Morphological Study On Cochlea And Cochlear Implantation Surgery

Cochlear implantation(CI)is the most effective treatment for severe to profound sensorineural hearing loss.However,the CI surgery itself may result in damage of cochlear structure which is important to have a better speech understanding performance postoperative.Recent studies showed that with soft,slim and proper electrode design and atrauma insertion technique,the trauma caused by CI operation may be reduced.Although there were a lot of studies of cochlear anatomy from different perspectives,the results were various.Therefore,a further detailed and comprehensive knowledge of cochlear size,shape and fine structure is needed.Researches showed that cochlear length can vary by 40 percent between the longest and the shortest cochlea even in the subjects with normal development of cochleae.The cochlear length is closely related to the insertion depth angle of electrode,which may influence the postoperative speech performance and insertion trauma.But the assessment techniques now could not realize individualized real-time measurement to choose the specific length of cochlear electrode.Besides,the coiling pattern of cochlea was important for cochlear implantation.The cochlear coiling pattern of the first and the second turn of cochlea had correlations with the introduction of electrode and the insertion trauma.And our clinical experience of CI surgery reminded that the resistance of inserting electrode would be greater when the electrode passing through 180 degree of cochlea.This site was also the most reported of insertion trauma of CI.Although there was no report about the correlation between it and the tilt angle of cochlear base,we speculated they had a closely relationship.Authors suggested that measuring the parameters of cochlear size and width of cochlear nerve canal was important for diagnosis of congenital sensorineural hearing loss(SNHL)and cochlear implant.But the measuring methods and the measuring planes were confusing.The results also had a significant variance.This led confusion to clinical application.Besides,previous measuring methods could not realize individualized real-time measurement and accurately unique location of the measurements.Studies showed that the liner insertion length,the insertion depth angle and the scalar localization of cochlear electrode as well as insertion trauma had correlations with postoperative speech understanding performance.However,there were few reports about the correlations between these parameters and the cochlear morphology and cochlear size.Besides,the X-ray is the most important assessment method of cochlear electrode.But the patient needs to take a forced position during the examination.What is more,the image of X-ray had a low spatial resolution.Authors suggested the cone beam computed tomography(CBCT)was more suitable for assessing of cochlear electrode because it had the advantages of low-radiation and high spatial resolution.The purposes of this study:1.To establish measurement methods of cochlear length,cochlear height,length and width of cochlear base,tilt angles and width of cochlear nerve canal with a platform of computed tomography three-dimensional multiplanar reconstruction and curve planar reconstruction techniques,which could help realize individualized real-time measurement.To analyze the relationship between these parameters and to discuss the potential implications for cochlear implants of them.2.To measure the parameters of cochlear size and cochlear coiling pattern as well as the width of cochlear nerve canal in cochlear implant pediatric candidates on consensus panels of the cochlear coordinate system.These parameters was measured with a platform of computed tomography three-dimensional multiplanar reconstruction and curve planar reconstruction techniques,which could help realize individualized real-time measurement.And compare these parameters of the group of cochlear implant pediatric candidates with the group of children with normal bone-conduction hearing.3.To study the postoperative situation of cochlear electrode from straight and perimodiolar implants on CBCT.These subjects were made up of pediatric candidates from national project of cochlear implants and adults of postlingual deafness implanted with the same cochlear electrode during the same period.We used the multiplanar reconstruction and curve planar reconstruction techniques to measure the liner insertion length and the insertion depth angle of cochlear electrode and observed the scalar localization of cochlear electrode.We analyzed the relationship between these parameters and the cochlear length as well as cochlear tilt angles to discuss the reasons and countermeasures of dislocation of electrode.PartⅠ Cochlear Size and Shape Variability and Implications inCochlear Implantation Surgery ObjectiveTo study variations in cochlear size and shape with potential implications for cochlear implants with a platform of computed tomography three-dimensional multiplanar reconstruction and curve planar reconstruction techniques,which could help realize individualized real-time measurement..MethodsA total of 310 normal developed cochleae from 155 subjects with age range from 1 to 73 years old were included in this study.The computed tomographic scan images of their temporal bones were recorded and reconstructed with three-dimensional multiplanar reconstruction and curve planar reconstruction techniques.The measurements were performed on consensus panels of the cochlear coordinate system.1.The length of cochleaA curved line was drawn from midpoint of the round window(0 degree)to the endpoint of helicotrema fit along the outer lateral wall of cochlea on cochlear view.We measured the liner length from the 0 degree to the end of the half turn(180 degrees,1/2TL),the end of three quarters of the basal turn(270 degrees,3/4TL),the end of the first turn(360 degrees,1TL),the end of the second turn(720 degrees,2TL)and the endpoint of helicotrema(cochlear length,CL)with three-dimensional curve planar reconstruction technique.2.The diameters of cochlear baseThe length of the cochlear base(BL)was the largest distance from the mid-point of the round window through the modiolus to the lateral wall of the basal turn and the width of the cochlear base(BW)was the perpendicular distance of the length of the cochlea base crossing the modiolus.These two parameters were measured on cochlear view.3.Tilt anglesThe tilt angle within the first turn(α)was the angle between the two lines with the tip point at 180 degrees and one to the point at 0 degree and another to the point at 360 degrees of the cochlea on oblique axial plane.The angle between the first and second turn of the cochlea(γ)was the angle between the two lines with the tip point at 270 degrees and one to the point at 90 degrees and another to the point at 450 degrees of the cochlea on oblique sagittal plane.Results1.The measurement results showed that cochlear size and shape vary greatly among individuals.CL ranged from 30.7 mm to 42.2 mm with a mean length 35.8 ± 2.0 mm.The mean 1/2 TL was 12.6 ± 0.6 mm and the mean 3/4 TL was 17.7 ± 0.8 mm and the mean 1TL was 21.1 ±1.1 mm and the mean 2TL was 32.0 ± 1.6 mm.The mean length and width of cochlear base were 9.04 ±0.31 mm and 6.33 ± 0.28 mm and they had a positive correlation(r=0.802,P=0).2.The length and width of cochlear base had positive correlations with 1/2TL(r=0.526 and r=0.625),3/4TL(r=0.633 and r=0.729),1TL(r=0.658 and r=0.754),2TL(r=0.677 and r=0.795)and CL(r=0.622 and r=0.769)respectively.3.The mean tilt angle α was 9.72 ±1.85 degrees and the angle γ was 14.90 ± 1.36 degrees.The ratio of the length to width of cochlear base had positive correlations with angle α(r=0.117,P=0.040)and angle γ(r=0.141,P=0.013).Conclusions1.The significant variations of the cochlear size and shape suggest that personalized cochlear implant treatment is needed.2.There is a strong positive correlation between the length and width of cochlear base to the linear length of cochlea and the width of cochlear base may be a better predictor to the length of cochlea.3.The ratio of the length to width of cochlear base has positive correlations to the angle between the first and second turn as well as the angle within the first turn of the cochlea.And the cochlear coiling pattern can be predicted by the ratio of length to width of cochlear base.PartⅡ Computed Tomography Study of Cochlea and Cochlear Nerve Canal in Congenital Severe Sensorineural Hearing Loss ChildrenObjective To measure the parameters of cochlear size and coiling pattern as well as the width of cochlear nerve canal in cochlear implant(CI)pediatric candidates on consensus panels of the cochlear coordinate system with a platform of computed tomography(CT)three-dimensional multiplanar reconstruction and curve planar reconstruction techniques,which could help realize individualized real-time measurement.MethodsA total 42 cases(84 ears)of cochlear implant pediatric candidates with grossly normal cochlea image were included in this study(age ranged from 10 months to 14 years old,with a mean age of 5.52 years old).And also 42 cases(84 ears)of children matched with age and sex and with normal bone-conduction hearing were compared as control.The computed tomographic scan images of their temporal bones were recorded and reconstructed with three-dimensional multiplanar reconstruction and curve planar reconstruction techniques.The measurements were performed on consensus panels of the cochlear coordinate system.1.Parameters of cochlear size A curved line was drawn from the midpoint of round window of cochlea(0 degree)to the terminal point of the apical turn fit along the outer lateral wall of the cochlea.We measured the liner length of this curved line with three-dimensional curve planar reconstruction techinique and this was the cochlear length(CL).Cochlear height(CH)was measured from the lower base of the basal turn to the upper base of the apical turn on oblique sagittal view.The length and width of cochlear base(BL & BW)were measured with the same methods described in Part Ⅰ.2.Parameters of cochlear coiling.The tilt angle within the first turn of cochlea(α)and angle between the first andsecond turn of cochlea(γ)were measured with the same methods described in Part Ⅰ.3.Width of cochlear nerve canalThe width of cochlear nerve canal was measured on oblique axial planes(axial CNC)and on oblique sagittal planes(sagittal CNC)respectively.The width of cochlear nerve was the performed tangentially to the two inferior extremities of the X-shaped modiolus.Results1.Cochlear sizeThe mean values of BL,BW,CH and CL of CI group were 8.77 ± 0.42 mm,6.17 ± 0.37 mm,3.57 ± 0.19 mm,35.2 ± 2.1mm.The mean values of BL,BW,CH and CL of control group were 9.06 ± 0.35 mm,6.29 ± 0.32 mm,3.69 ± 0.24 mm,35.8 ± 1.88 mm.BL,BW,CH and CL were significantly smaller in cochlear implant candidates than in control group(BL: P=0;BW: P=0.045;CH: P=0.001;CL: P=0.045).2.Cochlear coiling patternThe mean values of α and γ of CI group were 8.82 degrees and 14.62 degrees.The mean values of α and γ of control group were 8.97 degrees and 14.82 degrees.There were no significant differences of these two angles between CI group and control group(α: P=0.473;γ: P=0.365).3.Width of cochlear nerve canalThe mean values of axial CNC and sagittal CNC of CI group were 1.76 ± 0.19 mm and 1.93 ± 0.22 mm.The mean values of axial CNC and sagittal CNC of control group were 1.88 ± 0.23 mm and 2.04 ± 0.22 mm.Axial CNC and sagittal CNC were significantly smaller in CI group than in control group(P=0).4.Correlation of the parameters we measuredAny two parameters of BL,BW,CH,CL,axial CNC and sagittal CNC had a positive correlation(aixal CNC & CH: P=0.006;axial CNC & CL: P=0.002;others: P=0).ConclusionsMeasuring the parameters of cochlear size and width of cochlear nerve canal helpdiagnose congenial sensorineural hearing loss more accurately.Preoperative individualized real-time measurement could help choose the proper cochlear electrode and modify surgical program in time.Part Ⅲ Cochlear Electrode Insertion Depth Angle and Scalar Localization Determined by Cone Beam Computed TomographyObjectiveTo study the postoperative situation of cochlear electrode from straight and perimodiolar implants on cone beam computed tomography(CBCT),which were made up of pediatric candidates from national project of cochlear implants and adults of postlingual deafness implanted with the same cochlear electrode during the same period.We used the multiplanar reconstruction and curve planar reconstruction techniques to measure the liner insertion length and the insertion depth angle of cochlear electrode and observed the scalar localization of cochlear electrode.We analyzed the relationship between these parameters and the cochlear length as well as cochlear tilt angles to discuss the reasons and countermeasures of dislocation of electrode.MethodsA total of 71 cases of patients implanted with electrode of SONATA ti100 and CI24RE(CA)from March 2014 to November 2016 were studied.These patients were made up of pediatric candidates from national project of cochlear implants and adults of postlingual deafness implanted with the same cochlear electrode during the same period.All the patients should cooperate with image examination.All the CBCT images were import to Osirix.The insertion depth angle was measured on cochlear view.The cochlear view was reconstructed through the basal turn of cochlea and the center of modiolus on the plane contained cochlear base described in the cochlear coordinate system.The other two planes bisected the cochlea through the modiolus as oblique sagittal plane and oblique axial plane were used to observe the scalar localization of cochlear electrode.We measured the liner insertion length of electrode under the interface of 3D curved MPR.We analyzed the relationships between the liner insertion length,the insertion depth angle,the scalar localization of cochlear electrode and the parameters of cochlear size,cochlear length,tilt angles.Results1.The measurement results showed the insertion depth angle and liner insertion length varied greatly among individuals.The mean insertion depth angle was 702 ± 53 degrees and the mean liner insertion length was 30.02 ± 1.29 mm in the group of SONATA ti100.The mean insertion depth angle was 441 ± 45 degrees and the mean liner insertion length was 18.4 ± 1.0 mm in the group of CI24RE(CA).2.The length and width of cochlear base both had negative correlations with the insertion depth angle in the two groups(SONATA ti100: r=-0.768,P=0& r=-0.678,P=0;CI24RE(CA): r=-0.467,P=0.008& r=-0.471,P=0.008).The liner insertion length of the electrode had a positive correlation with the insertion depth angle in the two groups(SONATA ti100: r=0.578,P=0;CI24RE(CA): r=0.748,P=0).3.6/30 cases of electrode of CI24RE(CA)were located in the scala vestibule and the site of the dislocation was the 180 degrees of cochlea.The tilt angle within the first turn of cochlea and angle between the first and second turn of cochlea had significant differences between the group of patients with electrode located in the scala vestibule and the group of patients with electrode located the scala tympani(10.28 degrees vs 8.75 degrees,P=0.006;15.25 degrees vs 14.00 degrees,P=0.033).ConclusionsThe insertion depth angle and the liner insertion length of electrode varied greatly among individuals.These differences result from the difference of cochlear size.The dislocation of electrode may due to the coling pattern of cochlea as well as the design of electrode and the surgical techniques.Conclusions1.With the cochlear coordinate system and the platform of computed tomography three-dimensional reconstruction technique,we established the measuring methods of cochlear length at a specific site,cochlear height,size of cochlear base,tilt angles and width of cochlear nerve canal from normal developed cochleae.This could realize preoperative prediction about the electrode length that implanted in a specific location individualized and accurately.2.The significant variations of the cochlear size and shape suggest that personalized cochlear implant treatment is needed.The width of cochlear base may be a better predictor to the length of cochlea.The cochlear coiling pattern can be predicted by the ratio of length to width of cochlear base.3.Measuring the parameters of cochlear size and width of cochlear nerve canal not only could help diagnose congenial sensorineural hearing loss more accurately but also could help choose the proper cochlear electrode and modify surgical program in time.4.The insertion depth angle and the liner insertion length of electrode varied greatly among individuals.These differences result from the difference of cochlear size.The dislocation of electrode may due to the coiling pattern of cochlea,the design of electrode and the surgical techniques.