颅中窝入路听神经瘤手术相关解剖标志的三维成像研究

目的利用多层螺旋CT扫描三维成像（3 D-CT）技术研究颅中窝入路听神经瘤手术时上半规管与弓状隆起之间的相互解剖关系,评价3 D-CT对颅中窝听神经瘤手术方式选择的有效性。方法选取1 4例干颅和7例1 0%甲醛固定的成人头颅标本进行颞骨部位的多层螺旋CT扫描,利用AW4.1工作站对上半规管和弓状隆起解剖关系进行测量。结果3 D-CT可以清晰显示颅中窝及岩骨重要的解剖标志,上半规管和弓状隆起二者间的空间关系并非完全一致。结论弓状隆起并非是判断上半规管最精确的标志点,术前通过3 D-CT可以清晰显示上半规管与弓状隆起二者的空间位置关系,以指导术中避免损伤上半规管及准确定位内听道,通过术前3 D-CT可以达到个体化治疗的目的。     

A study of middle cranial fossa anatomy and anatomic variations

We conducted a study to establish standardized measurements of the common anatomic landmarks used during surgery via the middle cranial fossa approach. Results were based on high-resolution computed tomography (CT) images of 98 temporal bones in 54 consecutively presenting patients. Measurements were obtained with the assistance of the standard PACS (picture archiving and communication system) software. We found that the superior semicircular canal (SSC) dome was not the highest point on the temporal bone (i.e., the arcuate eminence) in 78 of the temporal bone images (79.6%). Pneumatization above the SSC and above the internal auditory canal (IAC) was found in 27 (27.6%) and 39 (39.8%) temporal bone images, respectively. The anterior wall of the external auditory canal was always anterior to the anterior wall of the IAC. The mean angles between the SSC and the posterior and anterior walls of the IAC were 42.3 degrees and 60.8 degrees, respectively. We also measured other distances, and we compared our findings with those published by others. We hope that the results of our study will help surgeons safely and rapidly locate anatomic landmarks when performing surgery via the middle cranial fossa approach.     

Petrous anatomy for middle fossa approach

OBJECTIVE: The objective was to describe the relationship of anatomical landmarks required for the middle fossa approach to lesions of the petrous apex and internal auditory canal (IAC). Landmarks for safe identification of the IAC are defined, as are two zones (safe zones I and II) anterior and posterior to the IAC. STUDY DESIGN: Temporal bone anatomical study. METHODS: Ten temporal bones underwent high-resolution computed tomography followed by wet bench dissection. A set of 39 different distances between vital structures was measured, where possible, from both radiology films and under the microscope. Mean, median, minimum, and maximum measurements of all distances were determined. Angular measurements were made using a specially designed instrument. RESULTS: Measurements were made in an anatomical position to mimic the middle fossa surgical technique. Measurements are presented for the superior surface of the temporal bone from the sigmoid sinus and inner table to vital structures, from the anterior and posterior petrous apex, and from the IAC. CONCLUSIONS: Petrous apex anatomical knowledge is required for the safe middle fossa approach to the IAC and petrous apex. Two safe zones are defined that should prevent damage to the cochlea and the superior semicircular canal.     

Cochlear implantation trough the middle cranial fossa: a novel approach to access the basal turn of the cochlea

The classic approach for cochlear implant surgery includes mastoidectomy and posterior tympanotomy. The middle cranial fossa approach is a proven alternative, but it has been used only sporadically and inconsistently in cochlear implantation.ObjectiveTo describe a new approach to expose the basal turn of the cochlea in cochlear implant surgery through the middle cranial fossa.MethodFifty temporal bones were dissected in this anatomic study of the temporal bone. Cochleostomies were performed through the middle cranial fossa approach in the most superficial portion of the basal turn of the cochlea, using the meatal plane and the superior petrous sinus as landmarks. The lateral wall of the internal acoustic canal was dissected after the petrous apex had been drilled and stripped. The dissected wall of the inner acoustic canal was followed longitudinally to the cochleostomy.ResultsOnly the superficial portion of the basal turn of the cochlea was opened in the fifty temporal bones included in this study. The exposure of the basal turn of the cochlea allowed the visualization of the scala tympani and the scala vestibuli, which enabled the array to be easily inserted through the scala tympani.ConclusionThe proposed approach is simple to use and provides sufficient exposure of the basal turn of the cochlea.     

Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey

OBJECTIVE: To determine the incidence and etiology of dehiscences of bone overlying the superior semicircular canal in a temporal bone archive. DESIGN: A microscopic study was performed of 1000 temporal bones from 596 adults in a university hospital registry. Specimens were sectioned vertically in the plane of the superior semicircular canal. Measurements of minimum bone thickness over the superior canal were made in a subset of 108 randomly chosen specimens. All bones were examined for thinning or dehiscence relative to these norms. Clinical histories, when available, were reviewed. RESULTS: Complete dehiscence of the superior canal was identified in 5 specimens (0.5%), at the middle fossa floor (n = 1) and where the superior petrosal sinus was in contact with the canal (n = 4). In 14 other specimens (1.4%), the bone at the middle fossa floor (n = 8) or superior petrosal sinus (n = 6) was no thicker than 0.1 mm, significantly less than values measured in the control specimens (P<.001). Abnormalities were typically bilateral. Specimens from infants demonstrated uniformly thin bone over the superior canal in the middle fossa at birth, with gradual thickening until 3 years of age. CONCLUSIONS: Dehiscence of bone overlying the superior canal occurred in approximately 0.5% of temporal bone specimens (0.7% of individuals). In an additional 1.4% of specimens (1.3% of individuals), the bone was markedly thin (< or =0.1 mm), such that it might appear dehiscent even on ultra-high-resolution computed tomography of the temporal bone. Sites affected were in the middle fossa floor or a deep groove for the superior petrosal sinus, often bilaterally. These abnormalities may arise from failure of postnatal bone development. Thin areas of bone over the superior canal may be predisposed to disruption by trauma.     

Cranial thickness in superior canal dehiscence syndrome: implications for canal resurfacing surgery.

OBJECTIVE: To use morphometric analyses of cranial thickness to investigate 2 cases of unanticipated calvarial bone resorption in superior canal dehiscence (SCD) resurfacing surgery. DESIGN: Retrospective morphometric analysis of high-resolution computed tomography (CT) temporal bone scans in normal and control subjects with accompanying case reports. SETTING: Tertiary care referral center. PATIENTS: Two patients with SCD and failed resurfacing because of bone resorption. Temporal bone CT scans from 30 sex-matched controls. INTERVENTION: Resurfacing of SCD via a middle fossa approach using a split thickness calvarial graft from the craniotomy site. MAIN OUTCOME MEASURE: Mean cross-sectional area of the middle fossa craniotomy bone flap and mean cranial thickness at 30 and 45 degrees above the middle fossa floor. RESULTS: Two patients had delayed failure of SCD resurfacing surgery as manifested by return of symptoms. High-resolution CT scans in both, and intraoperative confirmation in one, confirmed resorption of the bone graft. Measurements of cross-sectional area of the middle fossa craniotomy on high-resolution CT scans demonstrated significantly reduced values in the two SCD patients as compared with normal controls (Mann-Whitney U test, p<0.05). Cranial thickness outside the squamous temporal bone was reduced but did not reach statistical significance. CONCLUSION: Morphometric measurements of the calvarium have demonstrated that the squamous temporal bone is thinner in patients with SCD as compared with controls. Thus, the process leading to defects in the tegmen extends beyond the petrous pyramid. This suggests that there may be extratemporal factors leading to the development of a dehiscence. These findings also have implications for the surgical treatment of this disorder. Resurfacing methods may have a higher failure rate as the bone graft has reduced mass and maybe prone to resorption. Canal plugging methods may provide a more definitive means of addressing the dehiscent labyrinth than resurfacing.     

New method of identifying the internal auditory canal as seen from the middle cranial fossa approach

OBJECTIVES: The middle cranial fossa approach allows one to remove acoustic tumors and preserve the facial nerve and hearing. However, there are no consistent landmarks on the surface of the temporal bone to identify the internal auditory canal. This study was designed to identify the internal auditory canal by use of external and internal references as seen during the middle cranial fossa approach. METHODS: We dissected 32 temporal bones using the middle cranial fossa approach and measured the distances from the posterior origin of the zygomatic arch to an imaginary coronal line between the foramen spinosum and the foramen ovale. We measured the angle between the lines drawn from the posterior origin of the zygomatic root to the foramen spinosum and from the foramen spinosum to the porus of the internal auditory canal. RESULTS: The distances were 14.7 mm and 22.9 mm, respectively, and the angle was roughly 90 degrees. CONCLUSIONS: In this study, we found external and internal landmarks that help to locate the internal auditory canal.     

Otogenic Pneumocephalus Associated with a Ventriculoperitoneal Shunt

Otogenic pneumocephalus is a condition of intracranial air originating from the middle ear or mastoid air cells. This communication between the intracranial cavity and the pneumatic cavities is usually associated with trauma after cranial fractures or iatrogenic trauma. We present a rare case of otogenic pneumocephalus arising in the left posterior fossa from wellpneumatized mastoid air cells. The patient complained of roaring tinnitus that developed 29 months after ventriculoperitoneal shunt insertion due to brain tumor surgery. High resolution computed tomography scan of the temporal bones revealed a large pneumocephalus below the left tentorium, and a bony dehiscent route was clearly identified in a sagittal view. A left mastoidectomy with preservation of the posterior wall of the external auditory canal was performed, and the expected bony dehiscent site was identified in the posterior fossa dura plate, just posterior to the posterior semicircular canal, below the Donaldson''s line. This communication was sealed with a temporalis muscle plug from the deep temporalis muscle fascia and bone dust. Pneumocephalus may be caused by negative intracranial pressure in a patient with very well-pneumatized mastoid bone, and it can be a possible cause of ''wind-like'' sound in the ear.     

Use of reconstructed,non-orthogonal plane,high-resolution computed tomography of the temporal bone in the planning of temporal bone surgery

OBJECTIVES: To demonstrate the utility of high-resolution computed tomography (HRCT) reconstructed in non-orthogonal planes in the planning of temporal bone surgery. STUDY DESIGN: Qualitative and quantitative comparison of in vivo anatomic measurements between orthogonal and non-orthogonal plane reformatted HRCT of the temporal bone. METHODS: HRCT data of 10 normal temporal bones were reconstructed two-dimensionally in two non-orthogonal planes. Parallel to the plane defined by the superior semicircular canal (defined as transverse) as well as perpendicular to the plane defined by the superior semicircular canal (defined as longitudinal). This was done using commercially available software. Sixteen surgically important relationships between neural, vascular and/or bony structures were measured and analyzed. RESULTS: Quantitatively, wide variations were obtained in the measurements obtained from images of both non-orthogonal planar orientations. These variations were not age or sex dependent. Qualitatively, the images obtained highlight the anatomy of the temporal bone and skull base as it will be encountered during otologic surgery, since the surgical visual axis is along the long axis of the temporal bone. CONCLUSIONS: The reformatted images in non-orthogonal planes were superior to the axial and coronal series because they condensed critical relationships into a single perspective which promoted an intuitive understanding of the surgical approach. These reconstructed images show wide differences in quantitative measurements between surgically relevant landmarks. The protocol can be easily implemented in the clinical setting and is a potentially valuable educational tool. We recommend that non-orthogonal reconstructed images be routinely included with orthogonal temporal bone HRCT scans.     

Transpetrosal approach: an anatomical study of temporal bone

Resection of the petrous temporal bone to various degrees provides different levels of access to lesions of the posterior fossa. However, regarding the numerous variations, precise distances of petrosal bone are not still clearly described. This may lead to serious complications during transpetrosal surgeries. Our objective was to evaluate different distances of temporal bone landmarks in order to assess their variations and the possible correlations between them. This anatomical study was performed on 60 temporal bones from 60 human cadavers in the years 2006 and 2007. All the bones contained an adequate portion of the petrous apex and attached fossa dura. Twelve landmarks were defined and 27 different distances were measured for each temporal bone using two-point caliper. Less variation was observed in the superoinferior diameter of horizontal carotid canal with the less coefficient of variation (CV) of 9.29; whereas, the most variation was detected in the inferior (axial) plane of posterior semicircular canal to superior plane of jugular bulb (CV = 57.65). There was a significant correlation between vertical intratemporal diameter of carotid in pyramidal direction, and superior–inferior diameter of horizontal carotid canal (r _Pearson = 0.500, P < 0.001). Other significant correlations were also found between other distances. The variations of different distances and landmarks were evaluated and many significant correlations were demonstrated between them which could potentially aid ENT specialists and neurosurgeons in order to approach anatomical landmarks and cranial fossas more safely during otologic and neurotologic surgeries. It could also help the design of middle ear prosthesis.     

Endolymphatic duct status during middle fossa dissection of the internal auditory canal: a human temporal bone radiographic study

OBJECTIVE: Successful hearing preservation after acoustic neuroma resection is sometimes complicated by delayed hearing deterioration. The middle fossa approach appears to offer superior long-term hearing results when compared to the retrosigmoid surgical approach. The goal of this study is to investigate the hypothesis that internal auditory canal (IAC) drilling during middle fossa acoustic neuroma removal is associated with a lower incidence of endolymphatic duct (ELD) injury, a potential cause of delayed hearing loss (HL) known to accompany retrosigmoid hearing preservation dissection techniques. STUDY DESIGN: A human temporal bone anatomic and radiographic study complemented with a literature review. METHODS: Twenty human temporal bones were analyzed with high-resolution multislice computed tomography (HRMCT) and subjected to standard extended middle fossa IAC dissection with labyrinthine preservation and follow-up HRMCT for analyses of the ELD. RESULTS: Zero of 20 (0%) temporal bones were found to have violation of the ELD with preservation of the labyrinthine structures and the endolymphatic sac. Reviews of human and animal studies indicate that injury to the ELD may create endolymphatic hydrops, a known cause of hearing deterioration. CONCLUSION: The ELD is not vulnerable to injury during IAC dissection using the middle fossa approach. A previous radiographic study has shown that the ELD is violated in 24% of temporal bones during retrosigmoid dissection of the IAC. These findings support and may help explain other outcome studies that show that long-term hearing results are superior with the use of the middle fossa approach when compared to results following retrosigmoid dissection.     

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.     

高分辨率CT颅中窝径路定位内耳道的解剖研究

目的 研究术前高分辨率CT (high resolution computerized tomography,HRCT)个体化测量,利用颧弓根、棘孔与锤骨头三者的距离关系经颅中窝径路定位内耳道及面神经的可行性.方法18例福尔马林固定的成人颞骨标本,分为A组10耳,B组8耳,常规行HRCT扫描后进行测量.A组行颅中窝径路手术,比较各解剖实测值与CT测量值之间的关系,建立CT数据模型.B组行颅中窝径路手术时在CT测量值辅助下以颧弓根、棘孔及锤骨头为标志物寻找内耳道.采用配对t检验分析两种方法在各解剖结构测量结果间的差异,以P＜0.05为差异有统计学意义.结果 A组中锤骨头与周围重要解剖结构距离的CT测量值与解剖实测值间结果差异无统计学意义(P值均＞0.05).在HRCT辅助下行颅中窝手术时,B组利用颧弓根到锤骨头及棘孔到锤骨头的CT测量距离指导手术,在1.5～3.7 mm范围内均可正确定位锤骨头;8耳中除1耳其内耳道-锤骨头连线与颧弓根-锤骨头参考线夹角为15°,余7耳颧弓根、锤骨头、内耳道均位于一条直线上.结论 颞骨HRCT可以较为真实地反映锤骨头与颧弓根、棘孔、内耳道等解剖结构之间的距离关系.在行颅中窝手术时,可以借助HRCT通过颧弓根及棘孔来定位锤骨头,进而在其他解剖标志点不清时利用锤骨头安全地定位内耳道.     

Cochleovestibular anomalies in children with cholesteatoma

OBJECTIVE: To describe the cochleovestibular apparatus on computed tomography (CT) imaging in patients with cholesteatoma. We asked whether cochleovestibular anomalies coexist in individuals with cholesteatoma. STUDY DESIGN: Randomized, controlled, prospective measurement. METHODS: A database search yielded 145 children with cholesteatoma: 31 met inclusion criteria by not having sensorineural hearing loss, not having an associated syndrome, and having digitally stored temporal bone CT imaging available. Prospective measurement of 31 individuals (62 ears) with unilateral cholesteatoma and 32 normally hearing nonsyndromic controls (64 ears) was performed by a neuroradiologist blinded to the study objective. Twenty-six temporal bone aspects on axial imaging were evaluated (16 measurement, 10 calculated from measurement). RESULTS: The cholesteatoma group had a larger endolymphatic fossa and vestibular aqueduct, and there was a trend for the lateral semicircular canal vestibule to be smaller as compared with controls. Subgroup analysis revealed a gradient in prevalence of these findings being most common in the congenital cholesteatoma group, intermediate in the acquired cholesteatoma group, and least common in controls. There were no differences in measurements between ears with cholesteatoma and contralateral disease-free temporal bones. CONCLUSIONS: Children with cholesteatoma have abnormal vestibular anatomy. The gradient in prevalence of these findings may suggest a relationship between congenital and acquired cholesteatoma. These may include a generalized temporal bone anomaly that predisposes to cholesteatoma formation, or a third variable such as genetic mutation may predispose to both anomalous cochleovestibular formation and cholesteatoma.     

Three-dimensional reconstruction of the temporal bone: Comparison of in situ,CT, and CBCT measurements

ObjectiveTo evaluate the accuracy of three-dimensional (3D) Cone Beam Computed Tomography (CBCT) and Computed Tomography (CT) reconstructions of human temporal bones compared with in situ measurements.Material and methodsExperimental anatomical study of 10 human temporal bones. Wilcoxon's test was used to compare 8 distances on each temporal bone measured in situ and then on 3D CT and CBCT reconstructions. Six landmarks were used: external auditory canal (EAC), tip of the mastoid process, tip of the occiput, zygoma, a point situated 1 cm above the tip of the mastoid process (T0) (open technique: lower limit of the mastoidectomy), head of stapes.ResultsNo significant difference was observed between the 3 measuring techniques for any of the distances studied (P > 0.05).DiscussionThis study demonstrates the equivalence of CBCT and CT for temporal bone measurements.ConclusionCBCT is a new imaging modality providing 3D reconstructions of the temporal bone that are as reliable as those obtained by CT. As a result of better spatial resolution compared to CT, CBCT is associated with a significantly lower radiation dose. This technique constitutes a morphological progress, as CBCT is comparable to CT, allowing investigation of pathological ears with a lower radiation dose.     

Transmastoid superior semicircular canal occlusion.

OBJECTIVE: The traditional surgical repair for superior semicircular canal dehiscence (SSCD) involves either canal plugging or resurfacing via the middle cranial fossa approach. We describe a novel transmastoid occlusion technique. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Three patients with symptomatic computed tomography-proven SSCD. INTERVENTION: Transmastoid superior semicircular canal occlusion using bone pate in 2 fenestrations, with 1 placed on either side of the dehiscence. MAIN OUTCOME MEASURES: Hearing and vestibular symptoms. RESULTS: Two patients were primary cases of SSCD, and a third patient had failed a previous middle fossa occlusion using fascia at an outside institution. In all 3 cases, the 2 sides of the superior semicircular canal adjacent to the dehiscence were occluded using bone pate, formed from a mix of bone dust and fibrin sealant. This allowed for a permanent bony partition to be achieved between the dehiscence and the remainder of the labyrinth. In all cases, hearing was either preserved or improved, and the procedure was successful in controlling vestibular symptoms. CONCLUSION: Transmastoid superior semicircular canal occlusion is a viable alternative to the customary middle fossa approach for superior canal dehiscence. Meticulous technique and the use of bone pate may help maximize auditory and vestibular results. Advantages of this technique include obviating a craniotomy, preclusion of temporal lobe retraction, familiarity of the approach for experienced otologists, and the ability to occlude the canal without manipulating the defect. The transmastoid approach for superior canal occlusion may not be possible when the dura is low hanging or when there is extensive cranial base dehiscence requiring reconstruction.     

Transtemporal supralabyrinthine approach]

Transtemporal supralabyrinthine approach is a modified middle cranial fossa approach. It offers all the advantages of a middle cranial fossa procedure and avoids its disadvantages, mainly the extensive temporal lobe retraction and frightening complications. The principle of the approach is to gain sufficient access toward the internal auditory canal by removing bone from the roof of the petrous pyramid rather than by elevating the middle fossa dura away from it. Fifteen patients underwent this approach for decompression of paralysed facial nerve resulted from temporal bone fracture, Bell's palsy and herpes zoster oticus; for removal of facial neuromas and primary cholesteatomas in temporal bone and for sectioning of great superficial petrous nerve. Preliminary study showed good results.     

Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study

Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge®) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT’s irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen’s reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.     

Anatomic relationships between surgical landmarks in type b and type c infratemporal fossa approaches

Anatomic relationships of the structures exposed in type B and C infratemporal fossa approaches were studied in 20 temporal bones. The intrapetrous carotid artery (ICA), cochlea (CH), eustachian tube (ET), foramen spinosum (FS), foramen ovale (FO) and anterior foramen lacerum (AFL) were exposed by drilling of the glenoid fossa and base of middle cranial fossa. The relationships of the ICA with the cochleariform process (CP), CH, ET, FS, FO and AFL were noted along with associated measurements. The CP was lodged at a mean distance of 9.2 mm from the ICA genu. The ET was found to intersect the ICA. The mean distance of the ICA to the CH was 1.6 mm. The carotid canal was dehiscent on its horizontal portion in 30% of the bones studied and on its vertical portion in 5%. The periarterial venous plexus was found in 70% of the bones. No obvious branch was observed emerging from the vertical portion of the ICA. The FS was found to be a canal having a mean length of 5.8 mm. Received: 14 March 1996 / Accepted: 22 August 1997     

The arcuate eminence is not a protrusion of the superior semi-circular canal but a trace of sulcus on the temporal lobe

Thirteen cadavers (26 temporal bones) were examined to show the arcuate eminence, especially its correspondence to the superior semicircular canal and inferior surface of the temporal lobe. Arc-like eminences on the petrous bone were observed in 92 per cent of specimens, however, they did not exactly correspond to the superior semi-circular canal. Some eminences corresponded to sulci of the temporal lobe of which most were traces of the occipitotemporal sulcus. On the other hand, a dull, smooth and even domed eminence existed in nine temporal bones independently of the arc-like eminence. Those eminences corresponded to each superior semi-circular canal in only three out of nine specimens. The arcuate eminence was listed as an important landmark in the middle cranial fossa approach. However, in order to drill out the internal auditory canal safety, surgeons should rely on other landmarks or apply other methods from our data.