Recognizing bisphosphonate-induced ear osteonecrosis in primary care: a case report.

INTRODUCTION: Medication-related ear canal osteonecrosis (MRECO) is a growing concern linked to prolonged anti-resorptive medication use. Despite primary care providers being key prescribers of these medications, there is limited information about MRECO in primary care literature. This article presents a case of bisphosphonate-induced osteonecrosis of the external auditory canal (EAC), emphasizing the vital role of primary care providers in identifying this rare yet significant side effect of anti-resorptive medication. MAIN SYMPTOMS AND CLINICAL FINDINGS: A 65-year-old female, on long-term alendronic acid for osteoporosis, presented to primary care with a 2-year history of left-sided ear blockage and itchiness. Despite prolonged topical treatment for ear wax, symptoms persisted, leading to an Otolaryngology referral. Microsuction revealed exposed bone in the left EAC. DIAGNOSES, INTERVENTIONS, AND OUTCOMES: A computed tomography scan confirmed bony erosion of the left EAC, and in the absence of other osteonecrosis risk factors, bisphosphonate-induced osteonecrosis was diagnosed. Management involved bisphosphonate discontinuation, regular aural toilet, and topical treatment, achieving complete ear canal epithelialisation within 6 months. CONCLUSION: MRECO, a rare complication of anti-resorptive therapy, is anticipated to rise with increasing antiresorptive medication use in the ageing population. Unexplained ear symptoms in those with a history of current or prior anti-resorptive therapy should raise clinical concern, prompting evaluation for exposed bone in the EAC. Raising awareness of MRECO among primary care providers is crucial for early diagnosis and timely management.

Malignant myoepithelioma of the external auditory canal - a rare case report with literature review and clinical importance of foramen of Huschke.

BACKGROUND: A malignant myoepithelioma is a rare tumor, mostly arising from the salivary glands. Myoepitheliomas of the ear have rarely been reported. The manuscript reports myoepithelial carcinoma of the external auditory canal (EAC) spreading to the infratemporal fossa. A clinician must be aware of anatomical variation of the bony EAC wall, such as the foramen of Huschke. This rare defect may be a pathway for spreading pathologies between these two anatomical regions. CASE REPORT: We present a case of osteoma-like stenosis of the EAC, which turned out to be an extremely rare malignant tumor. The preoperative MRI and PET/CT revealed that two parts of the tumor communicated through a defect in the antero-inferior portion of the bony ear canal. No distant metastases were detected. Subsequently, the tumor was resected from the ear canal and the infratemporal fossa en bloc. Perioperatively the defect in the EAC wall was suspected of the foramen of Huschke. After the surgery, the older scans of the patient from the past showed no presence of a congenital EAC wall defect. Therefore, the authors concluded that the tumor aggressively grew through the bone due to its biological nature. CONCLUSION: Malignant myoepithelioma of the external auditory canal is an extremely rare condition and could be misdiagnosed as other benign lesions. In cases of suspicious lesions, it is advisable to do a probatory biopsy from the EAC. Surgery is the treatment of choice in malignant myoepitheliomas, and regular follow-ups are essential to monitor for recurrence or metastatic disease. Any mass located at the antero-inferior portion of the EAC wall warrants close evaluation due to its potential for expansion from the EAC.

External auditory canal reconstruction using a novel mastoidoplasty technique during canal wall down mastoidectomy: how I do it.

BACKGROUND: While mastoid obliteration techniques have received much attention in decreasing the disadvantages associated with the resultant mastoid cavity from canal wall down procedures, techniques for an anatomically normal looking ear canal reconstruction to increase the feasibility of hearing aid fitting are less commonly discussed as an alternative. METHODS: Our mastoidoplasty technique basically utilises an inferiorly based periosteal flap with or without temporalis muscles and fascia to obliterate the epitympanum and reconstruct the external auditory canal (EAC). Stay sutures are used to keep them in place. For larger cavities, demineralized bone matrix (DBM) is used to obliterate the mastoid cavity and support the neo-EAC. CONCLUSIONS: The concept of our mastoidoplasty potentially provides a very useful alternative in recreating a near normal ear canal anatomy avoiding cavity problems as well as facilitating hearing aid fitting with canal type hearing aids after canal wall down mastoidectomy.

Measuring auditory event-related potentials at the external ear canal: A demonstrative study using a new electrode and error-feedback paradigm.

Although ear canal electroencephalogram (EEG) recording has received interest from basic and applied research communities, evidence on how it can be implemented in practice is limited. The present study involving eight male participants including the authors presents the utility of our ear canal electrode and method by demonstrating both comparability of ear canal EEG to those at nearby sites and distinctiveness that ear canal event-related potentials (ERPs) could have. For this purpose, we used the balanced noncephalic electrode reference and an experimental paradigm with an error-feedback sound. Clear auditory ERPs were detected at the ear canal sites with a sufficiently low noise level comparable with those at conventional sites. The N1c, a temporal maximum subcomponent, spread over the bilateral temporal sites, including the ear canals and earlobes. While consecutive signals are generally highly similar between the ear canal and the earlobe, the N1c was larger at the ear canal than the earlobe, as demonstrated by the conventional frequentist and the hierarchical Bayesian modelling approaches. Although an evident caveat is that our sample was limited in terms of size and sex, the general capability indicates that the structure of our ear canal electrode provides EEG measurement that can be used in basic and applied settings. Our experimental method can also be an ERP-based test that conveniently assesses the capability of existing and future ear canal electrodes. The distinctive nature of the ERPs to the error-feedback sound may be utilized to examine the basic aspects of auditory ERPs and to test the processes involved in feedback-guided behaviour of participants.

The role of MRI in the prenatal diagnosis and classification of fetal microtia.

OBJECTIVE: To investigate the role of MRI in the diagnosis and classification of fetal microtia. METHODS: Ninety-five fetuses with suspected microtia based on ultrasound and MRI performed within 1 week were enrolled in this study. The diagnosis based on MRI was compared with postnatal diagnosis. Among the microtia cases suspected on the basis of MRI, mild and severe cases were further classified. In addition, external auditory canal (EAC) atresia was evaluated by MRI in 29 fetuses with a gestational age > 28 weeks, and the accuracy of MRI in the diagnosis and classification of microtia was determined. RESULTS: Of 95 fetuses, 83 were considered to have microtia on the basis of MRI, 81 were confirmed to have microtia, and 14 were found to be normal according to postnatal diagnosis. Among 190 external ears in 95 fetuses, 40 ears were suspected to have mild microtia, and 52 ears were suspected to have severe microtia on the basis of MRI. According to the postnatal diagnosis, mild and severe microtia were confirmed in 43 and 49 ears, respectively. Among the 29 fetuses with a gestational age > 28 weeks, 23 ears were suspected to have EAC atresia according to MRI and 21 ears were ultimately confirmed to have EAC atresia. The accuracy of MRI in diagnosing microtia and EAC atresia was 93.68% and 93.10%, respectively. CONCLUSION: MRI shows good performance in diagnosing fetal microtia and has the potential to evaluate its severity on the basis of classification and EAC status. CLINICAL RELEVANCE STATEMENT: This study was aimed at investigating the role of MRI in the diagnosis and classification of fetal microtia. MRI shows good performance and can help evaluate microtia severity and EAC atresia, thus allowing for better clinical management. KEY POINTS: • MRI is a useful adjunct to prenatal ultrasound. • MRI has a higher accuracy rate than ultrasound in diagnosing fetal microtia. • The accurate classification of fetal microtia and the diagnosis of external auditory canal atresia through MRI may help guide clinical management.

Microsecretory adenocarcinoma of the external ear canal.

Microsecretory adenocarcinoma (MSA) is a recently described salivary gland tumor characterized by unique histomorphologic and immunohistochemical features as well as recurrent MEF2C::SS18 gene fusion. Since 2019, 24 cases have been reported in the literature, primarily arising in the oral cavity, with a single reported case arising in the parotid gland. Here, we present a case of MSA that arose in the external ear canal in an 89-year-old woman and was discovered during management of vertigo symptoms. Excisional biopsy of the lesion showed multiple fragments of squamous epithelium with hyperplastic changes and a distinct subepithelial infiltrating neoplasm composed of bland cells forming tubules and cords. Neoplastic cells expressed keratin, S100 protein, p63, and TLE1 and did not express p40, mammaglobin, pan-TRK, synaptophysin, or chromogranin by immunohistochemistry. SS18 gene rearrangement was shown with break-apart fluorescent in situ hybridization. Overall, the histomorphologic, immunohistochemical, and cytogenetic findings confirm a diagnosis of MSA arising in a unique extraoral location.

Disease recidivism after subtotal petrosectomy and ear canal closure.

PURPOSE: To describe the presentation, diagnosis, and management of chronic otitis media recidivism after subtotal petrosectomy and ear canal closure (STP). MATERIALS AND METHODS: Patients with temporal bone pathology detected during follow-up after STP were identified in the electronic medical record. Pertinent clinical details regarding surveillance plan, presentation, imaging findings, and revision surgery were collected and analyzed. RESULTS: A total of 10 patients were identified with recurrent or persistent pathology after STP. The median time to detection was 46 months (IQR 24-84). Five patients (50 %) had non-specific symptomatology, 4 patients (40 %) were completely asymptomatic, and 1 patient (10 %) was asymptomatic outside of two instances of mastoiditis with cochlear implant device infection treated with incision and drainage. One patient (10 %) was noted to have proptosis on examination, but no other patients had objective signs of disease at detection of disease recidivism. Nine (90 %) patients had pathology identified on preoperative imaging. All patients underwent revision surgery, with identification of cholesteatoma in 8 cases (80 %) and cholesterol granuloma in 2 cases (20 %). Extensive disease was noted in 6 patients (60 %), all of whom followed-up greater than 3 years from surgery. All patients tolerated revision surgery without complication. CONCLUSIONS: Recidivistic disease often remains clinically silent for extended periods of time after STP. Planned follow-up - with imaging or second look surgery - to facilitate early detection should be considered. Undetected disease recurrence or development may result in morbidity in a proportion of patients if surveillance is not performed.

Habituation of changed acoustics properties after canal wall down mastoidectomy.

PURPOSE: Our objective is to evaluate the effect of habituation on the altered ear canal acoustics after canal wall down mastoidectomy. METHODS: A total of 11 participants with single sided dry cavities and normal contralateral ear canals with normal hearing thresholds were included in the study. Filtered sound fragments were created that simulate the different acoustic properties based on the participants Real Ear to Coupler Difference (RECD) of the cavity ear and the contralateral normal ear canal. These filtered sound fragments are presented to the cavity ear canal and the contralateral normal ear canal using inserts earphones. Participants performed a subjective quality assessment of the sound fragments using paired comparison with a seven-point scale (- 3 till + 3). RESULTS: Mean assessment of sound quality revealed the following results; naturalness of sounds of the cavity ear canal is 0.29 (± 1.41; ns) in favour of the filtered sound fragment of the normal ear canal. Mean assessment of sharpness of sounds in the cavity ear canal is 1.55 (± 1.21, p = 0.55) in favour of the filtered sound fragment of the normal ear canal. Overall preference in the cavity ear canal was in favour of the normal ear canal acoustics 0.72 (SD ± 1.54 p = 0.224). CONCLUSIONS: Patients with cavity ear canals seem to habituate to their altered ear canal acoustics. Transforming the ear canal acoustics of the cavity ear to normal ear canal acoustics seem to sharpen the incoming sounds. Overall assessment of quality of sound of the normal ear canal acoustics is better than the cavity acoustics.

External Auditory Canal Carcinoma With An Unusually Extensive Invasion.

External auditory canal carcinoma, while starting out as a seemingly benign condition, if left untreated can have an aggressive course of disease and involve multiple lower cranial nerves. Squamous cell carcinoma remains the most frequent histological type of malignant neoplasm of the external auditory canal and temporal bone. Here we describe a patient with a history of chronic suppurative otitis media with an extensive spread, the tumour was reaching from the skull base to the oropharynx involving neurovasculature along with soft tissues and bones, as well as the cerebellum. The involvement of the recurrent laryngeal and hypoglossal nerves were the most unusual presentation here. The case differed from all previous reported cases as the spinal accessory nerve was to spared. Surgery and radiotherapy are the treatment options but for the inoperable cases presenting with an already poor prognosis, concomitant radiotherapy is the only choice.

Primary external auditory canal meningioma: Case report and review of the literature.

Meningiomas are tumors that arise from arachnoid cells attached to both the pia mater and the inner portion of the arachnoid. They are common intracranial tumors, representing 12-25% of intracranial neoplasms. Intracranial meningiomas can spread extracranially to involve surrounding structures, including the ear and temporal bone. Ectopic meningiomas, described as primary meningiomas with no intracranial involvement, are rare. We describe a case of a primary external auditory canal meningioma with no evidence of intracranial involvement. We present pre-operative imaging findings proving no intracranial involvement prior to surgical intervention. A literature review of this uncommon clinical entity is presented and a discussion regarding its prognosis and treatment is reviewed.

Diabetes and glycemic control in necrotizing otitis externa (NOE).

PURPOSE: Although the association between necrotizing otitis externa (NOE) and diabetes mellitus (DM) is well known, there is little knowledge in regards to the effects of DM and glycemic control on the outcome of NOE. The aim of the study was to determine the effects of DM duration and glycemic control, and in-hospital glycemic control on NOE severity. METHODS: A retrospective case series analysis, including all patients hospitalized between 1990 and 2018 due to NOE were included. Data collected included NOE disease characteristics, duration of DM, DM-associated comorbidities, glycated hemoglobin (HbA1c), urine microalbumin and in-hospital blood glucose measurements. Disease severity was defined based on duration of hospitalization (above or below 20 days) and need for surgery. RESULTS: Eighty-nine patients were included in the study. Eighty-three patients (94.3%) had DM. Preadmission HbA1c was 8.13% (5.8-12.6%). Forty-nine patients (65.5%) had mean blood glucose of ≥ 140 mg/dL and 26 (34.5%) had ≤ 140 mg/dL. DM duration was 157.88 months among NOE patients who required surgery, and 127.6 months among patients who were treated conservatively (p value 0.25). HbA1c in patients hospitalized < 20 days was 7.6%, and 8.7% among NOE hospitalized ≥ 20 days (p value 0.027). Seven patients with mean blood glucose of ≤ 140 mg/dL had Pseudomonas Aeruginosa (PA-NOE) (26.7%), in comparison to 25 (51.0%) with mean blood glucose measurement of ≥ 140 mg/dL (p = 0.045). CONCLUSIONS: HbA1c at admission is associated with longer hospitalization duration among NOE patients. Mean blood glucose during hospitalization was associated with a higher likelihood of PA infection, however, it had no effect on disease outcome.

Earable Ω (OMEGA): A Novel Clenching Interface Using Ear Canal Sensing for Human Metacarpophalangeal Joint Control by Functional Electrical Stimulation.

(1) Background: A mouth-free interface is required for functional electrical stimulation (FES) in people with spinal cord injuries. We developed a novel system for clenching the human metacarpophalangeal (MP) joint using an earphone-type ear canal movement sensor. Experiments to control joint angle and joint stiffness were performed using the developed system. (2) Methods: The proposed FES used an equilibrium point control signal and stiffness control signal: electrical agonist-antagonist ratio and electrical agonist-antagonist sum. An angle sensor was used to acquire the joint angle, and system identification was utilized to measure joint stiffness using the external force of a robot arm. Each experiment included six and five subjects, respectively. (3) Results: While the joint angle could be controlled well by clenching with some hysteresis and delay in three subjects, it could not be controlled relatively well after hyperextension in the other subjects, which revealed a calibration problem and a change in the characteristics of the human MP joint caused by hyperextension. The joint stiffness increased with the clenching amplitude in five subjects. In addition, the results indicated that viscosity can be controlled. (4) Conclusions: The developed system can control joint angle and stiffness. In future research, we will develop a method to show that this system can control the equilibrium point and stiffness simultaneously.

Biometric-Based Key Generation and User Authentication Using Acoustic Characteristics of the Outer Ear and a Network of Correlation Neurons.

Trustworthy AI applications such as biometric authentication must be implemented in a secure manner so that a malefactor is not able to take advantage of the knowledge and use it to make decisions. The goal of the present work is to increase the reliability of biometric-based key generation, which is used for remote authentication with the protection of biometric templates. Ear canal echograms were used as biometric images. Multilayer convolutional neural networks that belong to the autoencoder type were used to extract features from the echograms. A new class of neurons (correlation neurons) that analyzes correlations between features instead of feature values is proposed. A neuro-extractor model was developed to associate a feature vector with a cryptographic key or user password. An open data set of ear canal echograms to test the performance of the proposed model was used. The following indicators were achieved: EER = 0.0238 (FRR = 0.093, FAR < 0.001), with a key length of 8192 bits. The proposed model is superior to known analogues in terms of key length and probability of erroneous decisions. The ear canal parameters are hidden from direct observation and photography. This fact creates additional difficulties for the synthesis of adversarial examples.

Development of hearing in the big brown bat.

We studied the development of hearing in newborn pups of the big brown bat, Eptesicus fuscus. In the majority of pups, the opening of both outer auditory canals occurred on or before postnatal day (PND) 7, but in some, it extended to PND 11. Using repeated auditory brainstem response (ABR) recordings, we tracked the progressive development and maturation of auditory sensitivity in 22 E. fuscus pups every 3 days, from PND 10 to PND 31, with additional recordings in a subset of bats at 2 months, 3 months and 1 year of life. There was a profound increase in auditory sensitivity across development for frequencies between 4 and 100 kHz, with the largest threshold shifts occurring early in development between PND 10 and 19. Prior to PND 13-16 and when pups were still non-volant, most bats were unable to hear frequencies above 48 kHz; however, sensitivity to these higher ultrasonic frequencies increased with age. Notably, this change occurred near the age when young bats started learning how to fly and echolocate.

Changes in the ear canal microbiota of dogs with otitis externa.

AIMS: Otitis externa (OE), one of the most common ear diseases in dogs, is caused by bacterial pathogens such as Staphylococcus sp. To understand the network of microbial communities in the canine ear canal affected with OE, we performed a cross-sectional study using next-generation sequencing. METHODS AND RESULTS: Ear swab samples were collected from 23 OE-affected and 10 healthy control dogs, and the 16S rRNA gene sequenced using Illumina MiSeq. The otic microbiota in the OE-affected dogs showed significantly decreased alpha diversity compared to controls. The community composition also differed in the affected group, with significantly higher relative abundance of the phylum Firmicutes and the genus Staphylococcus (P = 0·01 and 0·04 respectively). Contrary to our expectations, the severity of the disease did not impact the otic microbiota in OE-affected dogs. CONCLUSIONS: The ear canal microbiota of OE-affected dogs is distinct from that of healthy dogs, irrespective of disease status. SIGNIFICANCE AND IMPACT OF THE STUDY: This study, one of the few detailed analyses of the otic microbiota, can provide practical information for the appropriate treatment of canine OE.

Prevalence and in vitro antifungal susceptibility of commensal yeasts in the external ear canal of cats.

BACKGROUND: Lifestyle factors such as hair length, the frequency of ear cleaning and bathing, age, cat rearing, and sex may contribute to opportunistic yeast infections in the external ear canal of cats. This study aimed to determine the prevalence of commensal yeast organisms in cats' external ear canals, evaluate their predisposing lifestyle factors, and test the susceptibility of Malassezia pachydermatis to antifungal agents. RESULTS: A total of 53 cats (33 male and 20 female) seronegative for feline leukemia virus and feline immunodeficiency virus were enrolled in this study. Their mean age (± standard deviation) was 6.04 (± 3.49) years. Fungal cultures and polymerase chain reaction tests were performed to identify the yeast species derived from the external ear canal. The association between lifestyle factors and the presence of M. pachydermatis was evaluated using Fisher's exact test. The susceptibility of M. pachydermatis to antifungal agents was also analyzed. M. pachydermatis was the most frequently recovered yeast species, with a prevalence of 50.94 % (95 % confidence interval [CI]: 36.84-64.94 %). There was an association between hair length and a positive culture for M. pachydermatis (p = 0.0001). The odds of a negative culture for M. pachydermatis among short-haired cats was 11.67 (95 % CI, 3.22-42.24) times higher than that among long-haired cats (p = 0.0002). There was also an association between the frequency of ear cleaning and the presence of M. pachydermatis (p = 0.007). The odds of a negative culture for M. pachydermatis in cats that were receiving ear cleaning at intervals of ≤ 2 weeks was 5.78 (95 % CI, 1.67-19.94) times greater than that of cats receiving ear cleaning at intervals greater than 2 weeks or never (p = 0.0055). Ranges of minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations for itraconazole, ketoconazole, miconazole, and terbinafine against M. pachydermatis were ≤ 0.063-4 and ≤ 0.063-≥32, ≤ 0.063-8 and 0.125-≥32, ≤ 0.063-≥32 and 0.5-≥32, and ≤ 0.016-1 and 0.125-8 µg/ml, respectively. CONCLUSIONS: M. pachydermatis was the most commonly identified yeast organism in the external ear canal of healthy cats. Hair length and the frequency of ear cleaning played a role in the colonization of M. pachydermatis. The M. pachydermatis isolates had various MIC levels for common fungicides.

The MO-meatocanalplasty: long-term results in the narrow external auditory canal with recurrent otitis externa or the inability to wear a hearing aid.

OBJECTIVE: The MO-meatocanalplasty is the oblique modification of the M-meatoplasty. The MO-meatocanalplasty was designed to address the superior quadrants of the meatus and the bony canal without the need for a retro-auricular incision. This retrospective analysis was performed to evaluate the long-term results of the MO-meatocanalplasty in patients with a narrow external auditory canal (EAC) with recurrent otitis externa or in patients unable to wear a hearing aid. METHODS: Twenty-two ears in twenty consecutive patients who received a MO-meatocanalplasty for a narrow EAC with recurrent otitis externa or the inability to wear a hearing aid were analysed retrospectively. There were no patients included with any type of previous or planned second stage tympanoplasty procedures. A follow-up period of 3 years was analysed for postoperative recurrent narrowing, the self-cleaning capacity of the EAC, the recurrence of otitis externa, the inability to wear a hearing aid, change in hearing level and for all types of aesthetical complaints. RESULTS: The MO-meatocanalplasty procedure was effective in 82% (n = 18). Postoperative recurrent narrowing was detected in 9% (n = 2). Insufficient self-cleaning capacity of the EAC was 9.1% (n = 2). The ability to wear a hearing aid was restored in all patients with the need for a hearing aid. No aesthetical complaints were reported. CONCLUSION: The MO-meatocanalplasty is an effective, safe and aesthetical accepted procedure to address the narrow meatus and external auditory canal. With this procedure, there is no need for a retro-auricular incision in order to create a well aerated, dry and self-cleaning EAC in patients with a narrow EAC with recurrent otitis externa or in patient with the inability to wear a hearing aid.

Who are good adult candidates for cartilage conduction hearing aids?

PURPOSE: Cartilage conduction hearing aids (CC-HAs) are novel hearing aids using the third hearing pathway of cartilage conduction. We assessed the efficacy of CC-HAs in adult hearing-loss patients who had various anatomical conditions of their ear canal(s) and determined who are good candidates for CC-HAs. METHODS: Patients (n = 37) were categorised into three groups of participants based on ear canal anatomy: (1) canal stenosis; (2) abnormal canal; (3) normal canal. After a 1-month free trial of normal usage, CC-HA-aided and unaided hearing thresholds (43 fitted ears) were determined using standard audiograms, after which participants could choose to purchase the device or not. Group and subgroup purchase rates were calculated along with the purchase reason (or not). Subgroup binary analysis of purchase rates was done according to hearing loss severity (< 70 dB and ≥ 70 dB) of unaided average air conduction (AC) hearing thresholds. RESULTS: CC-HA provided hearing improvements in all frequencies within each group. Overall, 60.47% of participants purchased a CC-HA after the trial. Over 70% participants with canal stenosis purchased CC-HAs, regardless of their AC hearing thresholds (severe vs. mild), and significantly more mild-loss participants in the abnormal canal group purchased their trial CC-HA compared to severe-loss participants (85.71% vs. 20%). CONCLUSION: Adult patients with ear canal stenosis or closure are the best candidates for CC-HAs, regardless of their hearing thresholds. Patients with more severe hearing loss accompanied by ear canal anomalies and patients with normal canal anatomy may not be good candidates.

Radiologic evaluation of the mastoid segment of the facial nerve tract in the intact temporal bone.

PURPOSE: To localize the facial nerve course in the mastoid segment and to measure its distances relative to the tympanic membrane. METHODS: This is a cross-sectional descriptive study. During 2019 in a tertiary hospital, 129 non-contrast and non-pathologic temporal CT images were studied in a tertiary hospital. Facial nerve distances were measured from the planes passing through the annulus in the axial cross-sections at superior, umbo, and inferior levels of the tympanic membrane. It was done in two different dimensions which are anteroposterior (toward the plane of the ear canal wall) and mediolateral (toward the plane of the tympanic membrane). RESULTS: The least mean anteroposterior distance between the facial nerve and the posterior ear canal wall was at the level of umbo (3.66 ± 0.76 mm). The nearest point of the nerve toward the tympanic membrane was the inferior level (- 0.03 ± 0.81 mm). Overall external ear canal lengths were statistically significantly lower in women rather than men. There was a reverse correlation between the age and the ear canal length. CONCLUSION: Posterior canalplasty seems to be safe unless dissection does not cross the plane of annulus. In this study, the safe margin was 1.4 mm in posterior canal wall drilling. It also should be performed carefully if it extends to the inferior side of the canal. Measuring the mediolateral dimension of the nerve toward the annulus in the axial CT images seems to be practically beneficial, especially in the inferior where the ear canal wall turns and might not act as a good landmark. Paying attention to this plane may reduce the risks of nerve injury in any procedures with transcanal approaches, particularly in inferior canaloplasty.

Acoustical role of ear canal in exposure to the typical occupational noise levels.

Background: Exposure to noise associated with injuries has become a public health issue in recent years. This study aimed to show the role of the acoustical structure of the ear canal on the typical occupational sound pressure levels at different frequencies. Methods: This cross-sectional study was done on 20-30-year-old participants. White noise was used at 3 levels, including 75, 85, and 95 dB as the stimulus sound pressure levels (SSPLs). The speakers had a 1.5-meter distance from the participants and at the height of 87 centimeters from the lab ground and were located in front of the participants. The SSPLs were measured outside (cavum part of the external ear) and inside the right ear of each participant. Measurements were done at the total sound pressure level and in the 1/1 octave frequencies. The duration for each measurement was 10 seconds. The independent sample t test was used for the statistical analysis, and the equality of means were rejected at p<0.05. Results: There were 30 (50%) males out of the 60 participants. The mean ± SD for the age of all the participants was 23.29±2.93 years. The total sound pressure level difference between the inside and outside of the ears of male and female participants was statistically significant (p<0.001) at the stimulus sound pressure levels. The peak resonance was observed in the frequencies 2000 Hz and 8000 Hz for males and 8000 Hz for females. Conclusion: The ear canal can amplify the sounds and increase the sound pressure levels. This amplification was found to be greater for males than for females.