Study Of The Anatomy Related To Adult Cochlear Implantationbased On CT Images

Objective To study the anatomy of adult cochlear implantation(CI) pathway by computed tomography(CT):1.Selections of the optimal CT imaging technology which observe the degree of mastoid air cell, the pathway of vertical facial nerve(VFN) and chorda tympani nerve,the form of facial recess, round window,round window niche and cochlear can provide reliable and accurate informations for adult patients before CI.2.Using the threshold value method with CT attenuation value which measure volume of mastoid air cell that relates to the location of VFN can provide a new method of quantitative measurement for the adult mastoid air cell and judge the relation between it and the location of VFN.3.Multiple planar CT measurement and circumference formula calculation to the outer length of cochlea can provide a new method for adult cochlear length and CI electrode insertion depth reference. Methods Seventy-one temporal bones with post-lingual deafness adult patients were scanned by64-slice spiral CT (MSCT) and transferred into post-processing workstation. Among them, anatomical observation to CI pathway of forty-three cases. Volume measurement by threshold value software of thirty-nine cases were analyzed the correlation between the degree classification of mastoid air cell and the distance from the posterior wall of external auditory meatus osseous(D1), round window niche (D2)and lateral margin of mastoid bone(D3) to VFN respectively. And multiple planar CT measurement and circumference formula calculation to the outer length of cochlea of nine cases were compared with Chinese scholars, research methods. All statistical analyses were performed using SPSS17.0software package. P <0.05was considered statistically significant. Result The axial of round window niche level can observe the mastoid air cell degree and classification clearly. The total of3categories: good(group A), bad(group B) and without of it(group C).The transparent reconstruction and pseudo color staining can observe three-dimensional mastoid air clearly,and the degree, distribution and shape of it. The axial and oblique sagittal level can observe the position between the anterior margin of sigmoid sinus and the posterior margin of external auditory canal, and judge whether sigmoid sinus ante-displacement or not.The axial,coronal and oblique sagittal level can observe the position between bulb of jugular vein and the edge of lower cochlea,and judge whether high jugular bulb or not. The coronal and oblique sagittal level can observe the position between middle cranial fossa brain plate and the edge of horizontal semicircular canal,and judge whether low middle cranial fossa brain plate or not. the axial of pyramidal eminence and oblique sagittal of round window niche level can observe the shape, position and components of facial recess clearly. The axial and oblique sagittal of facial nerve, chorda tympani nerve tube can observe the pathway,segment and origin of them. The axial and coronal of round window niche level can observe the shape,depth and size of it clearly, and the minimum intensity projection(Min-IP) can observe the density of it.The axial of round window niche and modiolus level can observe the shape,length of the low,middle and top of cochlear ducts clearly, and the long oblique of them level can observe the shape of their circumference respectively. The long oblique of semicircular canal level can observe the shape of them respectively. The Min-IP can observe the membrane structure of inner ear. The volume rendering(VR) can observe three-dimensional vestibular window,vestibular,semicircular canal,bony cochlea and the number of cochlear duct. The pseudo color staining and image fusion can observe three-dimensional space of cochlea and auditory ossicular chain in temporal bone.The study of mastoid air cell volume range was about1.46~16.1ml.The male was about6.62±3.98ml and the female was about6.83±4.01ml, and no statistically significant between the sex.The left side was about6.57±3.87ml and the right side was about6.43±3.92ml, and no statistically significant between two sides.In group A the mastoid air cell average volume was about7.35ml,and D1, D2and D3results were4.45±0.23mm,5.28±0.11mm and24.44±8.20mm respectively.In group B the mastoid air cell average volume was about3.56ml,and D1, D2and D3results were5.23±0.09mm、5.56±0.20and24.32±2.38mm respectively. In group C the mastoid air cell volume was about0ml,and D1, D2and D3results were5.83±0.13mm、5.73± 0.14mm及22.19±3.52mm respectively. No statistically significant for D3in group A and B,and for D2in group B and C. Statistically significant for the rest of D1,D2and D3in group A, B and C each other. The study of length of cochlear outer was about26.38~32.34mm.The male was about28.73±1.57mm and the female was about29.14±4.21mm, and no statistically significant between the sex.The left side was about28.69±1.62mm and the right side was about29.16±1.71mm, and no statistically significant between two sides.The result compared with virtual endoscopy(VE) mothed was statistically significant,but no statistically significant with microsurgical anatomy mothed and cochlea segmentation and centroid extraction method. Conclusion MSCT imaging technology can observe the anatomy related to adult CI pathway detailed, and provide reliable,accurate imaging information for the adult clinical CI operated successfully. The threshold value method with CT attenuation value which can measure volume of mastoid air cell accurately and quantitatively is a new,simple and convenient method.There is a certain relation between the degree of mastoid air cell and the location of VFN.The better degree of it,the location of VFN closer to round window niche and posterior wall of external auditory meatus osseous.So the clinic measures volume of mastoid air cell quantitatively for judging the location of VFN that can help clinic to select the CI surgery strategy. Multiple planar CT measurement and circumference formula calculation to the outer length of cochlea which can provide reference for adult CI electrodes implanted depth is a new,simple,quick and noninvasive method.