| Objective:Unilateral sensorineural hearing loss（USNHL）is a condition in which one ear has varying degrees of sensorineural hearing loss,while the opposite ear is completely normal.Audiological examination can definitively diagnose USNHL,but the etiological diagnosis of USNHL remains a major challenge.With the continuous optimization of imaging technology,inner ear malformation（IEM）and cochlear nerve deficiency（CND）have been identified as one of the main causes of USNHL.Among the IEM classification,the bony cochlear nerve canal（BCNC）malformation is the most common.Therefore,HRCT and MRI provide valuable information in the etiologic diagnosis of USNHL,but the debate remains regarding which imaging modality is most ideal and should be the preferred study for patients with USNHL.The objective of this study was to analyze the common types of IEM in patients with USNHL,assess the proportion of BCNC malformation,and investigate the correlation between the diameter of the BCNC on HRCT and the development of the cochlear nerve（CN）on MRI.MRI was used as the golden standard for diagnosing CND,explore the feasibility of using BCNC malformation to diagnose CND,and finally to investigate whether HRCT can be the first choice for USNHL patients,and to analyze the audiological characteristics of CND patients,so as to provide new ideas and basis for the etiological diagnosis and intervention of USNHL patients.Methods:Forty-one patients who attended the Outpatient Department of Otolaryngology-Head and Neck Surgery at the Second Hospital of Jilin University from January 2018 to July2021 and were diagnosed as USNHL with IEM / CND by audiological and imaging examinations were selected for the study.Audiological examinations: auditory brainstem response（ABR）（including bone conduction and air conduction response thresholds）,auditory steady-state response（ASSR）,distortion product otoacoustic emissions（DPOAE）,acoustic immittance measurement and other objective audiological examinations.Subjective audiological examination as pure tone audiometry（PTA）.Imaging examinations: temporal HRCT and oblique sagittal MRI scan of the auditory nerve.Imaging requirements: patients were at least 10 months of age;all patients were recommended to underwent both HRCT and MRI,for patients who would undergo only one examination,HRCT is preferred to be the first tool to assess whether they had IEM.A total of 31 patients underwent both HRCT and MRI.IEM and CND classification criteria: the 2017 version of Sennaroglu classification criteria was used to evaluate the abnormal imaging presentation of patients.IEM includes complete labyrinthine aplasia,rudimentary otocyst,cochlear aplasia（including cochlear aplasia with normal labyrinth and cochlear aplasia with a dilated vestibule）,common cavity（CC）,cochlear hypoplasia（CH）（divided into CH-Ⅰ,CH-Ⅱ,CH-Ⅲ,CH-IV）,incomplete partition（IP）of cochlear（divided into IP-Ⅰ,IP-Ⅱ,IP-Ⅲ）,and enlarged vestibular aqueduct（EVA）,BCNC malformation（including hypoplastic and aplastic of BCNC）.The EVA is described when the midpoint is larger than 1.5 mm on axial sections.BCNC aplasia is considered as the canal is completely replaced by bone on mid-modiolar view,and the BCNC hypoplasia is described when the width is less than 1.4 mm.BCNC malformation is subdivided into 3 groups according to BCNC width: mild BCNC stenosis（1.0 mm ≤ BCNC width <1.4 mm）,severe BCNC stenosis（0.5 mm ≤ BCNC width <1.0mm）,and BCNC aplasia（<0.5 mm）;Internal auditory canal（IAC）is considered stenosis if the width of the midpoint of the IAC is smaller than 2.5 mm.（2）CND is divided into absent CN and hypoplastic CN,CN absent is diagnosed if CN was not shown at IAC;hypoplastic CN is defined as a cochlear nerve smaller than the facial nerve or the contralateral CN.Two physicians with at least 5 years of experience performed a blinded review and recorded the relevant data measurements at the abnormal sites.1.The types of abnormal imaging presentations were analyzed in 41 patients,and assessed the proportion of BCNC malformation.2.SPSS 25.0 software was used to statistically analyze the data,and Spearman correlation analysis was applied to investigate whether there was a correlation between the BCNC diameter as shown by HRCT and its CN development as shown by MRI in 31 patients,and α=0.01,P<0.01 was set to consider the two variables had correlation,with Spearman correlation coefficient r values ranging from [-1,+1]（positive values represent positive correlation between the two variables,negative values represent negative correlation）.For example,positive r value = 1 is completely linear correlated,r value ≥0.8 is high correlated,0.5 ≤ r value < 0.8 is significant correlated,0.3 ≤ r value < 0.5 is low correlated,r value < 0.3 is no correlated,r value = 0 is completely no linear correlated).3.MRI was used as the golden standard for diagnosing CND,and BCNC aplasia or hypoplasia shown by HRCT was used as the basis for diagnosing CND,and the chi-square test was performed to the diagnostic results of HRCT and MRI.Meanwhile,we calculated the sensitivity,specificity,positive predictive value and negative predictive value of HRCT in the diagnosis of CND to clarify the diagnostic efficacy of HRCT for CND.4.Using the ASSR test results as the standard,the mean response threshold was calculated for each frequency in 29 patients with CND,as well as for their speech frequencies（0.5,1,and 2 k Hz）,and the results were expressed as the mean ± standard deviation.Paired-sample t test was used to analyze the difference between the mean response threshold for speech-frequency and high-frequency（4 k Hz）,α=0.05 and P<0.05 considering the difference had statistically significant.Results:1.Forty of the 41 patients showed abnormalities on HRCT and one showed abnormalities on MRI alone.BCNC malformation was the most common among HRCT abnormalities,accounting for 82.5%（33/40）of all IEMs.Of the patients with BCNC malformation,21 had a simple BCNC malformation,11 had a combination of another type of IEM（9 with IAC stenosis;2 with vestibular-semicircular canal malformation）,and 1 had a combination of two other types of IEM（with IAC stenosis and vestibularhemispheric malformation）.Other types of IEM seen in this group of patients: 2 cases with IP-Ⅰ malformation（5.0%）;2 cases with cochlear aplasia with a dilated vestibule（5.0%）;1 case with bilateral IP-Ⅱ malformation with bilateral vestibular-semicircular canal malformation（2.5%）;1 case with CH-Ⅲ（2.5%）;and 1 case with CC malformation（2.5%）.31 patients had simultaneous oblique sagittal MRI scan of the auditory nerve.22 cases had CN absent,7 cases had CN hypoplasia,and 2 cases had normal CN.2.By Spearman correlation analysis,BCNC diameter was correlated with CN development（P=0.000<0.01）,and Spearman correlation coefficient r value=0.64.Based on the significance of r value,it was concluded that BCNC diameter was significantly and positively correlated with CN development,in other words,the smaller the BCNC diameter,the worse the CN development status.3.Thirty-one patients underwent HRCT and MRI at the same time,in which HRCT correctly diagnosed 28 cases,with one false positive and two false negative cases.The difference between HRCT and MRI for the diagnosis of CND was not statistically significant by chi-square paired test（P=0.187>0.05）,and the sensitivity,specificity,positive predictive value,and negative predictive value of HRCT for the diagnosis of CND were 93.1%,50%,96.4%,and 33.3%,respectively.The results showed that HRCT has high sensitivity and positive predictive value for the diagnosis of CND,indicating that the BCNC malformation shown by HRCT can be used as a basis for the diagnosis of CND,but in view of its low specificity and negative predictive value,the normal BCNC shown by HRCT cannot be used as a basis for excluding CND yet.4.The mean response thresholds for each frequency of ASSR in 29 CND patients were 83.86 ± 16.55 cor HL（0.5 k Hz）,87.00 ± 14.12 cor HL（1 k Hz）,90.93 ± 15.93 cor HL（2 k Hz）,and 95.69 ± 17.76 cor HL（4 k Hz）,respectively,which indicated that the CND patients in this group showed a decreasing trend on the audiological characteristic,and the mean response threshold of ASSR increased with increasing frequency.The four frequencies measured by ASSR were divided into two groups,namely the speechfrequency group（0.5,1,2 k Hz）and the high-frequency group（4 k Hz）.The mean response threshold of the speech-frequency group was 87.24 ± 15.84 cor HL;the mean response threshold of the high-frequency group was 95.69 ± 17.76 cor HL.Paired-sample t test was used to statistically analyze the above two results,P=0.000<0.05,the difference was statistically significant.The results confirmed that there was a significant difference between speech-frequency hearing and high-frequency hearing in CND patients,and their high-frequency hearing was worse than speech-frequency hearing.Conclusion:1.BCNC malformation is the most common type of IEM in patients with USNHL,followed by other types such as IAC stenosis,IP,and cochlear hypoplasia.2.BCNC diameter is significantly and positively correlated with CN development,in other words,the smaller the BCNC diameter,the worse the CN development status.3.The diagnostic result of HRCT with BCNC malformation as a basis for the diagnosis for CND is not significantly different from MRI.Therefore,based on the higher accessibility,shorter examination time,lower examination cost,and better predictive value for CND,we recommend HRCT as the first imaging tool for patients with USNHL to assess whether they have IEM and CND.4.Hearing characteristic of CND patients tends to decrease,and their hearing is better at speech-frequency（0.5,1,2 k Hz）than at high-frequency（4 k Hz）. |
PDF Full Text Request