Study Of 64-Slice CT In 3-Dimentional Reconstruction Of Post-Operation Cochlear Implantation

OBJECTIVE: Study the correlation between electrode and auditory nerve compound action potential threshold (ECAP) by electrical evoking through measuring electrode insertion depth, the distance between the modiolar and electrode, the position of electrode in scala tympani or vestibular, neural response telemetry's distance-type threshold.METHODS: Collecting 18 patients who were severe sensory neural hearing loss, that planted artificial cochlea in First Affiliated Hospital of Guangxi Medical University from the March of 2004 to November in 2009.Recording patients'sex, age, residual hearing, preoperative diagnosis, implanting time, implant electrode's type and postoperative complications,and so on. Measure the depth of electrode imbedded in cochlea, the distance between electrode and modiolar, ECAP threshold after the electrode in cochlea was three-dimensional contour reconstituted by 64-slice spiral CT, then analyze the correlation among them.RESULTS:1. In 18 cases,one has ecchymoma after operation(5.55﹪),there is not many complication, consistent with some literature records. 2. There are 16 cases that electrode in scala tympani,2 cases in scala vestibuli, the depth of electrode is 18.79±2.36mm(degree of accuracy 0.1㎜),the distance between electrode and cochlear axis(degree of accuracy 0.1㎜).3. Comparing the depth of electrode between scala tympani and scala vestibuli, the average depth in scala tympani group is 18.97±2.39mm, the average depth in scala vestibuli is 17.33±2.02mm.4. Comparing the depth of electrode between the different types by t test, the average depth of curved electrodes group is 17.55±1.23mm, the average depth of straight electrodes group is 18.03±1.75mm,there is not statistically significant(t=0.569 ,p=0.580>0.05).5. Comparing the average threshold between the curved electrodes group and the straight electrodes group of COCHLEAR corporation,the average depth of straight electrodes group is 190.68±18.20CL, the average depth of curved electrodes group is 171.17±8.11CL, there is statistically significant(t=-2.432,P=0.032<0.05).6. Grouped by age, compare the diversity of average threshold among the different age groups with t test and analysis of variance. The average threshold of 3-year-old group is 178.34±14.54CL,of 3-year-old to 6-year-old group is 179.05±6.22CL,of 6-year-old group is 195.47±33.55CL, there is not statistically significant(F=0.066,P=0.936>0.05).7. Comparing the average threshold between the scala tympani group and scala vestibuli group, the average threshold of scala tympani group is 181.45±18.72CL,the average threshold of scala vestibuli group is 187.50±5.94CL.8. Analyzing the depth of electrode implanted and the average threshold of ECAP, we find that there is negative correlation between them(r=0.639,p=0.014<0.05).9. Analyzing the distance of electrode to modiolar and the electrode's ECAP, we find that there is positive correlation between them(r=0.672, p=0.008<0.05).CONCLUSION: The plain scan and three-dimensional reconstruction of the 64-slice spiral CT scan can display the bony spiral lamina clearly, so it can distinguish the position of electrode, the three-dimensional contour reconstruction can measure the depth of electrode that implanted in cochlea and the distance between electrode and modiolar ; the distance between electrode and modiolar is positive with threshold of ECAP, the distance is more nearer, the threshold of ECAP is more lower; the depth of electrode implanted is negative with the average threshold of ECAP, the depth is more longer, the threshold of ECAP is more lower .