USE OF MULTIFREQUENCY MULTICOMPONENT TYMPANOMETRY IN THE AUDIOLOGICAL PROFILING OF FAMILIES WITH HISTORY OF OTOSCLEROSIS : AN EXPLORATORY STUDY
Roopa Nagarajan, (Professor and Course Chairperson), L-147
Vidya Ramkumar, (Lecturer), L-1093
Ramya Kapooria, Student (II M.Sc ASLP), L-1156
Supraba. J, Student (II M.Sc ASLP), L-1551
Department of Speech, Language and Hearing Sciences
Sri Ramachandra University
Porur, Chennai-600 116
Address for correspondence
Paper submitted for 43rd ISHA Con
Use of multifrequency multicomponent tympanometry in the audiological
profiling of families with history of otosclerosis : An exploratory study
The term otosclerosis refers to abnormal bone homeostasis of the otic capsule that leads to a bony fixation of the stapedial footplate in the oval window (Ali et al, 2007). Shambaugh, (1956) reported that age of onset is between 15-45 years and female to male ratio is approximately 2:1.Investigators in Tunisia (Ali et al, 2007) and Israel (Brownstein et al, 2006) have tried to establish the gene loci for otosclerosis. These involvedphenotyping several generations of family members using otological and audiological investigations.Studies have also been initiated in India (Tomek et al, 1998) to identify the gene loci specific to Indian population.
The clinical diagnosis of otosclerosis is made based on family history, otoscopic examination and audiological evaluation, though the confirmation is done after surgical exploration or postmortem. Audiologically, bilateral conductive hearing loss with onset in adulthood, presence of Carharts’s notch, absent stapedial reflexes, and type A tympanogram suggests the possibility of otosclerosis(Naumann, Porcellini, Fisch, 2005). The primary acoustic consequence in its early stages is the increase in stiffness reactance component of the total middle ear impedance. The diphasic ‘on-off’ reflex appears to be a sensitive indicator only in early stages of otosclerosis (Terkildsen et al, 1994).There have been suggestions that multifrequency tympanometry which allows the estimation of middle ear resonance frequency may be a useful tool in identifying otosclerosis (Ogut et al ,2008).
NEED
Investigators have identified different gene loci across different populations for otosclerosis (Chen et al, 2002., Bogaert et al, 2006., Brownstein et al, 2006) and the loci for otosclerosis is found to vary across races. These studies have included traditional audiological testing procedures such as pure tone audiometry, tympanometry and acoustic reflex for phenotyping. They have reported a wide range of audiological findings ranging from normal to severe hearing loss, conductive to mixed hearing loss, absent reflexes, and A, As or Ad type tympanogram. None of these studies have incorporated Multifrequency and Multicomponent (MFMC) tympanometry, even though it could be a useful tool in identifying stiffness related pathologies suchas otosclerosis. Hence, it is worthwhile to study the use of MFMC tympanometry in Indian families with history of otosclerosis.
AIM
To explore the usefulness of MFMC tympanometry as a part of the audiological test battery in profiling individuals with otosclerosis.
METHOD
The opportunity to explore the usefulness of MFMC tympanometry presented itself when a geneticist requested for audiological phenotyping of a family with history of otosclerosis. Forty five individuals (21F & 24M) in the age range 19 to 84 years (mean 42.53, SD 19.11) belonging to three generations of one family participated in the study. The number of individuals in the age group of 10-19, 20-29, 30-39, 40-49, 50-59, 70-79 and 80-89 years were 10,2,10,13,3 and 2 respectively. For each individual a detailed case history that included information about complaint or history of reduced hearing sensitivity, difficulty in understanding speech, ear pain, blockage or discharge, tinnitus and intolerance to loud sounds was obtained. Any complaint of giddiness or vomiting, head ache, diabetes, hypertension and family history of hearing loss was recorded.
Pure tone audiometry was done using GSI 61 with TDH-50P earphones and Radio Ear B71 bone vibrator.Immittance audiometry using 226Hz probe tone and MFMC tympanometry was carried out using GSI Tympstar Middle Ear Analyzer. Frequency sweep and pressure sweep method were used to measure the resonant frequency of middle earand was classified based on Holte, 1990. Multicomponent tympanogram was obtained using 678Hz probe tone and was interpreted with reference to the Vanhuyse model (Vanhuyse et al, 1975).
RESULTS
Six participants had undergone ear surgery for improving hearing subsequent to some loss in hearing in young adulthood. However, no written records were available to confirm that they had undergone stapedectomy. Otoscopic examination detected no abnormality in 44 of the 45 participants. One individual showed Schwartz sign. Seventeen participants had normal hearing bilaterally. Four had unilateral hearing loss and 24 participants had bilateral hearing loss. Among the 56 ears with hearing loss, sensorineural loss was predominant (38.8%), followed by mixed loss (11.1%) and conductive loss (7.7%). Hearing sensitivity varied from normal in 38 ears (42.2%) to severe to profound loss in 11 ears (12.2%). Low frequency probe tone tympanometry revealedtype A tympanogram in 85% of the ears and Ad type tympanogram in 13.3% ears. No participant demonstrated As type tympanogram or a negative on off reflex. Acoustic reflexes were absent in all participants having hearing loss.
Data from MFMC tympanometry showed that 57(63%) ears had normal resonant frequency, 32(35%) ears had high resonant frequency and 1(1 %) ear had low resonant frequency.Thirty two of ninety ears showed high resonant frequency with 1B1G pattern, suggesting that these ears may have some stiffness related condition.
One unexpected finding was the presence of high resonant frequencies in five ears with normal hearing in the 40-49 age group. All ears that underwent surgery had normal resonant frequency.
DISCUSSION
Results showed that three participants showed Carhart’s notch and one had Schwartz sign. One participant in the 20-29 age group demonstrated impedance signature. However there was much variation in the hearing thresholds, type and degree of loss. As a rule the younger members of the family had milder degrees of hearing loss when compared to the older members. This is not surprising as long standing otosclerosis often manifests as severe mixed loss and presbycusis could account for the degree of hearing loss.
Low frequency tympanometry was not very supportive of patterns seen in typical otosclerosis. Diphasic reflex and As tympanogram were not seen in any of the participants. It is well documented that 226 Hz probe is not very accurate in detecting stiffness related pathologies such as otosclerosis but higher probe tone frequencies are more diagnostic. In this study irrespective of type and degree of hearing loss, high middle ear resonant frequency was obtained in 35% of ears. There were two interesting findings; a) in the 6 ears that had been operated, the resonant frequency was normal; b) in 5 ears, high resonant frequency was noticed in the presence of normal hearing thresholds. These individuals were in the 40-49 years age range. It could be speculated that these ears could have some change in middle ear status tending towards increased stiffness that have as yet not manifested in the audiogram.
The results of this study suggest MFMC tympanometry could provide additional information especially if other audiological tests were inconclusive in individuals with suspected otosclerosis. The study also raises some intriguing questions;Can MFMC tympanometry help in detecting otosclerotic changes before they are manifested in routine audiological tests?;Would normalization of resonant frequency be an indicator of good surgical outcome?Should MFMC be always included in a battery of audiological tests in genetic/family based studies on otosclerosis?
CONCLUSION
This study was initiated to investigate the audiological phenotype in a family with history of otosclerosis and in part to provide support to a parallel study for identifying the genetic loci. Taking into consideration the results of the study, it would be useful to consider MFMC tympanometry as a part of routine audiological testing in order to provide more reliable diagnosis on stiffness related conditions pre surgically.