| Objectives Compared with microscopy,the application of en doscopy in the middle ear cavity is becoming more and more mature.In recent years,the application of endoscopy in the inner ear,lateral skull base and other delicate and complex parts,especially involving the lesions related to the lateral skull base,has been reported sporadically abroad in recent years,while the clinical application of endoscopy in the lateral skull base in China is less.For otolaryngologist,lateral skull base surgery is challenging in terms of understanding,visualization and oper ation because of its complex anatomical structure.The purpose of this study was to explore the surgical approach of the endoscopic transcanal infracochlear approach for resection to petrous Apex,to observe the important anatomical landmarks of the middle ear under endoscope,especially the anatomy around the round window,to find the anatomical landmarks for locating the infracochlear corridor,and to quantify the infracochlear corridor under the three-dimensional reconstruction of high-resolution temporal bone CT,so as to provide a constant anatomical landmark and imaging basis for the surgical approach.Materials 10 fresh frozen cadaveric heads(20 sides),including 4 adult specimens perfused with red latex through common carotid artery,4 male temporal bone specimens(8 ears)and 6 female temporal bone specimens(12 ears).The skull was intact,there was no middle ear deformity(confirmed by research),and there was no record of origin and age.All cadavers were provided by the Department of Human Anatomy,Medical College of Shenzhen University.Laboratory instruments and equipment endoscopy system: using STORZ 0,30,70 degrees,15 cm long and 3mm diameter endoscopy and ultra-high definition endoscopy system,medtronic force power system and otology endoscopy drill(1-3mm diameter)and STORZ otology microsurgery instruments,surgical instruments include: circumcision knife,longitudinal cutting knife,curette,peeler,crocodile forceps,hammer scissors,microcup forceps,otology endoscopy grinding drill,electric attractor,etc.Methods1.Application with 10(20 sides)fresh frozen adult cadavers head,simulating endoscopic transcanal infracochlear approach for resection of petrous Apex,Preoperative temporal bone CT was used to measure the vertical distance between the basal turn of the cochlea and the angle between internal carotid artery and jugular bulb,as well as the distance between the cochlea base and jugular vein bulb.To observe the important anatomical landmarks of the middle ear under endoscopy,especially the anatomy around the round window,and find the anatomical markers for locating the infracochlear corridor(lower border of promontory,internal carotid artery canal,jugular bulb,finiculus,fustis),and to provide the invariable anatomical markers and imaging basis for the surgical approach.2.Retrospective analysis of high resolution computed tomography(HRCT)of temporal bone in 85 patients(170 sides)was made.Imaging features of infracochlear corridor and petrous apex air chamber in 85 patients(170 sides)were recorded.CT typing of subcochlear passage and petrous apex air chamber of temporal bone was summarized.According to the relationship between the columnar bone,the foot of the apex and the anterior inferior tympanic sinus adjacent to the circular window,the gasification degree of infracochlear corridor and petrous apex air chamber was divided into types A,B and C.3.Statistical processing: All measurements were averaged three times,and all measurements were analyzed by SPSS 23.0 software.The main statistical methods included descriptive statistical analysis,T-test and variance analysis.The test level was 0.05,P < 0.05,which had statistical significance.The results were expressed as mean + standard deviation.Results1.Three-dimensional reconstruction of high-resolution CT of temporal bone was performed before endoscopic petrous apex pneumonectomy via infracochlear approach of external auditory meatus in 10 temporal bone specimens(2 0 sides).The vertical distance between the basal turn of the cochlea and the angle between internal carotid artery and jugular bulb was(6.46±1.02)mm,and the distances from the basal turn of the cochlea to the jugular bulb was(3.67±0.58)mm(p=0.000 < 0.001),which has statistical significance.In which,the vertical distance between the basal turn of the cochlea and the angle between internal carotid artery and jugular bulb: the pneumatized petrous apex was(6.79±0.60)mm,the non-pneumatised was(6.28±1.17)mm(p = 0.15 > 0.05,with no statistical significance);the distances from the basal turn of the cochlea to the jugular bulb: the pneumatized petrous apex was(4.06±0.36)mm and the non-pneumatised was(3.45±0.58)mm.(p = 0.01 < 0.05).(Statistical data were analyzed by SPSS 23.0.)2.Temporal bone CT measurements were made in 85 clinical samples(170 ears),including 50 males and 35 females,with an average age of 39.96 years: the vertical distance between the basal turn of the cochlea and the angle between internal carotid artery and jugular bulb was(6.83±1.50)mm;the distances from the basal turn of the cochlea to the jugular bulb was(3.82±1.29)mm(p=0.000 < 0.001),with statistical significance.The vertical distance between the basal turn of the cochlea and the angle between internal carotid artery and jugular bulb: the pneumatized petrous apex was(7.19±1.44)mm,the non-pneumatised was(6.68±1.50)mm(p = 0.019 < 0.05,with statistical significance);the distances from the basal turn of the cochlea to the jugular bulb: the pneumatized petrous apex was(4.06±1.42)mm and the non-pneumatised was(3.74±1.22)mm(p = 0.06 > 0.05,without statistical significance).(Statistical data were analyzed by SPSS 23.0.)3.CT classification of infracochlear corridor and petrous apex of temporal bone: Type A pneumatised type 31.18%(53 ears),Type B,marrow type 57.65%(98 ears),Type C sclerosed type 11.18%(19 ears).4.20 frozen adult cadaveric heads were simulated by endoscopic transcanal infracochlear approach for resection of petrous apex.The infracochlear corridor was located between the internal carotid artery,the jugular bulb and the triangular area surrounded by the promontory.A infracochlear corridor was observed between finiculus and fustis.The vertical segment of the internal carotid artery was located at the front of the anatomical area and the jugular bulb and ear were ground with a diamond drill.In the lateral wall of the tympanic chamber between the cochlear base ro tation,such as the lower part of the bony promontory,the petrous apex gas chamber can be seen in well gasified specimens.Among them,8 cases of gasified petrous apex,5 cases of jugular bulb,19 cases of petrous apex gas chamber were successfully resect ed,and 1 case of petrous apex gas chamber was difficult to complete through infracochlear corridor because of the obvious high position of jugular bulb.ConclusionsIn endoscopic transcanal infracochlear approach for resection to petrous apex,the finiculus and fustis can be used as important anatomical markers for locating the infracochlear corridor.The triangular area surrounded by internal carotid artery,jugular bulb and promontory can be used as a constant anatomical marker for the infracochlear corridor.High resolution temporal CT scan should be an important reference before the operation.From the angle of anatomy,endoscopic resecti on of petrous apex lesions via infracochlear approach of external auditory canal is feasible.It can avoid damage to internal auditory canal,cochlea and labyrinth,and preserve hearing.It can be used as one of the important surgical methods for the treatment of petrous apex lesions.The relevant data of this study provide theoretical reference for avoiding the dama ge of cochlea and labyrinth and locating the infracochlear corridor accurately in endoscopic transcanal infracochlear approach for resection to petrous apex. |
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