Correlation of high-resolution computed tomography and gross anatomic sections of the temporal bone: Part I. The facial nerve

Detailed anatomic analysis of the human temporal bone has been made possible by correlating high-resolution computed tomography (CT) with gross anatomic sections. Serial CT scans of isolated temporal bones were obtained in the transaxial (horizontal), coronal, and sagittal planes at 1.5-mm intervals. The temporal bone was sectioned at 2.0-mm intervals in planes parallel to the CT scans. Based on a correlation of these sections, the facial nerve canal was divided into four segments and the planes in which each is best observed are described and illustrated. The first segment in the internal auditory canal is best visualized in the sagittal plane, the labyrinthine segment and geniculate ganglion in the coronal and transaxial planes, the tympanic portion in the sagittal plane, the genu, between the tympanic and mastoid portion, in the sagittal plane, and the mastoid portion and the stylomastoid foramen in the coronal and sagittal planes.     

Correlation of high resolution computed tomography and gross anatomic sections of the temporal bone. Part III. Cochlear and vestibular aqueducts

Gross anatomic sections of isolated temporal bones (TB) were compared with high resolution computed tomography (CT) scans obtained utilizing contiguous 1.5-mm thick slices in the transaxial, coronal, and sagittal planes. Each TB was then sectioned at 2.0-mm intervals in planes parallel to those of the CT scans. Both the cochlear and vestibular aqueducts were best visualized in the coronal plane; the transaxial plane proved less reliable and the sagittal plane was not useful at all. The cochlear aqueduct in the coronal plane appears as a funnel-shaped configuration with its widest portion opening into the subarachnoid space. The vestibular aqueduct at its opening into the epidural space is well visualized in the coronal plane, and as it traverses the bone toward the vestibule it appears as an oval to spherical lucency, whereas in transaxial sections it is seen as a small longitudinal lucency.     

Anatomy of sinus tympani

30 temporal bones from adult cadavers of both sexes were examined. After the tympanic sinus was identified, its morphologic features were evaluated. Minimum distance from adjacent structures: lateral and posterior semicircular canal, facial nerve canal and jugular fossa were taken. Measurements were taken under operative microscope with eye-piece graduation of 0.05 mm accuracy. Four main morphologic types of entrance to the sinus and two main developmental forms--deep and shallow sinus were distinguished. Deep sinus coexisted with absence of bridge and conversely if bridge was seen sinus was shallow. Deep sinuses were located close to the facial canal, in some cases penetrating around the canal up to 2/3 of canal's circumference. This anatomical variation increase the risk of the facial nerve damage during the surgery. In most of cases tympanic sinus is oval in shape. It's long diameter lies in vertical plane. The mean distance between the sinus and adjacent structures were as following: facial nerve canal--1.5 mm, lateral semicircular canal--2.1 mm, posterior semicircular canal--1.59 mm, jugular fossa--5.5 mm. No differences dependent from gender and side were found.     

基于CT的前庭蜗器断层解剖研究

目的从形态学角度阐述前庭蜗器断层解剖的微细结构,为人工耳蜗植入术和相关工作提供参考.方法采用火棉胶切片制作法,分水平位和冠状位切片并与CT断层扫描方位一致,选择代表性层面进行观察描述.水平位自下而上分蜗窗龛、蜗窗、锤骨柄、锤骨颈、锥隆起、面神经鼓室段、面神经膝、外半规管等8个层面描述;冠状位自前向后分耳蜗、前庭窗、蜗窗、面神经乳突段等4个层面描述.结果观察前庭蜗器各断层解剖的微细结构,并将火棉胶切片与CT扫描图像相对照,显示面神经迷路段终段、面神经膝和面神经鼓室段起始部与耳蜗中间周、基底周关系密切,将水平位切片与冠状位切片相结合,可全面显示面神经与耳蜗的位置关系,经比较水平位切片更具优势.冠状位切片可清晰的显示出蜗窗龛和蜗窗的解剖结构.结论通过分析研究面神经与耳蜗的位置关系以及蜗窗龛和蜗窗的解剖结构,对避免人工耳蜗植入术中对面神经的损伤和耳蜗钻孔位置定位及电极插入等都具有极大的帮助.     

面神经鼓乳段定位及术中面瘫预防

目的:根据颞骨解剖结合中耳手术体会,探讨面神经走行定位,避免中耳手术中面神经损伤.方法:用30侧颞骨标本,模拟面神经减压术的手术步骤暴露面神经鼓乳段,确定面神经走行,用易见且恒定的标志进行面神经定位.结果:面神经水平段位于水平半规管与镫骨之间达匙突前上;垂直段位于鼓室后壁,垂直段后缘延长线与水平半规管后1/3相交,夹角为(117.04±2.42)°,其深度位于水平半规管及鼓环平面以下;外膝位于水平半规管前下方.水平半规管中点至面神经最短距离为(1.97±0.53)mm,砧骨短脚至面神经最短距离为(1.03±0.29)mm,匙突至面神经最短距离为(0.93±0.25)mm,镫骨头至面神经最短距离为(1.18±0.42)mm,前庭窗平面鼓沟至面神经的距离为(3.08±0.28)mm,圆窗平面鼓沟与面神经的距离为(2.13±0.34)mm.结论:水平半规管凸、砧骨短脚、镫骨、鼓环及匙突,是面神经鼓乳段理想的定位标志.熟悉面神经走行,可提高中耳手术安全性.     

Surgical anatomy of the facial nerve in Chinese mastoids.

Since racial differences in mastoid morphology exist, there may be racial differences in the surgical anatomy of the facial nerve in the mastoid. Thirty Chinese adult temporal bones were dissected. The facial nerve in the mastoid coursed vertically (60.0%), anteriorly (33.3%) and posteriorly (6.7%) in the sagittal plane. In the coronal plane, it coursed vertically (46.7%) and laterally (53.3%). The chorda tympani was found to have extratemporal origin in 53.3% and for the rest, the distance of its origin from the stylomastoid foramen averaged 3.17 mm (range 0.5-6.0 mm). The mean dimension of the extended facial recess was 4.40 mm (range 3.0-6.0 mm). The facial nerve was at a mean of 3.15 mm (range 2.0-5.0 mm) posterior to the most posterior point of the tympanic annulus and partially crossed the tympanic annulus from medial to lateral at this point. In conclusion, the typical surgical anatomy of the mastoid facial nerve as described in the Western literature may not apply to the Chinese.     

Relationship of the facial nerve to the tympanic annulus: a direct anatomic examination.

OBJECTIVE: To examine the relation of the facial nerve to the only identifiable surgical landmark in the external auditory canal. INSTITUTION: Community-based teaching hospital. STUDY DESIGN: Examination of formalin-fixed human temporal bones. BACKGROUND: The transcanal approach is often used in tympanoplasty, canaloplasty, hypotympanotomy, and removal of tumors of the external auditory canal (EAC), such as exostoses and osteomas. Surgery of the EAC places the facial nerve at risk for injury as the nerve courses vertically in the posterior canal wall. Few articles have described the relation of the facial nerve's course to the tympanic annulus, the only identifiable landmark in the EAC. This study is the first to document the relationship of the course of the facial nerve with respect to the tympanic annulus by direct anatomic measurement of the temporal bone. METHODS: Thirty-seven formalin-fixed cadaver temporal bones were studied after skeletonization of the facial nerve and tympanic annulus. RESULTS: The facial nerve coursed lateral to the plane of the annulus in 70% of specimens, always in the posteroinferior quadrant. The nerve also coursed anterior to a plane through the most posterior point of the annulus in 73.1% of specimens, also exclusively in the posteroinferior quadrant. The course of the nerve was quite variable with respect to the annulus. CONCLUSIONS: The facial nerve is most vulnerable to injury in the posteroinferior quadrant in transcanal surgery. The annulus is not a reliable landmark for the facial nerve. Anecdotal evidence is cited and recommendations are offered.     

Temporal bone measurements on high-resolution computed tomography

The distances between the important neural and vascular structures in normal temporal bones were measured by using high-resolution computed tomography (HRCT). We examined 100 normal ears in 50 subjects ranging in age from 15 to 72 years (mean age 39 years). We measured the distances from the medial lip of the posterior wall of the internal auditory canal to the medial wall of the vestibule (mean 9.7 mm), from the cochlea to the tympanic segment of the facial canal (mean 1.76 mm), from the medial wall of the vestibule to the lateral aspect of the lateral semicircular canal (mean 8.03 mm), and from the external auditory canal to the lateral sinus (mean 13.2 mm). HRCT examination is the best method for defining the morphology of temporal bone.     

Transmastoid exposure of the labyrinthine segment of the facial nerve: an anatomical study

IntroductionCompression of the labyrinthine segment of the facial nerve by edema has been considered as an important pathology in the majority of the cases of idiopathic facial nerve paralysis. Hence, it is suggested that total decompression of the facial nerve should also include the labyrinthine segment by a middle fossa approach. However, the middle fossa approach requires craniotomy and temporal lobe retraction, which increases the morbidity. The labyrinthine segment of the facial nerve can also be reached through mastoidectomy. However, many ear surgeons are not familiar with this approach due to the lack of anatomical data on this surgical area.ObjectiveTo study the anatomical limitations of decompression of the labyrinthine segment via transmastoid approach.MethodsComplete mastoidectomy was performed in six adult cadavers heads. Dissection was extended in the zygomatic root and posterior bony wall of the external auditory canal to visualize the incudomallear joint completely. The bone between tympanic segment, lateral and superior semicircular canal’s ampullas and middle fossa dural plate was removed. Fine dissection was carried out over tympanic segment of the facial nerve in an anterosuperomedial direction the labyrinthine segment was reached.ResultsAll the mastoids were well pneumatized. Distances between the labyrinthine segment and middle fossa dura, and between the labyrinthine segment and superior semicircular canal, were 2.5 and 4.5 mm on average, respectively. In addition, distances between the middle fossa dura and dome of the lateral semicircular canal, and between the middle fossa dura and tympanic segment were 4.6 mm and 4.3 mm on average, respectively.ConclusionIt is possible to expose the labyrinthine segment of the facial nerve through mastoidectomy by dissecting the bone in the area between the tympanic segment of the facial nerve, middle fossa dural plate and ampullary ends of the lateral and superior semicircular canals.     

Oval window canal and CT-diagnosis of peripheral pareses of the facial nerve

Computed tomography (CT) has examined 200 patients (400 temporal bones) at the age of 0-74 with unaffected facial nerve and 28 patients with symptoms of peripheral paresis or paralysis of the facial nerve of different genesis. Polyposition CT of the temporal bone is an intravital noninvasive method of the Fallopius' canal visualization. The canal is visualized on the tomograms in 100% cases irrespective of the patients' age. The following causes of n. facialis paresis were revealed: neurinoma of the facial nerve, sarcoma of the temporal bone, destruction of the tympanic canal wall in chronic otitis media, fractures of the temporal bone, malformations of the Fallopius' canal in malformations of the temporal bone, stenosis of the canal in fibrous dysplasia. The above alterations of n. facialis canal determine further therapeutic policy.     

Use of reconstructed sagittal computed tomography images to plan middle cranial fossa surgery.

OBJECTIVE: To facilitate planning in temporal bone surgery for the middle cranial fossa approach by using sagittal reconstructed temporal bone computed tomography images. STUDY DESIGN: Comparison of anatomic measurements on random high-resolution, reformatted computed tomography scans of the temporal bone. METHODS: High-resolution computed tomography of 10 normal temporal bones in the axial and coronal planes was obtained, and two-dimensional sagittal reconstructions were performed using a commercial software program. Eight anatomical relationships between neural and/or vascular structures were measured. Representative images were inverted to recreate the plane of the middle cranial fossa approach. RESULTS: Anatomical relationships among the vestibule, superior semicircular canal, internal auditory canal, internal carotid artery, and middle cranial fossa exhibited a high SD in the 10 subjects. The sample size and the large range for the eight anatomical relationships precluded the detection of a significant difference between right and left temporal bones or sex and age of the patient. CONCLUSION: The present report presents a novel, practical measurement protocol for rapidly evaluating important individual anatomical differences in patients before middle cranial fossa surgery. Inverted sagittal reconstructions facilitate presurgical planning for the middle cranial fossa approach by 1) assessing critical anatomical relationships before surgery and 2) providing customized measurements between vital landmarks and the first in vivo measurements. This decreases the likelihood of surgical mishaps and improves teaching by providing the first in vivo measurements of practical anatomical relationships in the sagittal plane.     

Anatomical variations and relations of the medical and lateral portions of the attic and their surgical significance

The medial and lateral attics were examined in 150 specimens of temporal bones of adults using anatomical and histological methods. The medial attic varies in shape and size, depending upon the position of the auditory ossicles, the degree of prominence of the lateral semicircular canal and the direction in which the tympanic segment of the facial canal extends. The latero-medical diameter of this attic at the level of the body of the incus averages 1.7 mm., but is somewhat smaller at the level of the head of the malleus. The medial attic always communicates with the mesotympanum through an opening between the prominence of the tympanic part of the facial canal and the superstructures of the auditory ossicles. The lateral attic is always of smaller dimensions than the medial attic and its latero-medial diameter averages less than 1 mm. This attic very seldom communicates with the mesotympanum.     

中耳手术相关面神经管的解剖观测

目的：为避免中耳手术中对面神经的损伤。方法：对２０ 具（４０ 侧）成人尸头颞骨内面神经进行解剖观察。结果：①面神经裂缺率为３２．５％ （１３／４０）,迷路段、水平段、垂直段分别为５％ （２／４０）、２７．５％ （１１／４０）、７．５％ （３／４０）。②面神经垂直段与后半规管最短距离为０．６２～５．０８（２．４８±０．６３）ｍ ｍ ,鼓沟底水平面神经与鼓索神经最短距离为０～４．６２（２．１２±０．７６）ｍ ｍ ,鼓沟底水平面神经与鼓沟最短距离为２．９６～８．８２（５．８６±１．６２）ｍ ｍ 。③面神经水平段与外半规管最短距离为０～３．０２（１．９２±０．８４）ｍ ｍ ,与蹬骨底板最短距离为０．９２～４．０６（２．１４±０．９０）ｍ ｍ 。结论：熟悉颞骨内面神经解剖,可避免对面神经的损伤,减少和避免面瘫的发生     

颞骨CT三维重建面神经立体解剖定位

目的:探讨基于PC机的颞骨CT三维重建在面神经解剖定位中的方法和应用价值,总结出一套量化的研究面神经定位的方法,以便指导耳科及侧颅底手术。方法:使用3D-DOCTOR软件对成人轴位CT影像进行三维重建,显示颞骨内各重要结构的形态及其相互间复杂的立体关系。并用软件自带的功能测量面神经及其毗邻结构之间的距离和相对角度。分析测得的数据,总结面神经与其毗邻解剖标志结构之间的相对关系。结果:重建获得清晰的三维图像,包括面神经、鼓环、听小骨、匙突、锥隆起、内听道、耳蜗、半规管、颈静脉球窝、颈内动脉管等颞骨内结构。准确测量三维模型所得的面神经及其毗邻结构之间的相关参数并发现一定的规律性,这非常有益于手术中进行面神经快速定位和手术入路的设计。结论:基于PC机的颞骨CT三维重建可以准确地显示其内部各解剖结构及其相互间的空间立体关系,并可进行测量定位。     

Planer orientation of the bilateral semicircular canals in dizzy patients

Objective

Recent development of 3-dimensional analysis of eye movement enabled to detect the eye rotation axis, which is used to determine the responsible semicircular canal(s) in dizzy patients. Therefore, the knowledge of anatomical orientation of bilateral semicircular canals is essential, as all 6 canals influence the eye movements.

Subjects and methods

Employing the new head coordinate system suitable for MR imaging, we calculated the angles of semicircular canal planes of both ears in 11 dizzy patients who had normal caloric response in both ears.

Results

The angles between adjacent canal pairs were nearly perpendicular in both ears. The angle between the posterior canal planes and head sagittal plane was 51° and significantly larger the angle between the anterior canal planes and head sagittal plane, which was 35°. The angle between the horizontal canal plane and head sagittal plane was almost orthogonal. Pairs of contralateral synergistic canal planes were not parallel, forming 10° between right and left horizontal canal planes, 17° between right anterior and left posterior canal planes and 19° between the right posterior and left anterior canal planes.

Conclusion

Our measurement of the angles of adjacent canal pairs and the angle between each semicircular canal and head sagittal plane coincided with those of previous reports obtained from CT images and skull specimens. However, the angles between contralateral synergistic canal planes were more parallel than those of previous reports.     

中耳手术中的面神经定位

目的结合颞骨解剖和面神经手术，明确适用于手术的面神经解剖标志。方法44具颞骨标本面神经解剖，106例周围性面神经麻痹的面神经减压手术。根据面神经周围的固定解剖标志，确定面神经位置。结果①面神经垂直段标志：水平半规管后中1／3交界处垂直线提示面神经后缘；砧骨短角上缘弧度延长线为面神经垂直段前缘；面神经与水平半规管基本在同一深度；②面神经水平段标志：位于砧骨短突之下；在水平半规管隆突前缘向前上呈30。行走；在匙突后方，面神经与匙突平行形成中上鼓室内侧面交界缘；经过匙突面神经向前上行走到膝状神经节；③膝状神经节定位：从镫骨头到匙突等距离延长线为膝状神经节位置；④鼓索神经定位：鼓索从左侧鼓沟的3点或右侧鼓沟的9点出骨管，沿鼓沟向前行走于砧骨长突外侧和锤骨颈内侧；鼓索神经从面神经发出处距离茎乳孔5—8mm；鼓索位于鼓膜紧张部与松弛部交界处。所有手术所见面神经走向符合解剖所见。结论中耳乳突的固定标志是面神经定位的参照物，其中水平半规管的位置最恒定，根据参照物确定面神经位置提高了手术的安全性。     

Temporal bone findings in pierre robin syndrome

This is the first complete report on the histopathologic study of the temporal bones from an infant with a well-documented Pierre Robin syndrome (micrognathia, glossoptosis and cleft palate), demonstrating multiple middle and inner ear anomalies. The anomalies are basically architectural malformations rather than neural or end organ developmental anomalies. The anomalies in this case, except for a few points, are somewhat similar in both ears. Multiple anomalies include: abnormal narrowing of the cms commune-utricle junction, superiorly located cms commune and posterior semicircular canal, underdeveloped modiolus, absence of the bony septum between the middle and apical coil (existence of scala communis in left ear), abnormally small internal auditory meatus, and abnormal direction of internal auditory canal, large cartilaginous mass around the superior semicircular canal and in the tympanic end of the fissula ante fenestram, small facial nerve, large facial bony canal dehiscence, anomalic stapes, etc.     

成人面神经管螺旋CT曲面重建图像的解剖学研究

目的探讨螺旋CT曲面重建图像对面神经管解剖学研究的参考价值.方法对50例正常成人(100侧)面神经管进行螺旋CT曲面重建,描述正常成人面神经管曲面重建图像的解剖特征,并进行测量.结果 50例正常人的轴位和冠状位曲面重建图像,可在一幅图像上清晰显示双侧面神经管结构,显示率100%,矢状位曲面重建图像只能完整显示单侧面神经管结构;三个方位曲面重建图像上能较准确测得面神经管长径和宽径,测量值差异无显著性意义(P>0.05),而对弯曲部的显示、测量和对毗邻结构的显示,不同方位有各自价值和限度.结论螺旋CT面神经管曲面重建图像具有简便、实用、准确、直观等优点,是目前研究面神经管影像解剖的良好方法.对面瘫定位诊断具有重要指导意义.     

Adverse effects of semicircular circle angles variation on Epley repositioning procedure: a study on reconstruction of Micro-CT images 3D

Abstract

Background: For patients with posterior semicircular canal (PSC) BPPV, Epley re-position maneuver and some improvement methods are the most efficient treatment methods. But there were still 9.43% patients who were not benefit from Epley re-position maneuver.

Objective: To measure the angles of semicircular canals and evaluate its effect on Epley maneuver.

Methods: Fifteen skull specimens, containing 30 temporal bone specimens were included. After Micro-CT scanning, 3D reconstruction was loaded with the CT image. The angles between each semicircular canal and each standard skull plane were measured. Furthermore, the angles’ effect on Epley maneuver was evaluated according to the three-dimension (3D) model.

Results: Angles of PSC plane: Frankfurt plane was 71.54?±?6.51, sagittal plane was 53.77?±?5.36°, and the coronal plane was 43.33?±?3.56°. Angles between PSC and the sagittal plane of skulls had an adverse effect on Epley maneuver, when it was less than 45°.

Conclusion: 1. Variation could be found in angles between the semicircular canals and the standard planes of skulls, which meant variation of semicircular canals’ location existing in skulls. 2. The variation of angles between PSC and sagittal plane could have an adverse effect on the Epley maneuver when the angle was less than 45°, which may cause the Epley maneuver to be invalid.