A Comparison between the Kawase and Extended Retrosigmoid Approaches (Retrosigmoid Transtentorial and Retrosigmoid Intradural Suprameatal Approaches) for Accessing the Petroclival Tumors. A Cadaveric Study

Background The aim of our study was to compare the area of exposure at the ventral brainstem and petroclival region offered by the Kawase, retrosigmoid transtentorial (RTT), and the retrosigmoid intradural suprameatal (RISA) approaches in cadaveric models. Methods We performed 15 approaches (five each of the Kawase, RISA, and RTT approaches) on silicone-injected adult cadaver heads. Ventral brainstem and petroclival areas of exposure were measured and compared. Results The mean ventral brainstem area exposed by the Kawase approach was 55.00 ± 24.1 mm², significantly less than that exposed by RTT (441 ± 63.3 mm²) and RISA (311 ± 61 mm²) (p < 0.05). The area of ventral brainstem exposure was significantly more via RTT than through RISA (p = 0.01). The mean petroclival area of exposure through the Kawase approach was significantly smaller than that obtained through the RTT and RISA approaches (101.7 ± 545.01 mm², 696 ± 57.7 mm², and 716.7 ± 51.4 mm², respectively). Conclusion Retrosigmoid approaches provide a greater exposure of the brainstem and petroclival areas. The Kawase approach is ideally suited for lesions around the Meckel cave with an extension into the middle fossa. These approaches can be used in conjunction with one another to access petroclival tumors.     

Quantitative Comparison of Retrosigmoid Intradural Suprameatal Approach and Retrosigmoid Transtentorial Approach: Implications for Tumors in the Petroclival Region

Background Retrosigmoid transtentorial (RTT) and retrosigmoid intradural suprameatal (RISA) approaches have been used in the treatment of petroclival tumors.Objective To compare the area of exposure of brainstem and petroclival region obtained through RTT and RISA in cadaveric specimens.Methods Five cadaveric specimens with a total of 10 sides were analyzed. RTT and RISA were performed on five sides each. Brainstem and petroclival surface exposure were measured using both the approaches. These values were compared between the two approaches.Results Brainstem area exposure with RTT was 441 ± 63 mm² and that with RISA was 311 ± 61 mm². Student''s t-test revealed that the difference was significant (p = 0.01). The area of petroclival exposure medial to the Meckel cave through RTT was 696 ± 57 mm², and that through RISA was 716 ± 51 mm² (p = 0.69). The area of brainstem exposure between V and VII-VII complex through RTT and RISA was 387 ± 86 mm² and 378 ± 76 mm² (p = 0.87).Conclusion The RTT approach is an excellent approach to ventrolateral brainstem and petroclival region. It provides greater superoventral exposure of the ventrolateral brainstem than RISA and provides similar petroclival exposure.     

Opening cranial cisterns by the anterior subtemporal keyhole approach to the superior petroclival region: anatomical study and comparative analysis

Background

Without drilling the bony structures, simple incision of the tentorium dorsal to the porus of trochlear nerve by the anterior subtemporal keyhole approach provides narrow exposure in the superior petroclival region. This study was designed to measure and compare the areas of exposure, linear distances, and angles of approach in the superior petroclival region before and after opening cranial cisterns.

Methods

The study was carried out on 20 sides of cadaver heads. With the use of a navigation system, the area of exposure in the dorsum sella and clivus, the ventrolateral area of exposure in brainstem around the BA, the linear exposure of the posterior petroclinoid fold and BA trunk, and the angles of approach to BA tip were evaluated. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus between trochlear porus, the linear exposure of the trigeminal nerve, and the angle to the most inferior medial point in clivus were also measured.

Results

The area of exposure in the dorsum sella and clivus (157.6 ± 27.2mm²), the ventrolateral area of exposure in brainstem around BA (249.5 ± 29.7mm²), the linear exposure of the posterior petroclinoid fold (11.5 ± 0.6 mm) and BA trunk (10.3 ± 2.0 mm), and the angle of approach in the vertical axis to the BA tip (13.7° ± 1.7°) were significantly greater after opening cisterns. The angles of approach in the horizontal axis to the BA tip (24.5° ± 1.1° vs 24.7° ± 0.8°) were not statistically different. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus and trochlear porus, the linear exposure of the trigeminal nerve, and the angle of approach to the most inferior medial point in clivus were 6.7 ± 1.3 mm, 10.7 ± 2.4 mm, 9.6 ± 2.3 mm, 15.8 ± 1.4 mm, and 13.0° ± 1.5°, respectively.

Conclusion

The areas of exposure, linear distances, and the angles of approach in the superior petroclival region can be increased after opening cranial cisterns by the anterior subtemporal keyhole approach.     

An endoscopic-assisted technique for retrosellar access during the extended retrosigmoid approach: a cadaveric feasibility study and quantitative analysis of retrosellar working area

The retrosigmoid approach has been advocated for certain petroclival tumors but provides limited access to any retrosellar extension of tumor, necessitating a two-stage operation. Our purpose was to demonstrate preliminary feasibility of an endoscopic-assisted technique to provide retrosellar access during the extended retrosigmoid approach and compare microscopic and endoscopic retrosellar working area. Standard retrosigmoid craniectomy and partial petrosectomy respecting inner ear structures were performed on six embalmed cadaveric heads. Two balloons were inflated to simulate a 15 mm petroclival tumor. Retrosellar clival and brainstem working area and ipsilateral oculomotor nerve and posterior cerebral artery (PCA) working distance were measured using the endoscope and microscope. Artificial tumors were implanted and resected using the endoscopic-assisted technique to assess feasibility. The endoscope provided significantly greater mean working area/distance on the clivus (201.6 vs 114.8 mm², p?<?0.01), brainstem (223.5 vs 121.2 mm², p?<?0.01), ipsilateral oculomotor nerve (10.8 vs 6.4 mm, p?<?0.01), and ipsilateral PCA (13.7 vs 8.9 mm, p?=?0.01). Petrous dissection to create a 10?×?10 mm working channel and artificial tumor resection was feasible in all dissections. The superior petrosal vein required ligation in 9 (75 %) cases. Air cells were exposed in 1 (8 %) case. The described endoscopic-assisted technique can provide retrosellar access during the extended retrosigmoid approach to access petroclival tumors with retrosellar extension. Risks include superior petrosal vein sacrifice, bleeding that can impair visualization, injury to the trigeminal nerve during endoscopic insertion/manipulation or injury to the brainstem while working in the medial limits of exposure. Further work is necessary to determine clinical feasibility, safety, and efficacy.     

Volumetry and Analysis of Anatomical Variants of the Anterior Portion of the Petrous Apex Outlined by the Kawase Triangle Using Computed Tomography

Background Anterior petrosectomy has become an increasingly used approach for petroclival lesions. This study measures the volume and the anatomical variants of the anterior portion of the petrous apex outlined by the Kawase triangle using computed tomography (CT). Methods This was a transversal retrospective study. We assessed the anterior petrous apex portion outlined by the Kawase triangle in consecutive patients > 18 years of age from CT scans of temporal bone stored in an archive system. The volumetry was performed on a workstation. Results A total of 154 petrosal apex were analyzed in 77 patients (36 men). The average volume of the region outlined by the Kawase triangle was 1.89 ± 0.52 cm³. The volume average in men was 2.01 ± 0.58 cm³, and the average in women was 1.79 ± 0.41 cm³. Intra- and interobserver agreement were both excellent, and there was little variance. Nineteen petrous apex demonstrated anatomical variations. In 18 cases it was pneumatized, and in one case a vascular or nerve-like structure was identified, a report we did not find in the literature. Conclusion The volumetry of the petrous apex anterior portion outlined by the Kawase triangle can be made by CT with excellent intra- and interobserver agreement and reproducibility. There are anatomical variants in this region that are relevant to surgery.     

Extended endoscopic endonasal transclival approach to the ventrolateral brainstem and related cisternal spaces: anatomical study

Advances in endoscopic endonasal skull base surgery have led to the development of new routes to areas beyond the midline skull base. Recently, feasible surgical corridors to the lateral skull base have been described. The aim of this study was to describe the anatomical exposure of the ventrolateral brainstem and posterior fossa through an extended endoscopic endonasal transclival transpetrosal and transcondylar approach. Six human heads were used for the dissection process. The arterial and venous systems were injected with red- and blue-colored latex, respectively. A pre- and postoperative computed tomography (CT) scan was carried out on every head. The endoscopic endonasal transclival approach was extended through an anterior petrosectomy and a medial condylectomy. A three-dimensional model of the approach was reconstructed, using a dedicated software, from the overlapping of the pre- and post-dissection CT imaging of the specimen. An extended endoscopic transclival approach allows to gain access through an extradural anterior petrosectomy and medial condylectomy to the anterolateral surface of the brainstem and the posterior fossa. Two main intradural anatomical corridors can be described: first, between the V cranial nerve in the prepontine cistern and the VII–VIII cranial nerves in the cerebellopontine and cerebellomedullary cistern; second, between the VII–VIII cranial nerves and the IX cranial nerve, in the premedullary cistern. Extending the transclival endoscopic approach by performing an extradural anterior petrosectomy and a medial condylectomy provides a safe and wide exposure of the anterolateral brainstem with feasible surgical corridors around the main neurovascular structures.     

Quantitative analysis of the working area and angle of attack for the retrosigmoid, combined petrosal, and transcochlear approaches to the petroclival region

OBJECT: The authors quantitatively assessed the working areas and angles of attack associated with retrosigmoid (RS), combined petrosal (CP), and transcochlear (TC) craniotomies. METHODS: Four silicone-injected cadaveric heads were bilaterally dissected using three approaches progressing from the least to the most extensive. Working areas were determined using the Optotrak 3020 system on the upper and middle thirds of the petroclivus and brainstem. Angles of attack were studied using the Elekta SurgiScope at the Dorello canal and the origin of the anterior inferior cerebellar artery (AICA). The TC approach provided significantly greater (p < 0.001) working areas at the petroclivus (755.6 +/- 130.1 mm2) and brainstem (399.3 +/- 68.2 mm2) than the CP (354.1 +/- 60.3 and 289.7 +/- 69.9 mm2) and RS approaches (292.4 +/- 59.9, 177.2 +/- 54.2 mm2, respectively). The brainstem working area associated with the CP approach was significantly larger (p < 0.001) than that associated with the RS route. There was no difference in the petroclival working area comparing the CP and RS approaches (p = 0.149). The horizontal and vertical angles of attack achieved using the TC approach were wider than those of the CP and RS at the Dorello canal and the origin of the AICA (p < 0.001). CONCLUSIONS: The CP approach offers a more extensive working area than the RS for lesions involving the anterolateral surface of the brainstem, but not for petroclival lesions. The TC approach provides the widest corridor, improving the working area and angle of attack to both areas, but hearing must be sacrificed and the facial nerve is at risk.     

Intradural anterior transpetrosal approach

The standard anterior transpetrosal approach (ATPA) for petroclival lesions is fundamentally an epidural approach and has been practiced for many decades quite successfully. However, this approach has some disadvantages, such as epidural venous bleeding around foramen ovale. We describe here our experience with a modified technique for anterior petrosectomy via an intradural approach that overcomes these disadvantages. Five patients with petroclival lesions underwent surgery via the intradural ATPA. The intraoperative hallmarks are detailed, and surgical results are reported. Total removal of the lesions was achieved in two patients with petroclival meningioma and two patients with pontine cavernoma, whereas subtotal removal was achieved in one patient with petroclival meningioma without significant morbidity. No patient experienced cerebrospinal fluid leakage. The intradural approach is allowed to tailor the extent of anterior petrosectomy to the individually required exposure, and the surgical procedure appeared to be more straightforward than via the epidural route. Caveats encountered with the approach were the temporal basal veins that could be spared as well as identification of the petrous apex due to the lack of familial epidural landmarks. The risk of injury to the temporal bridging veins is higher in this approach than in the epidural approach. Intradural approach is recommended in patients with a large epidural venous route, such as sphenobasal and sphenopetrosal vein. Navigation via bone-window computed tomography is useful to identify the petrous apex.     

Postauricular, transpetrous, presigmoid approach for extensive skull base tumors in the petroclival region: the successes and the travails

Purpose  

Postauricular, transpetrous, presigmoid approach combines a supra/infratentorial exposure with partial petrosectomy to access third to the twelfth cranial nerves and extraaxial lesions situated anterolateral to brainstem. It provides a shorter working distance to large petrosal, petroclival, cerebellopontine, and cerebellomedullary cisternal lesions and their extensions to the subtemporal–infratemporal areas. This study reviews the surgical technique, corridors of extension, and complications encountered utilizing this approach for excising extensive lesions in these locations.     

Combined extradural subtemporal and anterior transpetrosal approach to tumors located in the interpeduncular fossa and the upper clivus

Background

Central skull base lesions in the interpeduncular fossa and the upper clival regions can be challenging to access because of their location anterior to the brainstem. We have modified the anterior transpetrosal approach by combination with the extradural subtemporal route to increase the surgical corridor.

Methods

Thirty-seven patients underwent surgical treatment via the anterior transpetrosal approach from 2002 to 2012. The combined surgical approach was primarily applied when the tumors arose from the upper clival portion and extended to the interpeduncular fossa. The combined approach was used in seven of these patients, comprising four patients with petroclival meningiomas, one patient with sphenoclival meningiomas, one patient with trigeminal schwannoma, and one patient with an epidermoid cyst extending from the interpeduncular fossa to the prepontine cistern.

Results

The combined approach permitted excellent visualization of the interpeduncular fossa in addition to the upper clivus and the lateral aspect of the brain stem. Mobilization of the temporal lobe by the entire epidural dissection of the lateral wall of the cavernous sinus facilitates access via the subtemporal route. The transient symptom of the temporal lobe in the dominant site may be the only drawback for this combined approach, although it may disappear immediately after the surgery.

Conclusion

The present approach combines Dolenc’s approach and Kawase’s approach, providing a wide exposure to lesions of the interpeduncular fossa and the clivus.     

Usefulness of facial nerve monitoring for confirmation of greater superficial petrosal nerve in anterior transpetrosal approach

Introduction

The greater superficial petrosal nerve (GSPN) is especially important in anterior transpetrosal approach (ATPA) as the most reliable superficial landmark of Kawase’s triangle. The GSPN can be considered as the superficial lateral border of anterior petrosectomy on the middle fossa to avoid internal carotid artery (ICA) injury. Although experienced operators can find the GSPN, its confirmation is not always easy to achieve.

Methods

We introduce our recent GSPN confirmation methods using facial nerve monitoring. In 10 recent cases, antidromic GSPN stimulation and free-running facial muscle electromyography (EMG) monitoring were performed.

Results

Facial nerve evoked-EMG by antidromic GSPN stimulation confirmed the location of the GSPN course with precision in all cases. Free-running facial muscle EMG informed the mechanical stress of facial nerves through the GSPN. There was no postoperative facial palsy or dry eye in these cases.

Conclusions

GSPN confirmation and preservation are not always easy to achieve. These monitoring methods are useful for the confirmation of the GSPN, which is a landmark for safe extradural anterior petrosectomy, and for the preservation of the GSPN itself.     

Long term surgical results of 154 petroclival meningiomas: A retrospective multicenter study

BackgroundOutcomes of petroclival meningiomas (PCM) (morbidity, permanent cranial nerves deficit, tumor removal and recurrence) are inconsistent in the literature, making it a challenge to predict surgical morbidity.MethodsA multicenter study of patients with PCMs larger than 2.5 cm between 1984 and 2017 was conducted. The authors retrospectively reviewed the patients’ medical records, imaging studies and pathology reports to analyze presentation, surgical approach, neurological outcomes, complications, recurrence rates and predictive factors.ResultsThere were 154 patients. The follow-up was 76.8 months on average (range 8–380 months). Gross total resection (GTR) was achieved in 40 (26.0%) patients, subtotal resection (STR) in 101 (65.6%), and partial resection in 13 (8.3%). Six (2.6%) perioperative deaths occurred. The 5-year, 10-year and 15-year progression-free survival (PFS) of GTR and STR with radiation therapy (RT) was similar (100%, 90% and 75%). PFS of STR without adjuvant radiation was associated with progression in 71%, 51% and 31%, respectively. Anterior petrosectomy and combined petrosectomy were associated with higher postoperative CN V and CN VI deficits compared to the retrosigmoid approach. The latter had a significantly higher risk of CN VII, CN VIII and LCN deficit. Temporal lobe dysfunction (seizure and aphasia) were significantly associated with the anterior petrosectomy approach.ConclusionsOur study shows that optimal subtotal resection of PCMs associated with postoperative RT or stereotactic radiosurgery results in long-term tumor control to equivalent radical surgery. Case selection and appropriate intraoperative judgement are required to reduce the morbidity.     

Detailed anatomy knowledge: first step to approach petroclival meningiomas through the petrous apex. Anatomy lab experience and surgical series

Petroclival meningiomas are a challenge for neurosurgeons due to the complex anatomy of the region that is rich of vessels and nerves. A perfect and detailed knowledge of the anatomy is very demanding in neurosurgery, especially in skull base surgery. The authors describe the microsurgical anatomy to perform an anterior petrosectomy based on their anatomical and surgical experience and perform a literature review. The temporal bone is the most complex and fascinating bone of skull base. The apex is located in the angle between the greater wing of the sphenoid and the occipital bone. Removing the petrous apex exposes the clivus. The approach directed through the temporal bone in this anatomical area is referred to as an anterior petrosectomy. The area that must be drilled is the rhomboid fossa that is defined by the Kawase, premeatal, and postmeatal triangles. In Division of Neurosurgery - University of Turin, 130 patients, from August 2013 to September 2015, underwent surgical resection of intracranial meningiomas. In this group, we have operated 7 PCMs and 5 of these were approached performing an anterior petrosectomy with good results. In our conclusions, we feel that this surgery require an advanced knowledge of human anatomy and a specialized training in interpretation of radiological and microsurgical anatomy both in the dissection lab and in the operating room.     

Combined petrosal approach to petroclival meningiomas

OBJECTIVE: To study the use and advantages of combining the posterior petrosal approach with the anterior petrosal approach to petroclival meningiomas. METHODS: Seven cases of petroclival meningiomas operated on via the combined petrosal approach were retrospectively analyzed. The basis on which this approach was selected was assessed, as were its benefits and risks. RESULTS: Gross total resection was achieved in five of the seven patients. No mortality or decrease in Karnofsky performance score was observed at the time of the last follow-up examination. Six of the seven patients had serviceable hearing before the operation. Only one patient lost hearing after the operation, and this hearing loss occurred in only one ear. Before the operation, six patients were House-Brackmann facial nerve function Grade I, and one patient was Grade II to III. At the last follow-up examination, facial nerve function was Grade I in five patients, Grade II in one patient, and Grade V in one patient. Tumors in all patients involved the cavernous sinus, Meckel's cave, petroclival junction, and middle clivus. All patients possessed a large posterior fossa component of tumor measuring an average of 3.6 x 3.5 x 4.2 cm. In four patients, the tumor was attached for the entire width of the clivus to the contralateral petroclival junction. Four patients displayed central brainstem compression. Four patients displayed bony changes at the petrous apex. All patients displayed total or partial encasement of the vertebrobasilar artery and its major branches. CONCLUSION: The combined petrosal approach should be considered for patients who have a large petroclival meningioma and serviceable hearing. This approach enhances petroclival exposure and the degree of tumor resection, especially in the area of the petroclival junction, middle clivus, apical petrous bone, posterior cavernous sinus, and Meckel's cave. The combined petrosal approach also allows better visualization of the contralateral side and the ventral brainstem, which facilitates safe dissection of the tumor from the brainstem, the basilar artery, and the perforators. If a patient has an early draining bridging vein to the tentorial sinus (before it reaches the transverse-sigmoid junction) or a prominent sigmoid sinus and jugular bulb, the combined petrosal approach provides significant working space.     

A limited anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for ventral brainstem tumor removal

BACKGROUND: The present study describes the use of a limited subtemporal extradural anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for the management of tumors located behind the clivus and ventral to the brainstem. Details of the procedure and its application in five cases are presented. METHODS: This procedure consists of using the extradural route to approach the upper side of the petrosal pyramid so that it can be drilled medially, and to resect the apex to come out into the posterior fossa. This route gives a petrosectomy just medial to the horizontal segment of the petrous carotid artery in front of the cochlea. It goes around the labyrinthine mass and the internal auditory canal from above to expose the posterior fossa dura between the two petrosal sinuses. The dural opening exposes the ventral aspect of the pons from the trigeminal nerve to the origin of the abducens nerve, ventral to the facial nerve. Preoperative embolization of the inferior petrosal sinus allows its intraoperative section for a wider exposure along the lower clivus. This approach can easily be combined with an intradural approach to provide additional exposure above the trigeminal nerve. Patients who underwent this procedure had prepontine cisternal chordoma or epidermoid cyst of the petroclival region. RESULTS: One patient experienced a cranial nerve deficit as a direct result of the surgical procedure (VIth nerve palsy requiring surgery) but no other patient has had permanent neuromuscular compromise. Complications consisted of a wound infection in one case. Tumor removal was total in three cases and partial in two cases. CONCLUSION: Quite easy to master, the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.     

Temporopolar epidural transcavernous transpetrous approach. Technique and indications

BACKGROUND AND PURPOSE: Several selective approaches have been recommended for access to the petroclival region (PCR). However, locoregional extension of the tumor may necessitate more extensive procedures. Dissections from injected specimens allowed us to describe the different osteodural triangles that are exposed to provide an extensive access to the PCR. METHOD: The bony step included a temporopterional flap and exposure of the paraclinoid carotid after removal of the anterior clinoid process. The sphenoid wing was then extensively drilled, exposing the foramen rotundum and ovale. An anterior petrosectomy was subsequently performed. The dura propria of the cavernous sinus was elevated as far as the Meckel cave. The sylvian fissure was also opened. Then, the temporobasal dura and the dura from the posterior surface of the petrous bone were opened and the superior petrosal sinus was coagulated and divided. The tentorium was divided toward its free edge. RESULTS: Via this approach, cranial nerves from the olfactory tract to the acousticofacial bundle are exposed. In the same way, the ventral and lateral surface of the pons is identified. CONCLUSION: The epidural temporopolar transcavernous transpetrous approach is useful to expose during the same procedure, elements of the posterior and middle cranial fossa. It is of particular value when managing tumors simultaneously involving the PCR, the parasellar, and the suprasellar regions.     

Mandibular asymmetry: a three-dimensional quantification of bilateral condyles

Introduction

The shape and volume of the condyle is considered to play an important role in the pathogenesis of the mandibular deviation. Curvature analysis is informative for objectively assess whether the shape of the condyles matches that of the glenoid fossa. In this study, a three-dimensional (3-D) quantification of bilateral asymmetrical condyles was firstly conducted to identify the specific role of 3-D condylar configuration for mandibular asymmetry.

Methods

55 adult patients, 26 males (26?±?5 yrs) and 29 females (26?±?5 yrs), diagnosed with mandibular asymmetry were included. The examination of deviation of chin point, deviation of dental midlines, inclination of occlusal plane, and depth of the mandibular occlusal plane were conducted. After the clinical investigation, computed tomography images from the patients were used to reconstruct the 3-D mandibular models. Then the condylar volume, surface size, surface curvature and bone mineral density were evaluated independently for each patient on non-deviated and deviated sides of temporomandibular joint.

Results

Both the condylar surface size and volume were significantly larger on deviated side (surface size: 1666.14?±?318.3 mm², volume: 1981.5?±?418.3 mm³). The anterior slope of the condyle was flatter (0.12?±?0.06) and the posterior slope (0.39?±?0.08) was prominently convex on the deviated side. The corresponding bone mineral density values were 523.01 ±118.1 HU and 549.07 ±120. 6 HU on anterior and posterior slopes.

Conclusions

The incongruence presented on the deviated side resulted in a reduction in contact areas and, thus, an increase in contact stresses and changes of bone density. All aforementioned results suggest that the difference existing between deviated and non-deviated condyles correlates with facial asymmetrical development. In mandibular asymmetry patients, the 3-D morphology of condyle on deviated side differ from the non-deviated side, which indicates the association between asymmetrical jaw function and joint remodeling.

     

Brain stem cavernoma excised by subtemporal-infratemporal approach

Brain stem cavernomas are most safely removed through the pial surface at which the cavernoma is surfacing. When a lower pontine or an upper medullary cavernoma comes to the surface of the anterior portion of the brain stem, it is difficult to reach by traditional approaches. We describe a case of mid- and lower pontine cavernoma, surfacing anteriorly, which was completely excised by the subtemporal-infratemporal approach. After making a small temporal craniotomy and a zygomatic osteotomy, the petrous carotid artery was mobilized anteriorly and the petroclival bone was drilled away to reach the anterior surface of the pons using the subtemporal-infratemporal approach. A small incision was made on the anterior surface of the pons, between the CN V and CN VI and the cavernoma was completely excised with the aid of the surgical microscope and the neuro-endoscope. Immediately after the operation, the patient had a complete abducens palsy and a mild increase of left hemiparesis, both of which resolved completely within 3 months. The patient returned to the full time work without any neurological deficit. A follow-up MRI 1 year later showed the complete excision of the cavernoma. The subtemporal-infratemporal approach is useful for anteriorly located mid to lower pontine and upper medullary cavernomas.     

幕上下经岩骨乙状窦前入路切除巨大岩斜部肿瘤

目的 探讨幕上下经岩骨乙状窦前入路切除岩斜部肿瘤手术的技巧及并发症。方法 取颞枕游离骨瓣,分别于迷路前后将乳突及岩骨根部大部切除,但保留骨性半规管、耳蜗及鼓室的完整性;结扎并切断岩上窦,自乙状窦前方抵达岩斜部。结果 ４１例肿瘤包括脑膜瘤２０例,表皮样囊肿２０例,神经鞘瘤１例。手术全切肿瘤３４例,近全切除６例,大部切除１例。术后一过性失语１０例,脑水肿６例。脑干梗塞２例,第Ⅲ、Ⅵ、Ⅶ及后组颅神经损伤     

Functional and oncological outcome of petroclival chondrosarcoma operated on through an extradural anterior petrosectomy approach. A single center experience

BackgroundManagement of skull base chondrosarcoma (SBC) remains challenging due to its deep location and complex growth pattern. Non-total resection and postoperative residual mass are common features, with controversy regarding the need to offer systematic postoperative radiation therapy or additional surgery.MethodsA single-center retrospective cohort study was conducted on 10 consecutive patients harboring petroclival chondrosarcomas that were operated on between May 2007 and March 2019. After resection, the patients were allocated to a wait-and-rescan policy.ResultsPatients were operated on through an extradural anterior petrosectomy (EAP). Subtotal tumor resection was achieved in all patients. The mean duration of follow-up was 70 months (range 25–137/median 67 months). Clinical outcomes dramatically improved in three (30%) patients, while five patients retained preoperative cranial nerve (CN) disturbances after surgery (50%). Two patients reported transient postoperative worsening of their symptoms (20%). All of the postoperative CN new deficits improved within one year, except in one patient who showed permanent facial nerve palsy. The preoperative median Karnofsky Performance Scale (KPS) score was 80 (range 70–100), and then it became 90 (range 70–100) postoperatively. Patients harboring a tumor residue were included in a wait-and-rescan policy. With this regimen, tumor control was obtained in seven patients (70% of cases until the last follow-up). Three patients (30%) showed progression of the residual; two of them were treated with adjuvant therapy, while an extra cranial growth residue was observed in the third.ConclusionOptimal and reasonable surgical resection of petroclival chondrosarcomas could be achieved with good to excellent functional outcomes through an EAP. In spite of a significant percentage of regrowth, only one patient required additional salvage surgery.