Navid Shahnaz

Prof. Dr. Navid Shahnaz

The University of British Columbia, Vancouver, British Columbia, Canada
orcid

Research Focus & Metrics

Academic Career Length

21Years (2006-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 April 2009 in Ear & Hearing
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
KBKarin Bork
Karin Bork
LPLinda Polka
Linda Polka
NLNeil Longridge
Neil Longridge
DBDesmond Bell
Desmond Bell
BWBrian D. Westerberg
Brian D. Westerberg
The major goal of this study was to examine differences in the middle ear mechano-acoustical properties of normal ears and ears with surgically confirmed otosclerosis using conventional and multifrequency tympanometry (MFT) as well as energy reflectance (ER). Second, we sought to compare ER, standard tympanometry, and MFT in their ability to distinguish healthy and otosclerotic ears examining both overall test performance (sensitivity and specificity) and receiver- operating characteristic analyses. Sixty-two normal-hearing adults and 28 patients diagnosed with otosclerosis served as subjects. Tympanometric data were gathered on a clinical immittance machine, the Virtual 310 equipped with a high-frequency option. Two of the parameters, static admittance and tympanometric width, were measured automatically at a standard 226 Hz frequency. The remaining two parameters, resonant frequency and frequency corresponding to admittance phase angle of 45 degree (F45 degrees ), were derived from MFT, multicomponent tympanometry, using a mathematical approach similar to the method used in GSI Tympstar Version 2. ER data were gathered using Mimosa Acoustics (RMS-system v4.0.4.4) equipment. Analyses of receiver-operating characteristic plots confirmed the advantage of MFT measures of resonant frequency and F45 degrees over the standard low-frequency measures of static admittance and tympanometric width with respect to distinguishing otosclerotic ears from normal ears. The F45 degrees measure was also found to be the best single index for making this distinction among tympanometric parameters. ER less than 1 kHz was significantly higher in otosclerotic ears than normal ears. This indicates that most of the incident energy below 1 kHz is reflected back into the ear canal in otosclerotic ears. ER patterns exceeding the 90th percentile of the normal ears across all frequencies correctly identify 82% of the otosclerotic ears while maintaining a low false alarm rate (17.2%); thus, this measure outperforms the other individual tympanometric parameters. Combination of ER and F45 degrees were able to distinguish all otosclerotic ears. Correlations and the individual patterns of test performance revealed that information provided by ER is supplemental to the information provided by conventional and MFT with respect to distinguishing otosclerotic ears from normal ears. The present findings show that the overall changes of ER across frequencies can distinguish otosclerotic ears from normal ears and from other sources of conductive hearing loss. Incorporating ER in general practice will improve the identification of otosclerotic ears when conventional tympanometry and MFT may fail to do so. To further improve the false alarm rate, ER should be interpreted in conjunction with other audiologic test batteries because it is unlikely that signs of a conductive component, including abnormal middle ear muscle reflex and ER responses, would be observed in an ear with normal middle ear function.

1 December 2006 in Ear & Hearing
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
KBKarin Bork
Karin Bork
Objective: This study examined differences between the middle ears of two ethnic groups, Caucasian and Chinese young adults with normal hearing, using a new middle-ear measurement technique, wideband energy reflectance. The goal of this study was to determine whether the Chinese group had different middle-ear transmission properties than the Caucasian group. Design: There were 126 subjects (237 ears) between the ages of 18 and 32 yr, with 62 subjects in the Caucasian group and 64 subjects in the Chinese group. Wideband energy reflectance data were gathered using Mimosa Acoustics (RMS system version 4.0.4.4) wideband reflectance (WBR) equipment. Results: The Chinese group had significantly lower wideband energy reflectance than their Caucasian counterparts at higher frequencies; however, the Caucasian group had significantly lower energy reflectance at lower frequencies than the Chinese group. The Chinese group also had significantly lower admittance magnitude than the Caucasian group at lower frequencies. Because body size indices are more comparable between Caucasian females and Chinese males, the effect of body size could be potentially adjusted for by comparing the Caucasian female subjects with the Chinese male subjects. The differences observed between the Caucasian and the Chinese groups were no longer significant when the Caucasian female subjects were compared with the Chinese male subjects. Applying the Caucasian norms to four Caucasian adults with surgically confirmed otosclerosis resulted in an improved hit rate compared with the combined Caucasian and Chinese norms and the Chinese-only norms. Conclusion: Body size may play a role in the observed differences between the Caucasian and Chinese groups. The findings of this study suggest that further research is needed to investigate the effects of body size on wideband energy reflectance. It should be noted that factors other than body size may contribute to the observed differences. Chinese individuals may simply have different middle-ear characteristics than Caucasian individuals, which could affect WBR. In the meantime, overall test performance may be improved by using a more homogeneous norm when evaluating the middle ear of Caucasian or Chinese individuals with WBR.

1 February 2006 in Ear & Hearing
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
DDDreena Davies
Dreena Davies
This study examined differences between a group of normal-hearing Caucasian and Chinese young adults on six tympanometric parameters. The goal of this study was to determine if the Chinese group had different low and multifrequency tympanometry results than the Caucasian group. There were a total of 159 subjects (303 ears) between the ages of 18 and 34 years, with 76 subjects in the Caucasian group and 83 subjects in the Chinese group. Tympanometric data were gathered on a clinical immittance machine, the Virtual 310 equipped with a high frequency option. Four of the parameters-static admittance (SA), tympanometric width (TW), tympanometric peak pressure (TPP), and ear-canal volume (ECV)-were measured automatically at a standard 226 Hz frequency. The remaining two parameters-resonant frequency (RF) and SA up to 1,200 Hz-were measured by multifrequency, multicomponent tympanometry, using a mathematical approach. The Chinese group had significantly lower SA, wider TW, more positive TPP, and lower ECV than their Caucasian counterparts. The parameter of SA up to 1,200 Hz showed a significant group effect (Caucasian versus Chinese) until 900 Hz in the male group and up to 1,120 Hz in the female group. The Chinese group had significantly higher RF than the Caucasian group. Once the effect of body size was compensated by adjusting for the ear canal and the middle ear volumes, the differences observed between the Caucasian and the Chinese groups were no longer significant for tympanometric parameters obtained at standard probe tone frequency of 226 Hz; however, the effect was still significant for SA obtained at higher probe tone frequencies (560, 630, 710, 800, and 900 Hz) and for RF. Applying the Caucasian norms to a group of mainly Caucasian adults with surgically confirmed otosclerosis resulted in improved overall test performance when compared with the combined Caucasian and Chinese norms and the Chinese only norms. It seems that the body size plays a crucial factor in the observed differences between the Caucasian group and Chinese groups at a standard probe tone frequency of 226 Hz; however, other mechano-acoustical properties of the middle ear may contribute to these differences at higher probe tone frequencies. Findings of this study suggest that further research is needed to investigate the effects of body size on immittance measures with other ethnic groups. In the meantime, overall test performance may be improved by using a more homogenous norm when testing the Caucasian or Chinese individuals.

1 July 2013 in Ear & Hearing
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
MFM. Patrick Feeney
M. Patrick Feeney
KSKim S. Schairer
Kim S. Schairer
This article describes the effect of ethnicity, gender, aging, and instrumentation on wideband acoustic immittance (WAI). This is an important topic to investigate as the goal of any audiological test is optimize the test's sensitivity and specificity. One way to improve the test's sensitivity and specificity is to reduce the variability of the normative data. The impact of the aforementioned demographic characteristics on WAI norms has been reviewed, and where applicable its potential impact on clinical outcome has been discussed. Overall, differences observed between Caucasian and Chinese ethnic groups in adults population may warrant the use of ethnicity-specific norms especially for detection of otosclerosis; however, these differences in the school-aged children are not large enough to warrant the use of ethnicity-specific norms. It is important to explore whether the observed differences between Caucasian and Chinese ethnic groups is due to body-size indices and whether these differences can be replicated in other East Asian ethnic groups that share similar body-size indices. The differences observed between school-aged children and adults could also potentially impact clinical decision analysis. Therefore, use of age-specific norm is recommended. The differences in WAI between different systems are not clinically significant, and the use of instrument-specific norms does not result in improved test performance at least for the detection of otosclerosis. However, measuring WAI at ambient pressure (static) or at pressure corresponding to the peak (dynamic mode) could potentially impact the normative data and may prove to be clinically useful in cases of negative and positive middle ear pressure.

1 January 2009 in International Journal of Audiology
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
NLNeil Longridge
Neil Longridge
DBDesmond Bell
Desmond Bell
The purpose of this study was to examine patterns of energy of reflectance (ER) in preoperative and post-operative conditions in otosclerotic ears. It was also within the scope of this paper to investigate whether the changes in ER pattern post-operatively correlate to the improvement in hearing as measured by pure-tone audiometry. ER was measured in 15 surgically confirmed otosclerotic ears (mean age: 44 years) before and after the stapes surgery. The most prominent change in ER pattern following the surgery in majority of the subjects was a sharp and deep drop in ER value between 700–1000 Hz. There was also a secondary wider and smaller increase in ER value following the surgery between 2000–4000 Hz. Moreover, in most cases the drop in ER values following the surgery at low frequencies (≤1000 Hz) approximated the mean ER values in the normal group. Comparison of ER patterns with hearing improvement as measured by air conduction averaged across low (250–1000 Hz) and high (2000–6000 Hz) frequency bands before and after the surgery did not reveal any significant correlation. However, there was a general positive correlation trend for ER changes in low frequency band and AC changes, especially for high frequency bands. Changes in ER pattern may potentially be useful as an objective tool for monitoring the impact of the stapes reconstructive surgery and evaluating different surgical protocol.

1 May 2008 in Journal of the American Academy of Audiology
Verified
Journal Article
Closed access
Navid ShahnazNavid Shahnaz
Navid Shahnaz
Background: Wideband reflectance (WBR) provides important information about middle ear function and can explain variations in how the middle ear receives, absorbs, and transmits sound energy across a wide range of frequencies. However, as of yet, few normative studies have been published to guide clinicians in the practical applications of WBR. WBR has been measured more extensively in well babies than in neonatal intensive care unit (NICU) babies, who have significantly higher incidence of otitis media with effusion (OME). Purpose: The goal of this study was to explore the characteristics of the middle ear while using energy reflectance (ER) and normalized admittance in NICU babies who passed automated auditory brainstem response (AABR) and evoked otoacoustic emission (EOAE) hearing screening criteria and to compare these characteristics to patterns in normal hearing adults. This study was done to identify ways to implement WBR so it could improve hearing assessment in newborns. Methods: Thirty-one neonatal intensive care unit (NICU) babies with an average gestational age (GA) of 37.8 weeks (range: 32‐51 weeks) and 56 adults with normal hearing between the ages of 18 and 32 years served as subjects in this study. NICU babies and adults were tested using multifrequency tympanometry (MFT) and WBR. Results: WBR can be obtained on what appears to be a majority of NICU babies without other abnormal findings. Maximum absorption of the incident energy appears to occur at a narrower range of frequencies in normal NICU babies in comparison to normal hearing adults. This range becomes even narrower in NICU babies who fail EOAE screening. In most NICU babies who failed EOAE screening, ER values were closer to 1 (most incident energy is reflected) at a frequency below 3000 Hz. The measurements of normalized acoustic admittance may also be very useful and may supplement ER and tympanometric data in evaluating middle ear status.