Objective measurements of skull vibration during bone conduction audiometry

Vibratory auditory stimulation or bone conduction (BC) reaches the inner ear through both osseous and non-osseous structures of the head, but the contribution of the different pathways of BC is still unclear. In this study, BC thresholds in response to stimulation at several different locations including the eye were assessed, while the magnitudes of skull bone vibrations were measured on the front teeth in human subjects with either normal hearing on both sides or unilateral deafness with normal hearing on the other side. The BC thresholds with stimulation at the ipsilateral mastoid and ipsilateral temporal region were lower than the BC thresholds with stimulation at the other sites, as reported by previous works. The lower thresholds with stimulation at the ipsilateral mastoid and ipsilateral temporal region matched higher amplitudes of skull bone vibrations measured on the teeth, but only at frequencies below 1 kHz. With stimulation at the eye, the thresholds were significantly higher than those with stimulation at the bony sites in the frequency range of 0.25–4 kHz. While skull bone vibrations as measured on the teeth during stimulation at the eye were low for low frequencies, significant bone vibrations were measured at 3 and 4 kHz, indicating different pathways for BC for either the soft tissue or bony site stimulation. This finding contradicts a straightforward relationship between vibrations of the skull bones and BC hearing thresholds.

In order to differentiate between a conductive hearing loss (CHL) and a sensorineural hearing loss (SNHL) in the hearing-impaired individual, we compared thresholds to air conduction (AC) and bone conduction (BC) auditory stimulation. The presence of a gap between these thresholds (an air-bone gap) is taken as a sign of a CHL, whereas similar threshold elevations reflect an SNHL. This is based on the assumption that BC stimulation directly excites the inner ear, bypassing the middle ear. However, several of the classic mechanisms of BC stimulation such as ossicular chain inertia and the occlusion effect involve middle ear structures. An additional mode of auditory stimulation, called soft tissue conduction (STC; also called nonosseous BC) has been demonstrated, in which the clinical bone vibrator elicits hearing when it is applied to soft tissue sites on the head, neck, and thorax. The purpose of this study was to assess the relative contributions of threshold determinations to stimulation by STC, in addition to AC and osseous BC, to the differential diagnosis between a CHL and an SNHL. Baseline auditory thresholds were determined in normal participants to AC (supra-aural earphones), BC (B71 bone vibrator at the mastoid, with 5 N application force), and STC (B71 bone vibrator) to the submental area and to the submandibular triangle with 5 N application force) stimulation in response to 0.5, 1.0, 2.0, and 4.0 kHz tones. A CHL was then simulated in the participants by means of an ear plug. Separately, an SNHL was simulated in these participants with 30 dB effective masking. STUDY SAMPLE consisted of 10 normal-hearing participants (4 males; 6 females, aged 20-30 yr). AC, BC, and STC thresholds were determined in the initial normal state and in the presence of each of the simulations. The earplug-induced CHL simulation led to a mean AC threshold elevation of 21-37 dB (depending on frequency), but not of BC and STC thresholds. The masking-induced SNHL led to a mean elevation of AC, BC, and STC thresholds (23-36 dB, depending on frequency). In each type of simulation, the BC threshold shift was similar to that of the STC threshold shift. These results, which show a similar threshold shift for STC and for BC as a result of these simulations, together with additional clinical and laboratory findings, provide evidence that BC thresholds likely represent the threshold of the nonosseous BC (STC) component of multicomponent BC at the BC stimulation site, and thereby succeed in clinical practice to contribute to the differential diagnosis. This also provides evidence that STC (nonosseous BC) stimulation at low intensities probably does not involve components of the middle ear, represents true cochlear function, and therefore can also contribute to a differential diagnosis (e.g., in situations where the clinical bone vibrator cannot be applied to the mastoid or forehead with a 5 N force, such as in severe skull fracture).

Although human air conduction (AC) and bone conduction (BC) hearing are well investigated, there is a lack of information about BC hearing in most other species, the normal BC hearing thresholds have not been established. And animal model is vital for understanding the physiology of bone conduction hearing. Hence, in our study, the hearing thresholds in the guinea pigs were estimated by a regression of the amplitude of the compound action potential (CAP) with stimulation level and was found robust and gave a high resolution of the threshold level in the frequency range between 2 kHz and 20 kHz. The reference for the BC thresholds was the cochlear promontory bone velocity. This reference enables comparison of BC hearing in animals, both intra and inter species, which is independent on the vibrator and stimulation position. According to our comparable BC threshold, we can do some further research. The vibration was measured in three orthogonal directions where the dominating vibration directions was in line with the stimulation direction, here the ventral direction. The BC thresholds lay between -10 and 3 dB re 1 μm/s. The slopes of CAP growth function were similar for AC and BC at low and high frequencies, but slightly lower for BC than AC at frequencies between 8 and 16 kHz. This was attributed to differences in the stimulus levels used for the slope estimation and not a real difference in CAP slopes between the stimulation modalities. At the same time, the effect of a middle ear lesion, here modelled by severing the ossicles (ossicular discontinuity) and gluing the ossicles to the bone (otosclerosis), is investigated for both AC and BC. Two kinds of middle ear lesions, ossicular discontinuity and stapes glued to the surrounding bone, gave threshold shifts of between 23 and 53 dB for AC while it was below 16 dB when the stimulation was by BC. Statistically different threshold shifts between the two types of lesions were found where the AC threshold shifts for a glued stapes at 2 and 4 kHz were 9 to 18 dB greater than for a severed ossicular chain, and the BC threshold shifts for a glued stapes at 4 and 12 kHz were 8 to 9 dB greater than for a severed ossicular chain. Moreover, the direction of the vibration influences BC hearing also is investigated in our study. This direction sensitivity was investigated guinea pigs by providing BC stimulation in five different directions at the vertex of the guinea pig skull. The hearing thresholds for BC stimulation was obtained in the frequency range of 2 to 20 kHz by measurements of the guinea pigs’ compound action potential. During the stimulation by BC, the vibration of the cochlear promontory was measured with a three-dimensional laser Doppler vibrometer resulting in a set of unique three-dimensional vibration combinations for each threshold estimation. The sets of three-dimensional vibration at threshold were used to investigate six different predictors of BC hearing based on cochlear promontory vibration, three single direction (x, y and z directions in isolation), one linear combination of the three-dimension vibrations, one square-rooted sum of the squared vibration magnitudes, and one sum of the weighted three-dimensional vibrations based on a restricted minimum mean square error (MMSE) estimation. The MMSE gave the best predictions of the hearing threshold based on the cochlear promontory vibration while using only a single direction gave the worst predictions of the hearing thresholds overall. According to the MMSE estimation, at frequencies up to 8 kHz the vibration direction between the right and left side gave the greatest contribution to BC hearing in the guinea pig while at the highest frequencies measured, 16 and 20 kHz, the anteroposterior direction of the guinea pig head gave the greatest contribution. We do the further research to compare the vibrational patterns of human and guinea pig cochleae accurately, we developed and validated a novel finite element model of the guinea pig, leveraging it to analyze vibrational patterns in the cochlea. This approach is mirrored in our examination of the human cochlear model, providing granular insights into the nuances of human bone conduction hearing. The comparative analysis reveals that the guinea pig cochlea mirrors human cochlear vibrational patterns, thus serving as an efficient proxy for exploring human cochlear function. The convenient and comparable sites for bone conduction stimulation are identified as the human mastoid and the upper region of the guinea pig's skull. The cochlear vibration pattern encompasses a mix of rigid, rotational, and compressive motion.

Patients with elevated bone conduction (BC) thresholds are not considered a good candidate for otosclerosis surgery. Sometimes, it might be difficult to decide to operate these patients considering relatively poor cochlear function. However, viewpoints may vary among otologists. This study was undertaken to compare hearing outcome following otosclerosis surgery in patients who had bone conduction (BC) thresholds >or= 30 dB, and to investigate whether BC thresholds >30 dB has a negative impact on hearing outcome. Medical records of 111 patients who had undergone otosclerosis surgery were reviewed. Of 111 patients, 83 had undergone stapedotomy, and 28 stapedectomy. The patients were grouped based on preoperative four-tone BC threshold. Eighty-seven patients had average BC threshold <or= 30 dB, and were assigned to good-cochlear reserve group. The remaining 24 patients had average BC > 30 dB, and constituted poor-cochlear reserve group. Pre- and postoperative air conduction (AC) and BC thresholds, air-bone (AB) gap, vocal audiometry results and amount of deterioration in BC were determined. Mean postoperative AB gap was almost the same in both groups (14 and 15 dB) (P > 0.05). Percentage of AB gap = 10 dB favored good-cochlear reserve group (41 vs 29%)(P > 0.05). Analysis of mean hearing gain was slightly in favor of good-cochlear reserve group (19 vs 15 dB) (P > 0.05). Better BC thresholds were obtained postoperatively in good-cochlear reserve group (P < 0.001). Deterioration > 10 dB in BC was observed in 5.7 and 12.5% of the patients with good- and poor-cochlear reserve, respectively (P > 0.05). Based on the results of this small sample-size study, even though BC threshold of 30 dB was not considered a negative factor for hearing gain, otosclerosis surgery might have detrimental effects on postoperative BC thresholds in patients who had BC thresholds >30 dB.

To improve understanding of normal responses in infants by comparing air conduction (AC) and bone conduction (BC) auditory thresholds using both the auditory steady state response (ASSR) and behavioral testing methods in normal-hearing infants (6 to 18 months of age) and adults. At present, there are no correction factors available for estimating BC behavioral thresholds from BC ASSR thresholds, which is a barrier to clinical implementation of the ASSR. In addition, previous studies have reported infant-adult differences in AC and BC sensitivity, which suggest a "maturational" air-bone gap (ABG) that is not attributable to a conductive pathology; no study has yet compared AC and BC thresholds for either ASSR or behavioral methods in the same individuals. The objectives of the present study are: (1) to compare BC thresholds between methods and provide the initial step toward positing correction factors to predict BC behavioral thresholds, (2) to directly compare AC and BC thresholds to provide an accurate estimate of the maturational ABG, (3) to determine preliminary normal levels for BC and AC ASSRs to exponentially amplitude modulated stimuli, and (4) to investigate infant-adult differences in AC and BC thresholds using ASSRs and behavioral assessment tools. Participants were 23 infants (6.5 to 19.0 months of age) and 12 adults (17 to 50 years of age) with normal hearing. Thresholds were estimated at 500, 1000, 2000, and 4000 Hz using air- and bone-conducted stimuli for ASSRs and behavioral testing. The ASSR stimuli were exponential envelope modulated (amplitude modulation [AM]) at modulation frequencies of 78, 85, 93, and 101 Hz for 500, 1000, 2000, and 4000 Hz, respectively, presented simultaneously. Frequency-modulated (warble tone) stimuli were used for behavioral testing for both infants and adults, respectively. All stimuli were calibrated in dB HL. Thresholds were compared across frequency and between stimulus presentation modes, between age groups and assessment method. Normal levels for AC and BC ASSRs to AM stimuli were also calculated. The findings indicated that BC thresholds were, on average, 7 to 16 dB poorer for ASSR compared with visual reinforcement audiometry (VRA), but varied widely across infants. For infants, mean ABGs of 14 to 17 dB were found for low-frequency ASSR thresholds but mean ABGs for VRA thresholds were less than 10 dB. The preliminary normal levels for ASSR AM stimuli at 500, 1000, 2000, and 4000 Hz, respectively, were: (i) AC: 30, 30, 20, and 20 dB HL, and (ii) BC: 20, 20, 30, and 30 dB HL. There was a tendency for infant and adult ASSR thresholds to differ for BC, but not for AC. Behavioral thresholds for AC and BC were similar between infants and adults and across frequency. Infant-adult and AC-BC threshold differences are greater for ASSRs compared with behavioral measures. The results support the presence of a clinically significant maturational ABG in the low frequencies for infant ASSRs but not for VRA. The findings also show a significant offset between BC ASSR and BC VRA thresholds and large intersubject variability.

Background: Narrowband CE Chirps (NB CE-chirps) were used to provide the characteristics of compensation for the cochlear traveling wave delay and frequency specificity.Aim: The aim was to compare the objective frequency-specific hearing thresholds estimation by the use of NB CE-chirps ASSR and behavioural thresholds in normal hearing subjects and patients with the conductive hearing loss.Subjects and methods: The cases group comprised 35 ears of 25 patients with the conductive hearing loss with varying degree from mild to severe in severity and their age ranging from 15 to 60 years. They were compared with 20 ears of 10 adult control subjects with normal hearing thresholds, whose age ranged from 19 to 42 years. All cases and controls were subjected to pure-tone audiometry (PTA), tympanometry and auditory steady-state response (ASSR), using 4 NB CE-chirp for air conduction (AC) and bone conduction (BC) threshold estimation.Results: AC-ASSR estimated thresholds were statistically significantly higher than AC PTA thresholds at 500, 1000, 2000 and 4000 Hz in both the cases and the control groups. BC ASSR estimated thresholds were statistically significantly lower than BC PTA thresholds only at 500 Hz in the cases and statistically significantly higher than BC PTA thresholds only at 2000 Hz in the controls. There was a statistically significant positive correlation between AC-ASSR and AC PTA, and between ABG-ASSR and ABG PTA in the cases group.Conclusions: Auditory steady-state responses with NB CE-chirps is suitable tool for objective frequency-specific hearing threshold detection, that can be used for estimation of behavioural bone conduction thresholds in adults with conductive hearing loss, with more accuracy in the mid frequencies, and can estimate behavioural air conduction thresholds and air-bone gap more accurately in the higher frequencies 2000, 4000 Hz more than at 500 and 1000 Hz.

Bone conduction hearing in the Guinea pig and the effect of artificially induced middle ear lesions

Air conduction (AC), bone conduction (BC), and underwater-hearing thresholds were obtained on three samples of underwater swimmers. In Sample I, AC and BC hearing levels varied over a considerable range at the higher frequencies. Underwater hearing thresholds were positively correlated with BC thresholds. The loss of sensitivity upon immersion was negatively correlated with AC hearing levels. In Sample 2, underwater hearing thresholds of three divers having depressed AC hearing levels at 6 kHz and two divers having depressed AC and BC hearing levels were compared with underwater hearing levels of eight normal-hearing divers. Depressed underwater hearing levels occurred for the divers having combined AC and BC losses. Divers exhibiting only AC losses heard as well underwater as normal hearing divers. Maximum sensitivity for the normal hearing divers over the frequency range 1–8 kHz was −20 dB/μbar at 1 kHz. In a third sample, data were obtained on threshold sensitivity over the 125-Hz to 8-kHz frequency range. Maximum sensitivity of −23 dB/μbar was observed at 1 kHz.

To study normative thresholds and latencies for click and tone-burst auditory brainstem response (TB-ABR) for air and bone conduction in normal infants and those discharged from neonatal intensive care units, who passed newborn hearing screening and follow-up distortion product otoacoustic emission. An evoked potential system (Vivosonic Integrity) that incorporates Bluetooth electrical isolation and Kalman-weighted adaptive processing to improve signal to noise ratios was employed for this study. Results were compared with other published data. One hundred forty-five infants who passed two-stage hearing screening with transient-evoked otoacoustic emission or automated auditory brainstem response were assessed with clicks at 70 dB nHL and threshold TB-ABR. Tone bursts at frequencies between 500 and 4000 Hz were used for air and bone conduction auditory brainstem response testing using a specified staircase threshold search to establish threshold levels and wave V peak latencies. Median air conduction hearing thresholds using TB-ABR ranged from 0 to 20 dB nHL, depending on stimulus frequency. Median bone conduction thresholds were 10 dB nHL across all frequencies, and median air-bone gaps were 0 dB across all frequencies. There was no significant threshold difference between left and right ears and no significant relationship between thresholds and hearing loss risk factors, ethnicity, or gender. Older age was related to decreased latency for air conduction. Compared with previous studies, mean air conduction thresholds were found at slightly lower (better) levels, while bone conduction levels were better at 2000 Hz and higher at 500 Hz. Latency values were longer at 500 Hz than previous studies using other instrumentation. Sleep state did not affect air or bone conduction thresholds. This study demonstrated slightly better wave V thresholds for air conduction than previous infant studies. The differences found in the present study, while statistically significant, were within the test step size of 10 dB. This suggests that threshold responses obtained using the Kalman weighting software were within the range of other published studies using traditional signal averaging, given step-size limitations. Thresholds were not adversely affected by variable sleep states.

Distinct audiometric patterns in congenital round window atresia: A comparative study with common congenital middle ear anomalies

Objective To explore a novel surgical treatment for chronic suppurative otitis media (CSOM) and evaluate its treatment effect.Methods All 97 patients with chronic suppurative otitis media were chosen to be treated using this new surgical method.The skin of the external auditory canal was maintained intact.Open radical mastoidectomy was used to complete clean-up lesions ; the fascia of pedicled temporalis myofascia (PTM) was used to repair the tympanic membrane.The pedicled temporalis fascia,pedicled postauricular periosteal flap and intact skin of the external auditory canal were used in reconstruction of the posterior wall of external auditory canal.Pure tone audiometry (PTA) was performed before and after surgery,recording the air conduction and bone conduction thresholds at 0.5 kHz,1.0 kHz,2.0 kHz,4.0 kHz.The average of the patient's air and bone conduction hearing thresholds was recorded at the 4 frequencies.External auditory canal gauze was removed 3 weeks after surgery.All subjects were followed up for over 2 years.Comparison of hearing thresholds (PTA) was made ① Before and 4 weeks after surgery.② Before and 2 years after surgery.Hearing function comparison include air conduction (AC),bone conduction (BC) and air-bone gap (ABG) analysis.SPSS 16.0 was used in statistical analysis.Pre-and postoperated AC,BC and ABG were compared using T-test.P ＜ 0.05 was considered statistically significant.Results The healing rate of post-operated tympanic membrane was 95.88％ (93/97).Ninty-six ears had 2-year follow-up,and 1 patient was lost in follow-up.There were 2 patients presented with eardrum perforation during the follow-up,and the 2-year healing rate of tympanic membrane perforation was also 93.85％ (92/97).In 96 ears with 2-year followed-up,the average of pre-AC was (52.10 ±3.96) dB,the average of post-AC was (35.67 ±2.52) dB; the average of preABG was (36.6 ± 5.2) dB,and the average of post-ABG (± SD) was (12.14 ± 6.20) dB.Statistical analysis showed significant difference between preoperative and postoperative AC or ABG values (P ＜ 0.05).Conclusion The present surgical procedure broke through the existing conventional mastoidectomy of making a surgical incision in the posterior wall of the external auditory canal.This procedure cleared the lesion completely and preserved the physiological function of the external auditory canal.The acoustic systems and state of gasification to the mastoid tymnpanum were reconstructed,rehabilitated and maintained.The healing rate of hearing and tympanic membrane perforation was improved. Key words: Chronic suppurative otitis media; Tympanoplasty; External acoustic meatus; Tissue flaps

The auditory impact of a cochlear third window differs by its location in the scala vestibuli or scala tympani. Pathologic third window has been investigated primarily in the vestibular apparatus of animals and humans. Dehiscence of the superior semicircular canal is the clinical model. Fat sand rats (n = 11) have a unique inner-ear anatomy that allows easy surgical access. A window was drilled in the bony labyrinth over the scala vestibuli in 1 group (12 ears) and over the scala tympani in another (7 ears) while preserving the membranous labyrinth. Auditory brain stem responses to high- and low-frequency stimuli delivered by air and bone conduction were recorded before and after the procedure. Scala vestibuli group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.3 and 9.6 dB, respectively, and bone-conduction thresholds, 4.6 and 3.3 dB, respectively; after fenestration, air-conduction thresholds averaged 40.4 and 41.8 dB, respectively, and bone-conduction thresholds, -1 and 5.6 dB, respectively. Scala tympani group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.6 dB each, and bone-conduction thresholds, 7.9 dB and 7.1 dB, respectively; after fenestration, air-conduction thresholds averaged 11.4 and 9.3 dB, respectively, and bone-conduction thresholds, 9.3 and 4.2 dB, respectively. The changes in air- (p = 0.0001) and bone-conduction (p = 0.04) thresholds were statistically significant only in the scala vestibuli group. The presence of a cochlear third window over the scala vestibuli, but not over the scala tympani, causes a significant increase in air-conduction auditory thresholds. These results agree with the theoretic model and clinical findings and contribute to our understanding of vestibular dehiscence.

The level of improvement in the audiological results of Baha(®) users mainly depends on the patient's preoperative hearing thresholds and the type of Baha sound processor used. This investigation shows correlations between the preoperative hearing threshold and postoperative aided thresholds and audiological results in speech understanding in quiet of 84 Baha users with unilateral conductive hearing loss, bilateral conductive hearing loss and bilateral mixed hearing loss. Secondly, speech understanding in noise of 26 Baha users with different Baha sound processors (Compact, Divino, and BP100) is investigated. Linear regression between aided sound field thresholds and bone conduction (BC) thresholds of the better ear shows highest correlation coefficients and the steepest slope. Differences between better BC thresholds and aided sound field thresholds are smallest for mid-frequencies (1 and 2 kHz) and become larger at 0.5 and 4 kHz. For Baha users, the gain in speech recognition in quiet can be expected to lie in the order of magnitude of the gain in their hearing threshold. Compared to its predecessor sound processors Baha(®) Compact and Baha(®) Divino, Baha(®) BP100 improves speech understanding in noise significantly by +0.9 to +4.6 dB signal-to-noise ratio, depending on the setting and the use of directional microphone. For Baha users with unilateral and bilateral conductive hearing loss and bilateral mixed hearing loss, audiological results in aided sound field thresholds can be estimated with the better BC hearing threshold. The benefit in speech understanding in quiet can be expected to be similar to the gain in their sound field hearing threshold. The most recent technology of Baha sound processor improves speech understanding in noise by an order of magnitude that is well perceived by users and which can be very useful in everyday life.

Objective: Bone conduction (BC) stimulation closer to the cochlea has previously been shown to give higher cochlear promontory acceleration measured by laser Doppler vibrometry (LDV). This study is investigating whether stimulation closer to the cochlea also gives improved hearing sensitivity. Furthermore, the study compares shifts in hearing sensitivity (BC thresholds) and ear-canal sound pressure (ECSP). Design: BC hearing thresholds and ECSP have been measured for stimulation at two positions: the existing bone-anchored hearing aid (BAHA) position, and a new bone conduction implant (BCI) position that is located closer to the cochlea. Study sample: The measurements were made on 20 normal-hearing subjects. Results: Depending on frequency, the ipsilateral hearing threshold was 3–14 dB better, and the ipsilateral ECSP was 2–12 dB higher for the BCI than for the BAHA position, with no significant differences between threshold and ECSP shifts at group level for most frequencies, and individually only for some subjects. Conclusions: It was found that both the objective ECSP and the subjective hearing threshold measurements gave similar improvement as previous LDV measurements for stimulation closer to the cochlea. One exception was that the LDV measurements did not show the improved sensitivity for frequencies below 500 Hz found here.

ObjectiveTo evaluate the clinical efficacy and safety of hydrogen inhalation in improving hearing loss in patients with long-term survival of nasopharyngeal carcinoma after radiotherapy.MethodsThe eustachian tube dysfunction score, pure tone air conduction threshold, bone conduction threshold, the score of tympanogram and otoscope were prospectively observed in patients with deafness after radiotherapy only or combined radiotherapy and chemotherapy for nasopharyngeal carcinoma. Paired t test and one-way analysis of variance were used to analyze the data before and after treatment.ResultsA total of 17 patients were observed. The median time from radiotherapy to now was 228 months, and the median time from the diagnose of deafness to now was 92 months. After 4 weeks of hydrogen inhalation, the score of eustachian tube dysfunction, air conduction and bone conduction hearing thresholds were significantly reduced, P values were 0.0293, 0.0027, 0.0404, respectively. The mean air-bone gap, the score of otoendoscopy and tympanogram were also decreased, but the differences were not significant (P = 0.2079, P = 0.0536, P = 0.1056). Patients with radiotherapy alone and concurrent chemo-radiotherapy had significantly lower air conduction hearing threshold after hydrogen absorption (P = 0.0142, P = 0.0495). The results of air and bone hearing thresholds before, 4 and 12 weeks after hydrogen inhalation showed a descending trend. The air and bone hearing thresholds before hydrogen inhalation were 74.69 ± 27.03 dB and 45.70 ± 21.58 dB, respectively. At the 12th week, the mean values of air and bone hearing thresholds were the lowest, which were 66.88 ± 20.88 dB and 40.94 ± 18.93 dB, respectively, but there was no significant difference in air and bone hearing thresholds among all groups (P = 0.6755, P = 0.7712). After hydrogen inhalation treatment, no adverse reactions such as nosebleed, chest pain, dyspnea, nausea, vomiting, dizziness, earache and allergic reaction were observed.ConclusionThis is the first prospective study on the effect of hydrogen inhalation on hearing improvement in patients with deafness after radiotherapy/chemotherapy for nasopharyngeal carcinoma, suggesting that continuous hydrogen inhalation may be an alternative rehabilitation therapy for these patients.