is important for evaluating middle ear function in infants.
Conventional tympanometry makes use of a 226 Hz probe tone as the criterion to distinguish conductive from sensorineural hearing loss in adults and older children . Unfortunately, conventional immittance evaluations of middle ear function with a 226 Hz probe tone have been demonstrated to be unreliable for accurate assessment of middle ear status in infants younger than 7 months . It is especially difficult to diagnose middle ear fluid in the newborn and young infants following referral from a hearing screening test. The effect of sound transmission through the neonatal ear canal to the middle ear and cochlea has not been described sufficiently and is therefore not well understood . The differences in sound transmission result in differently shaped tympanograms in infants compared to adults and older children . Developmental changes in the external and middle ear structures during the first months of life significantly affect the ear canal impedance and reflection coefficient responses . Middle ear compliance is lower, and resistance is higher, in infants compared to adults, and less power is transferred into the middle ear. Moreover, the resonant frequency of the tympanic membrane is much lower in children. Hence, the middle ear evolves from a mass-dominated to a stiffness-dominated system . As such, tympanometry in young children would be more effectively measured at probe-tone frequencies higher than 226 Hz .
Recent reports have demonstrated promising preliminary results from the use of a 1000 Hz probe tone to detect middle ear dysfunction in neonates . At this frequency, a single-peaked tympanogram was predominant as compared to that obtained from using a 226 Hz probe tone. Some studies showed a few case reports or samples of middle ear fluid conduction, but most only described normal tympanometric characteristics in infants using a 1000 Hz probe tone and then immediately concluded the more usefulness of 1000 Hz tympanometry in infants. From these studies, it remains difficult to determine the actual diagnostic value of 1000 Hz tympanometry in infants with middle ear fluid. As such reason, we conducted the present study to verify the value of 1000 Hz probe-tone tympanometry in infants identified with middle ear fluid by using computerized tomography (CT) test as standard because the conventional “golden standard” of myringotomy cannot clinically be used for such an age group. Institutional Human Subjects Review Board approval was obtained for the study.
2
Materials and methods
2.1
Subjects
The Institutional Human Subjects Review Board approved the study. Recordings were made from 104 neonatal ears from 52 neonates (30 males and 22 females) attending the maternal and children’s hospital in mid-China’s Hubei province. All neonates were full-term babies, and their ages at the time of testing varied between 42 days and 6 months (70 ± 28 days). Informed consent was obtained from all caregivers before any testing commenced. The testing protocol conducted on these ears included CT test and 226 and 1000 Hz frequency immittance measurements. During the CT test, subjects were administered with 10% chloral hydrate at a dosage of 0.5 mL kg −1 .
2.2
Instrumentation
2.2.1
Computerized tomography test
The CT scanner used was the GE Prospeed II (GE, America), and a cross-section helical scan was performed followed by a coronal multiplanar reformation. Scanning was done starting with a cross-section of the orbitomeatal line as the baseline and continuing with an ear canal bottom-up scan up to the superior edge of the rock cone. Coronal reorganization of the scans was done parallel to the back wall of the maxillary sinus as baseline, from the posterior border of the temporomandibular joint fossa to the anterior wall of the sigmoid sinus. The scanning was 2-mm slice thickness, the slice distance was 2 mm, the voltage was 120 kV, and the current was 230 mA, by 2i style.
Informed consent was obtained before conducting CT test, and all parents did not want to retest with the CT because of worry about radioactive injury.
2.2.2
Tympanometry
The Middle Ear Analyzer used was the Otoflex100 (Madsen, Denmark). The equipment was arranged to a 226 Hz tone at a constant level of 85 dB SPL and 1000 Hz at 75 dB SPL (signal level accuracy, ±1.5 dB SPL), with a pump speed of 100 decaPascals (daPa) per second, and positive-to-negative pressure sweep between +200 and −400 daPa.
2.3
Procedure
Tympanometry procedures involved sealing off the outer ear canal of each child by placing a probe tip fitted with an individually sized ear tip at the ear canal’s entrance. From the tympanometry test, we recorded the tympanogram, ear canal volume (Vec), tympanometric peak compliance (peak Y), tympanometric width (TW), and tympanometric peak pressure (TPP) in each ear. The percentage of each tympanogram in the 2 groups with CT was analyzed by a χ 2 test using the statistical software SPSS 11.5, and the value of κ was obtained. Before tympanometry, every ear was routinely inspected by electric auriscope.
2
Materials and methods
2.1
Subjects
The Institutional Human Subjects Review Board approved the study. Recordings were made from 104 neonatal ears from 52 neonates (30 males and 22 females) attending the maternal and children’s hospital in mid-China’s Hubei province. All neonates were full-term babies, and their ages at the time of testing varied between 42 days and 6 months (70 ± 28 days). Informed consent was obtained from all caregivers before any testing commenced. The testing protocol conducted on these ears included CT test and 226 and 1000 Hz frequency immittance measurements. During the CT test, subjects were administered with 10% chloral hydrate at a dosage of 0.5 mL kg −1 .
2.2
Instrumentation
2.2.1
Computerized tomography test
The CT scanner used was the GE Prospeed II (GE, America), and a cross-section helical scan was performed followed by a coronal multiplanar reformation. Scanning was done starting with a cross-section of the orbitomeatal line as the baseline and continuing with an ear canal bottom-up scan up to the superior edge of the rock cone. Coronal reorganization of the scans was done parallel to the back wall of the maxillary sinus as baseline, from the posterior border of the temporomandibular joint fossa to the anterior wall of the sigmoid sinus. The scanning was 2-mm slice thickness, the slice distance was 2 mm, the voltage was 120 kV, and the current was 230 mA, by 2i style.
Informed consent was obtained before conducting CT test, and all parents did not want to retest with the CT because of worry about radioactive injury.
2.2.2
Tympanometry
The Middle Ear Analyzer used was the Otoflex100 (Madsen, Denmark). The equipment was arranged to a 226 Hz tone at a constant level of 85 dB SPL and 1000 Hz at 75 dB SPL (signal level accuracy, ±1.5 dB SPL), with a pump speed of 100 decaPascals (daPa) per second, and positive-to-negative pressure sweep between +200 and −400 daPa.
2.3
Procedure
Tympanometry procedures involved sealing off the outer ear canal of each child by placing a probe tip fitted with an individually sized ear tip at the ear canal’s entrance. From the tympanometry test, we recorded the tympanogram, ear canal volume (Vec), tympanometric peak compliance (peak Y), tympanometric width (TW), and tympanometric peak pressure (TPP) in each ear. The percentage of each tympanogram in the 2 groups with CT was analyzed by a χ 2 test using the statistical software SPSS 11.5, and the value of κ was obtained. Before tympanometry, every ear was routinely inspected by electric auriscope.
3
Results
The tympanometry results were divided into 2 groups in accordance with the results from CT tests: the normal middle ear group and middle ear fluid group.
A summary of results organized according to the visual admittance classification system based on studies by Liden and Jerger for both 226 and 1000 Hz probe-tone frequencies is shown in Table 1 . To be discriminated easily, we used the majuscule alphabet “A,B,C,D,Du” as the represent code of 226 Hz tympanogram type and the minuscule alphabet “a,b,c,d,du” as the represent code of 1000 Hz tympanogram type. The distributions of 226 and 1000 Hz frequency tympanograms for the 2 groups are described in Table 2 , and the diagnosis concordance rate with CT is listed in parentheses.
