部分迷路切除的应用解剖学观察及意义

目的探讨经部分迷路切除手术到达内听道和桥小脑角区的应用解剖及临床意义。方法对25个成人湿尸头经乳突分别切除上半规管和后半规管,再向深部削除岩部骨质,观察对岩尖、内听道及桥小脑角区暴露情况。结果选择性切除上半规管或／和后半规管的迷路部分切除术可到达岩尖和暴露部分内听道,不损及面神经和蜗神经,桥小脑角区显露改善。结论部分迷路切除人路可用于某些岩尖、桥小脑角或内听道占位病变的治疗。     

An anatomic and radiologic evaluation of access to the lateral internal auditory canal via the retrosigmoid approach and description of an internal labyrinthectomy.

OBJECTIVE: The retrosigmoid approach to the posterior petrous bone may be used as a hearing preservation operation for extirpation of posterior fossa and internal auditory canal (IAC) lesions. However, it is usually not possible to remove tumor from the most lateral portions of the IAC even after removing the retrolabyrinthine bone down to the posterior semicircular canal. Our goal was to examine the advantages and disadvantages of the retrosigmoid approach with respect to approaching the lateral IAC, to find what is gained by drilling down the retrolabyrinthine bone, and to describe an internal labyrinthectomy whereby the labyrinth is removed via a retrosigmoid approach. MATERIALS AND METHODS: Using a 3.5-cm craniotomy, a retrosigmoid approach was performed on one side in each of five whole fresh cadaveric heads. The IAC was identified, and the length of the IAC and the depth of the acoustic porus from the center of the craniotomy were measured. The bone posterior to the labyrinth was removed, and the length of the portion of the IAC still inaccessible was measured. These measurements were compared with measurements using computed tomography (CT) scans of each cadaveric head. Additionally, we present the findings of 11 patients who had an internal labyrinthectomy performed by the senior author. RESULTS: The average length of the IAC based on CT scanning was 11.2 mm (SD, 0.84 mm; range, 10-12 mm, 95% confidence interval [CI], 9.44-12.96). The potential gain predicted by the CT scans was 8.4 mm (SD, 0.9 mm; range, 7-9 mm). In the anatomic study, the average length of the IAC was 11.0 mm (SD, 2.3 mm; range, 8.0-13.0 mm; 95% CI, 9.26-12.78). The average length of the IAC that was inaccessible after removing the retrolabyrinthine bone was 6.7 mm (SD, 1.5 mm; range, 5.0-7.8 mm), or 61%. The average gain in access to the lateral IAC was 4.3 mm (SD, 1.0 mm; range, 2.7-5.2 mm). After performing an internal labyrinthectomy, the fundus was accessible, as was the labyrinthine segment of Cranial Nerve VII and the geniculate ganglion. CONCLUSION: The retrosigmoid approach provides access to the posterior petrous bone, and removal of the bone posterior to the labyrinth provides some additional access to the lateral IAC. However, an internal labyrinthectomy is necessary to provide access to the fundus of the IAC via the retrosigmoid approach.     

Effect on cochlear potentials of lateral semicircular canal destruction.

Recording of the cochlear potentials was successfully performed during experimental labyrinthectomy in the guinea pig and in three patients with acoustic neuromas during translabyrinthine removal of the tumors. In the guinea pig, complete interruption of the duct of the lateral semicircular canal including the endolymphatic canal caused little change in the endocochlear DC potential of the first cochlear turn and input-output function curve of the N1 component of the compound action potential elicited by 8-kHz tone bursts. Further drilling of the vestibular labyrinth in the guinea pig caused decline of these potentials when the vestibular was opened. In patients with acoustic neuromas, the interruption of the duct of the lateral semicircular canal hardly altered the N1 input-output function curve and N1 input-latency function curve during the 1-hour observation period. Consistent preservation of cochlear function even after interruption of lateral semicircular canals suggests the possibility of partial surgical labryrinthectomy with preservation of hearing for lesions involving semicircular canals.     

Extended middle fossa and retrolabyrinthine approaches in acoustic neuroma surgery: case reports.

Hearing conservation surgery for small acoustic neuromas is well accepted. At present, two approaches are primarily used: the suboccipital and the middle fossa. The middle fossa approach to the internal auditory canal has the advantage of using bony landmarks to identify and protect the facial nerve. Because of anatomic constraints presented by the superior semicircular canal however, its uses are limited to intracanalicular tumors or tumors protruding only slightly into the cerebellopontine angle. By extending the approach through the superior semicircular canal, a wide access to the cerebellopontine angle can be safely obtained. In this study three procedures, two through the superior semicircular canal and one through the posterior semicircular canal, were utilized for hearing conservation surgery. By immediately sealing off the canal ends, hearing preservation was accomplished in two out of three of these cases. The dictum that labyrinthine opening invariably leads to anacusis should be reconsidered. By utilizing approaches through the semicircular canal, it is possible that morbidity from this surgery may be reduced.     

Surgical exposure of the facial nerve indications and techniques.

Lesions producing facial nerve palsy may occur within the temporal bone anywhere between the internal auditory canal and the stylomastoid foramen. Surgical exposure of this nerve may be necessary for decompression, grafting, rerouting, or removal of such lesions as acoustic tumour, meningioma, facial nerve neuroma, and cholesteatoma. Contemporary surgical exposure of the facial nerve has as its aim adequate exposure of the facial nerve at any point in its course, with preservation of hearing and vestibular function, without further injury to the facial nerve and the necessity for producing a mastoid cavity. When hearing and balance function are present, the transcanal-transtympanic approach to the horizontal segment of the facial nerve offers limited access to the facial nerve in its tympanic course. Wider exposure is obtained by postauricular transmastoid exposure of the tympanic and mastoid portions of the facial nerve. The middle fossa approach to the facial nerve offers access to the internal auditory canal and labyrinthine portions of the nerve, whereas the retrolabyrinthine approach offers access to the facial nerve in the posterior fossa. Total facial nerve exposure with preservation of hearing and balance function is obtained by the combined transmastoid and middle cranial fossa approach. In individuals who have lost all function of hearing and balance, the postauricular translabyrinthine approach offers total exposure of the facial nerve within the temporal bone and posterior fossa. The aim of this discussion was to present in succinct fashion a systematized approach to surgical exposure of the facial nerve within the temporal bone and posterior fossa.     

Transcanal approach to the singular nerve.

OBJECTIVES/HYPOTHESIS: Intractable benign paroxysmal positional vertigo is rare, and surgery is indicated in only a very small number of cases. Transcanal singular neurectomy is considered a difficult and risky procedure possibly leading to hearing loss and vertigo. The objective of this study was to evaluate the feasibility of the singular neurectomy through the external ear canal in an attempt to explain the contradictory results of previous reports of anatomists and of surgeons who abandoned the technique, considering that the singular neurectomy could not be reached via the external auditory canal without damaging the labyrinth. MATERIALS AND METHODS: Anatomical study on 100 halves of human heads in which the canal of the singular nerve (SN) was identified and opened at its extremities, the internal auditory canal and the ampulla of the posterior semicircular canal, via a posterior fossa approach. Next, the canal of the SN was dissected via the external auditory canal, at the floor of the round window (RW) niche. The relation of the SN canal to the ampulla of the posterior semicircular canal was evaluated. RESULTS: In 90 cases, the canal was transected medially to and away from the ampulla of the posterior semicircular canal, and in 8, at its emergence from the posterior ampullary recess. In these 98 cases, the RW membrane and the bony labyrinth were kept intact. In two cases, the canal of the SN could not be reached at the floor of the RW niche. CONCLUSION: Singular neurectomy is feasible via the external auditory canal, without damaging the RW membrane or the labyrinth in 98% of the cases. Because singular neurectomy is indicated in a very small number of cases, it is difficult to master this particular surgical procedure. This may explain why most surgeons abandoned the technique after a few attempts, followed by an unacceptable rate of sensorineural hearing loss.     

Posterior canal dehiscence syndrome caused by an apex cholesteatoma.

OBJECTIVE: To compare audio-vestibular findings caused by a dehiscence of the posterior semicircular canal with those found in the superior canal dehiscence syndrome. STUDY DESIGN: Case report. SETTING: University hospital, tertiary referral center. PATIENT: The 44-year-old woman suffered from a gradual hearing loss with pulse-synchronous tinnitus as well as sound and pressure-induced vertigo. INTERVENTION: Audio-vestibular testing and high-resolution computed tomography. MAIN OUTCOME MEASURE: The superior canal dehiscence syndrome is caused by failure of normal postnatal bone development in the middle cranial fossa leading to absence of bone at the most superior part of the superior semicircular canal. The typical features for this syndrome are sound- and pressure-induced vertigo with torsional eye movements, pulse synchronous tinnitus and apparent conductive hearing loss in spite of normal middle-ear function. We present a patient with very similar symptoms and findings who, instead, had a posterior semicircular canal dehiscence caused by an apex cholesteatoma. CONCLUSION: Patients with semicircular canal dehiscence have common auditory-vestibular features regardless of which of the two vertical semicircular canals is affected. The only obvious difference between the two is the vertical component of the sound and pressure-induced eye movements (which beats in opposite directions).     

A temporal bone study of posterior semicircular canal resection for exposure of the internal auditory canal (PSCC resection)

Partial resection of the labyrinth is becoming accepted as a means of improving access to the internal auditory canal and central skull base neoplasms. In this investigation, an infralabyrinthine approach was performed on 20 temporal bones. The dissection was extended by transection of the endolymphatic duct, then excision of the posterior semicircular canal. The maximal lateral exposure of the internal auditory canal (IAC) was measured after each manoeuvre. Resection of the posterior semicircular canal increased lateral exposure in 7/20 specimens to an average 61% of the length of the IAC. Posterior canal resection improved superior exposure and increased the circumference of exposure in all specimens.     

Middle fossa vestibular nerve section. A histopathological report.

A patient with Meniere's disease underwent a middle fossa superior and inferior vestibular nerve section with excision of Scarpa's ganglia. Studies of this patient's temporal bone, conducted two and one-half years post-operatively, showed normal cochlear and facial nerves. The internal auditory canal showed fibrosis and new periosteal bone formation. There was complete denervation of the vestibular labyrinth except for the posterior semicircular canal crista. Fibrous and osteoid tissue filled the superior and lateral semicircular canals. In this case, these severe degenerative changes, presumably associated with biochemical changes in the vestibular labyrinth, altered the natural course of Meniere's disease. Vertigo was completely relieved, tinnitus improved, and hearing thresholds stabilized during the course of post-operative follow-up.     

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.     

Particulate Matter in the Posterior Semicircular Canal

The pathoetiology of benign paroxysmal positional vertigo (BPPV) is controversial. Particulate matter within the posterior semicircular canal has been identified intraoperatively in patients with BPPV but has also been reported in non-BPPV patients at the time of translabyrinthine surgery (Parnes LS, McClure JA. Free-floating endolymphatic particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988-92; Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Otorhinolaryngol 1973;20:434-43; Kveton JF, Kashgarian M. Particulate matter within the membranous labyrinth: pathologic or normal? Am J Otol 1994;15:173-6). The nature of the particulate matter remains unknown. The purpose of this study was to prospectively examine the posterior semicircular canal of patients with and without a clinical history of BPPV for the presence of particulate matter. Seventy-three patients without BPPV symptoms undergoing labyrinthine surgery (vestibular schwannoma excision or labyrinthectomy) and 26 patients with BPPV undergoing the posterior semicircular canal occlusion procedure were compared. Additionally, 70 archived temporal bones without a history of BPPV were examined microscopically for the presence of particulate matter within the lumen of the membranous labyrinth. No particles were observed intraoperatively in any of the 73 patients without a history of BPPV. Particulate matter was observed in 8 of 26 patients at the time of the posterior semicircular canal occlusion procedure for intractable BPPV. Of the 70 temporal bones examined, 31 did not show significant postmortem changes and also did not demonstrate cupulolithiasis or canalithiasis. Particulate matter from within the membranous posterior semicircular canal was removed from one patient at the time of posterior semicircular canal occlusion for intractable BPPV symptoms and was examined by scanning electron microscopy. The particulate matter appeared morphologically consistent with degenerating otoconia. These data show a statistically significant association between the presence of particles within the posterior semicircular canal in this study and the symptom complex of BPPV.     

Retrolabyrinthine surgery: anatomy and pathology

Retrolabyrinthine surgery is done to expose the cerebellopontine angle directly through the ear. It is indicated when the hearing in the ear to be operated upon is useful. The surgical technique entails four steps: complete mastoidectomy, extended posterior exposure of the sigmoid sinus, exposure of the posterior fossa dura, and exposure of the cerebellopontine angle. Retrolabyrinthine exposure of the cerebellopontine angle is indicated in tic douloureux, atypical facial pain, and hemifacial spasm. Recently, this approach has been used for sectioning the vestibular nerve, exploration of the posterior fossa to obtain a diagnosis, subtotal resection of large cerebellopontine angle tumors, and for the treatment of other cranial nerve problems. The histopathologic findings in the temporal bones of two patients who underwent retrolabyrinthine removal of cerebellopontine angle masses were reviewed. In one, subtotal resection of an acoustic tumor was attempted to preserve hearing in the presence of a bilateral tumor, with no adverse effect on the middle or inner ear. In the second, retrolabyrinthine exploration of the cerebellopontine angle was done for primary cholesteatoma, and operative injury to the nonampullated end of the posterior semicircular canal was noted. Retrolabyrinthine subtotal resection of large acoustic tumors is advocated in bilateral cases and in elderly persons to delay the inevitable loss of hearing by decompression and partial removal of the tumor mass. In primary cholesteatoma of the cerebellopontine exploration may be indicated to obtain a definitive diagnosis before surgical extirpation of the disease is planned.     

Uszkodzenia ścian kostnych ucha środkowego u chorych operowanych z powodu schorzeń ucha w Klinice Otolaryngologii CM UJ w latach 2008–2012

Background

We perform the middle ear operation to remove pathological tissue and in the next step present ossicular chain reconstruction. Otosurgeon has to also identify bone dehiscences, as a potential way to develop otogenic intracranial and intratemporal complications.

Aim

We analyzed the patients with bone defects in the middle and/or posterior cranial fossa who present also defects of the bony wall of the facial nerve canal and lateral semicircular canal.

Material and methods

We observed 537 patients who were operated on middle ear for the first time in the Department of Otolaryngology at the Jagiellonian University of Cracow from 2008 to 2012. We used a special questionnaire that includes diagnostics of the ear's disease, method of the operation and short- and long-term effects.

Results

We discuss 45 patients with the skull base defects in the middle and/or posterior cranial fossa. Dehiscence of the bony wall of the facial nerve canal was present in 7 patients. In 4 cases semicircular canal fistula coexisted.The most common cause of bone dehiscence was granulation tissue, less frequently cholesteatoma.

Conclusions

1.

Apart from skull base defects in the middle and/or posterior cranial fossa, frequency of bony dehiscence of the facial nerve and semicircular canal fistula is the same as in all population operated on ear.

2.

Defects of the bony wall of the facial nerve and semicircular canal fistula are observed more frequently in granulomatous chronic otitis media than in cholesteatoma chronic otitis media.

3.

We observe the same frequency of intracranial complication in population of patients with defects of the bony wall of the facial nerve canal and horizontal semicircular canal than in all groups with skull base defects.

     

Streptomycin perfusion of the labyrinth in the treatment of Menière’s disease: a modified technique

The ideal surgical procedure for Menière’s disease would combine the high rate of vertigo control and the good hearing preservation of vestibular nerve section with the low morbidity of labyrinthectomy. Shea’s technique of streptomycin perfusion of the labyrinth has been modified by making an additional opening into the posterior semicircular canal in an effort to limit the amount of streptomycin going into the cochlea. Seventeen patients with definite Menière’s with poor hearing have had this procedure. Vertigo was controlled in 94% and the hearing preserved in 55%. Vestibular rehabilitation was not a problem. It is speculated that hearing preservation would be better if the procedure were not restricted to those with poor hearing. This method of destruction of the vestibular system carries the possibility of hearing preservation and maintains the possibility of cochlear implantation should this ever be required.     

Streptomycin perfusion of the labyrinth in the treatment of Menière's disease: a modified technique

The ideal surgical procedure for Menière's disease would combine the high rate of vertigo control and the good hearing preservation of vestibular nerve section with the low morbidity of labyrinthectomy. Shea's technique of streptomycin perfusion of the labyrinth has been modified by making an additional opening into the posterior semicircular canal in an effort to limit the amount of streptomycin going into the cochlea. Seventeen patients with definite Menière's with poor hearing have had this procedure. Vertigo was controlled in 94% and the hearing preserved in 55%. Vestibular rehabilitation was not a problem. It is speculated that hearing preservation would be better if the procedure were not restricted to those with poor hearing. This method of destruction of the vestibular system carries the possibility of hearing preservation and maintains the possibility of cochlear implantation should this ever be required.     

Anatomical studies of the posterior petrous apex with regard to hearing preservation in acoustic neuroma removal

Some surgeons have shown that tumors of the internal auditory canal and cerebello-pontine angle may be removed with preservation of hearing through the suboccipital approach. If hearing is to be conserved, the cochlear division of the VIIIth cranial nerve and blood supply of the labyrinth must be preserved. In addition, surgical entry into the labyrinth, upon removal of the posterior wall of the internal auditory canal, must be avoided since it is likely to result in permanent sensorineural hearing loss. Careful anatomic dissection of 20 human temporal bones has shown that exposure of the lateral-most recess of the internal auditory canal from a suboccipital approach is impossible without injury to the endolymphatic duct, common crus, vestibule or ampulla of the posterior semicircular canal. Previous authors have suggested that exposure of the horizontal crest may be used as a safe landmark in avoiding labyrinthine injury. However, our study has shown that exposure of the horizontal crest usually leads to labyrinthine injury. In 19 out of 20 cases, the labyrinth would have been entered had the horizontal crest been used as a landmark for the lateral limit of bone removal. The application of the anatomical relationships quantified in this study may improve our ability to avoid labyrinthine injury in the suboccipital removal of acoustic neuromas.     

颞下经岩骨前部手术入路的解剖学研究

目的：研究颞下经岩骨前部入路(Kawase入路)的解剖特点。方法:10例20例成人尸头标本在手术显微镜下进行显微解剖和测量。结果：岩骨前部切除后可暴露位于前外例的颈内动脉管水平段，以及颈内动脉管和内听道之间的耳蜗基底转。岩骨前部切除可分别在岩尖上面和内侧面开出面积为2．6cm^2和1．9cm^2的骨窗。与颞下经小脑幕入路相比，暴露范围在斜坡面向下扩大至斜坡上部、在脑干面扩大至椎基底动脉连接部和桥延沟水平。此入路暴露的岩斜坡区硬脑膜主要由脑膜垂体干和咽升动脉供血。结论：Kawase入路可同时暴露中后颅窝，其对后颅窝的暴露范围局限于岩斜坡区上半部。     

Important factors for the hearing loss caused by the triple semicircular canal occlusion in guinea pigs.

HYPOTHESIS: Dynamic recording of the auditory brainstem response is helpful in verifying harmful procedure(s) to hearing during triple semicircular canal occlusion (TSCO) surgery. The damage to the membranous semicircular labyrinth is the single major contributor to hearing loss caused by TSCO. BACKGROUND: Posterior semicircular canal occlusion has been recognized as an efficient method of eliminating vertigo without causing a significant hearing impairment. Recently, TSCO has also been explored for its potential to treat vertigo of various causes. In limited animal studies, varied hearing impairments have been documented after TSCO. However, the major factor(s) causing hearing loss in TSCO is/are unclear. METHODS: Triple semicircular canal occlusion was performed on 36 guinea pigs in total. The cochlear function of the guinea pigs was monitored by observing the auditory brainstem response. The impact of membranous labyrinth damage on hearing was verified by a between-group comparison. RESULTS: Hearing loss during TSCO was accumulated in every step of semicircular canal manipulation. Generally, perilymph leak was found to cause a slight hearing loss that was predominately recovered during surgery. However, transaction of the membranous labyrinth usually caused a more significant hearing loss that was not recovered during the surgery. In addition, the magnitude of hearing loss seemed to be increased with the elongation of the surgery. However, the hearing can be largely recovered after the surgery even in animals with transaction of the membranous labyrinth. CONCLUSION: Hearing loss caused by TSCO can be greatly reduced by avoiding damage to the membranous labyrinth and by shortening the operation time.     

Auditory function in patients with surgically treated superior semicircular canal dehiscence.

OBJECTIVE: To characterize preoperative and postoperative audiologic findings in patients with superior semicircular canal dehiscence syndrome. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Patients with documented superior semicircular canal dehiscence syndrome (according to history, vestibular testing, and high-resolution computed tomography imaging) who underwent surgical repair of their dehiscence. INTERVENTION: Middle fossa craniotomy for superior semicircular canal plugging and/or resurfacing. MAIN OUTCOME MEASURES: Audiologic testing both before and after surgery with pure-tone threshold measurements of air and bone conduction. RESULTS: Twenty-nine subjects underwent surgical repair of superior semicircular canal dehiscence. Overall, there were no statistically significant differences by paired t test in hearing before or after surgery, in either air-conduction or bone-conduction thresholds, for 19 patients that had no previous surgical history. At least partial closure of air-bone gap was achieved in five patients. One patient with previous stapes surgery had significantly worse hearing both before and after canal repair compared with those without previous surgery. Two patients who had undergone previous middle fossa surgery with incomplete resolution of symptoms developed sensorineural hearing loss after revision surgery. Previous middle-ear exploration and tympanostomy tube placement did not seem to affect audiologic outcomes. Surgical hearing results did not differ according to method of canal repair (plugging versus resurfacing). CONCLUSION: Primary middle fossa repair of superior semicircular canal dehiscence is not associated with sensorineural hearing loss and, in some cases, can lead to normalization of conductive hearing loss. Revision middle fossa repair or previous stapes surgery may be associated with postoperative sensorineural hearing loss.     

Extended middle fossa approach to the petroclival junction and anterior cerebellopontine angle.

OBJECTIVES: This article seeks to demonstrate the use of the extended middle cranial fossa approach in the treatment of tumors arising in the anterior cerebellopontine angle and petroclival region. STUDY DESIGN: We conducted a retrospective chart review. SETTING: Tertiary referral center. PATIENTS:: Ten-year retrospective chart review of over 800 skull base surgical cases demonstrated 16 cases in which the senior author used the extended middle cranial fossa as the sole approach to access the posterior cranial fossa, petroclival junction, or the anterior cerebellopontine angle. There were five males and 11 females, 13 meningiomas, 2 trigeminal schwannomas, and 1 brainstem glioma. Presenting symptoms were dependent on extent of brainstem compression and involvement of surrounding cranial nerves. The symptoms are broken down as follows: hydrocephalus, one; balance disturbance, three; diplopia, five; trigeminal neuralgia, two; hemifacial numbness, one; seizures, one; expressive aphasia, one; and hearing loss, two. RESULTS: Of the 16 patients in this study, one patient needed postoperative care in a skilled nursing facility. Postoperative facial nerve weakness was not experienced in any patient. One patient developed a transient cerebrospinal fluid leak that resolved spontaneously. One patient developed a pseudomeningocele secondary to postoperative hydrocephalus. This was corrected with wound exploration and placement of a ventricular peritoneal shunt. Hearing was not maintained in one patient. Two patients developed new fourth nerve paresis and two patients developed new sixth nerve palsies. There were no postoperative infections and no deaths. CONCLUSIONS: The extended middle cranial fossa approach provides excellent access and exposure to tumors in the anterior cerebellopontine angle and petroclival junction. The approach allows more direct access to the area anterior to the internal auditory canal. The key to the approach is adequate bone removal of the petrous apex to provide exposure down to the inferior petrosal sinus and anteriorly to Meckel's cave and the petroclival junction. Extradural elevation of the temporal lobe with suitable brain relaxation minimizes postoperative complications.