Anterior Petrosectomy Research Articles

Morphometry relevant to Anterior Petrosectomy with special reference to Kawase’s Triangle

Abstract Background and aims :The petrous apex and the middle cranial fossa is a commonly explored area in neurosurgeries and hence require a holistic approach which should include the possibility of anatomical variants and morphometric dissimilarities. Material and Methods:This morphometric study was undertaken on 91 dry adult skulls [182 petrosal apices] to analyze a number of parameters relevant to Anterior Petrosectomy [AP] via the Kawase’s Triangle [KT]. The anatomical landmarks most pertinent to Anterior Petrosectomy [Kawase's approach] were defined, recorded and validated. The findings of the study were compared with earlier workers who have employed other means of investigation viz. dry bones/CT scans or cadaveric studies . Results : The parameters undertaken for the study presented with variable values and moresoever for the surface area of the KT. This can be very logically attributed to the variant anatomy amongst races and also to the physiological status of the individual Conclusions : AP has evolved as a preferred method for approaching petroclival region and thus requires an in depth understanding. The present analysis throws significant light on certain parameters that would be helpful in making anterior petrosectomy safer. Surgeries of the skull base demand for high end precision and proficiency and thus our findings provide enhanced alertness for a better and safe procedure. A methodical approach to the area with the background knowledge of these parameters shall culminate in desired neurosurgical outcomes.

Extended Middle Fossa Approach With Anterior Petrosectomy and Anterior Clinoidectomy for Resection of Spheno-Cavernous-Tentorial Meningioma: The Hakuba-Kawase-Dolenc Approach: 3-Dimensional Operative Video.

Extended Middle Fossa Approach With Anterior Petrosectomy and Anterior Clinoidectomy for Resection of Spheno-Cavernous-Tentorial Meningioma: The Hakuba-Kawase-Dolenc Approach: 3-Dimensional Operative Video.

Hearing Preservation during Anterior Petrosectomy: The “Cochlear Safety Line”

Background: The localization of cochlea during anterior petrosectomy is important to prevent inadvertent surgical damage and thus, hearing loss. Till date, no optimal method to determine the position of the cochlea relative to the Kawase quadrangle has been devised to ensure the protection of the cochlea while performing the Kawase approach.

Technical nuances of subtemporal approach for the treatment of basilar tip aneurysm.

Background:Basilar tip aneurysms are one of the most complex vascular lesions to treat surgically because of their location, depth of the approach, and close proximity of vital neurovascular structures such as the mesencephalon, cranial nerves, perforating arteries to the thalamus. There are different surgical approaches utilized to reach basilar tip aneurysms, namely, pterional, pretemporal, orbitozygomatic, subtemporal, and anterior petrosectomy. Each of them has its advantages and limitations.Methods:In this paper, we present our personal experience with the use of subtemporal approach. The technique is described in detail including its nuances and potential pitfalls.Results:The subtemporal approach is indicated for basilar tip aneurysms located at the level of the floor of the sella turcica to 1 cm above the dorsum sellae.Conclusion:Subtemporal approach offers good surgical corridor for the management of these complex vascular lesions.

Morphometry relevant to anterior petrosectomy with special reference to Kawase’s triangle

Background and aims : The petrous apex and the middle cranial fossa is a commonly explored area in neurosurgeries and hence require a holistic approach which should include the possibility of anatomical variants and morphometric dissimilarities. Material and Methods: This morphometric study was undertaken on 91 dry adult skulls [182 petrosal apices] to analyze a number of parameters relevant to Anterior Petrosectomy [AP] via the Kawase’s Triangle [KT]. The anatomical landmarks most pertinent to Anterior Petrosectomy [Kawase’s approach] were defined, recorded and validated. The findings of the study were compared with earlier workers who have employed other means of investigation viz. dry bones/CT scans or cadaveric studies. Results: The parameters undertaken for the study presented with variable values and moresoever for the surface area of the KT. This can be very logically attributed to the variant anatomy amongst races and also to the physiological status of the individual Conclusions: AP has evolved as a preferred method for approaching petroclival region and thus requires an in depth understanding. The present analysis throws significant light on certain parameters that would be helpful in making anterior petrosectomy safer. Surgeries of the skull base demand for high end precision and proficiency and thus our findings provide enhanced alertness for a better and safe procedure. A methodical approach to the area with the background knowledge of these parameters shall culminate in desired neurosurgical outcomes.

Hearing Preservation During Anterior Petrosectomy: The “Cochlear Safety Line”

Identification and protection of the cochlea during anterior petrosectomy is key to prevent hearing loss. Currently, there is no optimal method to infer the position of the cochlea in relation to the Kawase quadrangle; therefore, damage to the cochlea during anterior petrosectomy remains a substantial risk. To identify and define landmarks available during anterior petrosectomy to locate the cochlea and prevent its damage. The Kawase approach was simulated in 11 cadaveric specimens. After a subtemporal craniotomy, foramen spinosum and ovale were identified. Anterior petrosectomy was performed, and the upper dural transitional fold (UDTF) was identified. Two virtual lines, from foramen spinosum (line A), and the lateral rim of the foramen ovale (line B), were projected to intersect the UDTF perpendicularly. The cochlea was exposed, and the distances between lines A and B and the closest point of the outer rim and membranous part of the cochlea were measured. The average distance between line A to the bony and membranous edges of the anteromedial cochlea was-0.62 ± 1.38 mm and 0.38 ± 1.63 mm, respectively. The average distance between line B to the bony and membranous edges of the cochlea was 1.82 ± 0.99 mm and 2.78 ± 1.29 mm, respectively. Line B (cochlear safety line) never intersected the cochlea. The cochlear safety line is a reliable landmark to avoid the cochlea during the Kawase approach. When expanding the anterior petrosectomy posteriorly, the cochlear safety line can be used as a reliable landmark to prevent exposure of the cochlea, thus preventing hearing loss.

Anterior Petrosectomy and Resection of a Meckel's Cave Schwannoma

Anterior Petrosectomy and Resection of a Meckel's Cave Schwannoma

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.

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.

How I do it: the combined petrosectomy.

Petroclival and ventral brain stem tumors require a complex approach. The combined petrosectomy is an epidural transtentorial-transpetrosal otoneurosurgical approach to achieve a retrolabyrinthine presigmoidal approach and an anterior petrosectomy in one single procedure. The different steps of this approach are described and illustrated by figures and a video. The indications and limitations of the technique are presented. The combined petrosectomy offers multiple corridors to the petroclival region and ventral brainstem while preserving the intrapetrous neurotological structures. Meticulous stepwise bony resection optimizing the dural opening and preservation of veins contributes to reducing the risk inherent to this technique.

The cochlea in skull base surgery: an anatomy study.

OBJECTIVE The object of this study was to examine the relationships of the cochlea as a guide for avoiding both cochlear damage with loss of hearing in middle fossa approaches and injury to adjacent structures in approaches directed through the cochlea. METHODS Twenty adult cadaveric middle fossae were examined using magnifications of ×3 to ×40. RESULTS The cochlea sits below the floor of the middle fossa in the area between and below the labyrinthine segment of the facial nerve and greater petrosal nerve (GPN) and adjacent to the lateral genu of the petrous carotid. Approximately one-third of the cochlea extends below the medial edge of the labyrinthine segment of the facial nerve, geniculate ganglion, and proximal part of the GPN. The medial part of the basal and middle turns are the parts at greatest risk in drilling the floor of the middle fossa to expose the nerves in middle fossa approaches to the internal acoustic meatus and in anterior petrosectomy approaches. Resection of the cochlea is used selectively in extending approaches through the mastoid toward the lateral edge of the clivus and front of the brainstem. CONCLUSIONS An understanding of the location and relationships of the cochlea will reduce the likelihood of cochlear damage with hearing loss in approaches directed through the middle fossa and reduce the incidence of injury to adjacent structures in approaches directed through the cochlea.

Morphometric Analysis of Bone Resection in Anterior Petrosectomies.

Introduction The anterior petrosectomy is a well-defined skull base approach to lesions such as petroclival meningiomas, posterior circulation aneurysms, petrous apex lesions (chondrosarcomas, cholesteatomas), ventrolateral brainstem lesions, clival chordomas, trigeminal neurinomas, and access to cranial nerves III, IV, V, and VII. Methods and Materials Fourteen anterior petrosectomies on eight cadaveric heads were performed in a skull base dissection laboratory. Predissection and postdissection thin-cut computed tomography scans were obtained to compare the bone resection. A computer program was used (InVivo5, Anatomage, San Jose, California, United States) to measure the bone resection and the improved viewing angle. Results The average bone removed in each plane was as follows: anterior to posterior plane was 10.57 mm ± 2.00 mm, superior to inferior was 9.39 mm ± 1.67 mm, and lateral to medial was 17.46 mm ± 4.64 mm. The average increased angle of view was 13.01 ± 2.35 degrees (Table 1). The average volume was 1786.94 ± 827.40 mm(3). Conclusions Anterior petrosectomy is a useful approach to access the ventrolateral brainstem region. We present a cadaveric study quantitating the volume of bone resection and improvement in the viewing angle. These data provide useful preoperative information on the utility of this skull base approach and the gain in the viewing angle after bony removal.

Anterior petrosal approach: The safety of Kawase triangle as an anatomical landmark for anterior petrosectomy in petroclival meningiomas

ObjectAnterior petrosectomy through the middle fossa is a well-described option for addressing cranial base lesions of the petroclival region.To access posterior fossa through middle fossa, we quantitatively evaluate the safety of Kawase triangle as an anatomical landmark. MethodWe reviewed pre- and postoperative Multi-Slice CT scan (1mm thickness) of patients with petroclival meningioma between Jan 2009 and Sep 2013 in which anterior petrosectomy was performed to access the posterior fossa part of the tumor. The distances between drilling start and finish edge to the vital anatomical skull base structures such as internal auditory canal (IAC) and superior semicircular canal and petrous apex (petrous part of the carotid artery) were measured and analyzed. ResultsDrilling entrance length is directly related with tumor size. The distances between anatomical structures and drilling points decrease with increasing tumor size, but it always remains a safe margin between drilling points and IAC, internal carotid artery (ICA), and semicircular canals in axial and coronal views. ConclusionThe Kawase triangle is shown to be a safe anatomical landmark for anterior petrosectomy. The described landmarks avoid damage to the vital anatomical structures during access to the posterior fossa through middle fossa, despite temporal bone anatomical variations and different tumor sizes.

Which Strategy for Petroclival Tumors?

Access to the petroclival region has always been challenging owing to the surrounding neurovascular structures. The ideal approach to the region depends not only on the specific tumor characteristics, but also on surgeon preference. In this video article, we have highlighted the use of the modified Dolenc-Kawase approach to expand the standard anterior petrosectomy corridor for challenging tumors that need additional exposure.1, 2, 3, 4, 5 A 60-year-old woman presented with facial sensory loss and occasional diplopia. On radiological investigation, a densely calcified petroclival lesion was identified (Video 1). A temporal craniotomy with zygomatic osteotomy was performed followed by deroofing of the superior orbital fissure, saucerization of the foramen spinosum, and coagulation and division of the middle meningeal artery. The temporal dura propria was then dissected off the lateral wall of cavernous sinus using a combination of sharp and blunt dissection to expose the modified Dolenc-Kawase rhomboid. A T-shaped dural incision was made along with tentorial sectioning and division of the superior petrosal sinus. Owing to dense calcification in the tumor, a bone Cavitron ultrasonic aspirator (CUSA; Integra LifeSciences, Princeton, New Jersey, USA) was used for debulking of the tumor. Tumor was removed piecemeal alternately using the bone CUSA and scissors. Tumor was dissected from above and below the trigeminal nerve that forms the center of the corridor followed by dissection off the sixth cranial nerve as it enters the Dorello canal. An endoscope may be used at the end to ensure complete removal of the tumor.

Anterior Petrosectomy: Consecutive Series of 46 Patients with Attention to Approach-Related Complications.

Objective Anterior petrosectomy(AP) was popularized in the 1980s and 1990s as micro-neurosurgery proliferated. Original reports concentrated on the anatomy of the approach and small case series. Recently, with the advent of additional endonasal approaches to the petrous apex, the morbidity of AP remains unclear. This report details approach-related morbidity around and under the temporal lobe. Methods A total of 46 consecutive patients identified from our surgical database were reviewed retrospectively. Results Of the 46 patients, 61% were women. Median age of the patients was 50 years (mean: 48 ± 2 years). Median follow-up of this cohort was 66 months. Most procedures dealt with intradural pathology (n = 40 [87%]). Approach-related morbidity consisted of only two patients (4%) with new postoperative seizures. There were only two significant postoperative hemorrhages (4%). Cerebrospinal fluid leakage occurred in two patients (4%) requiring reoperation. Conclusion Approach-related complications such as seizures and hematoma were infrequent in this series, < 4%. This report describes a contemporary group of patients treated with open AP and should serve as a comparison for approach-related morbidity of endoscopic approaches. Given the pathologies treated with this approach, the morbidity appears acceptable.

Which Routes for Petroclival Tumors? A Comparison Between the Anterior Expanded Endoscopic Endonasal Approach and Lateral or Posterior Routes

Petroclival tumors remain a surgical challenge. Classically, the retrosigmoid approach (RSA) has long been used to reach such tumors, whereas the anterior petrosectomy (AP) has been proposed to avoid crossing cranial nerves. More recently, the endoscopic endonasal approach has been "expanded" (i.e., EEEA) to the petroclival region. We aimed to compare these 3 approaches to help in the surgical management of petroclival tumors. Petroclival approaches were performed on 5 specimens after they were prepared with formaldehyde colored via latex injection. The EEEA provides a simple straightforward route to the clivus, but reaching the petrous apex requires the surgeon to circumvent the internal carotid artery either via a medial transclival, an inferior transpterygoid, or a lateral variant through the Meckel's cave. In contrast, the AP offers a narrow direct superolateral access to the petroclival region crossed by the trigeminal nerve. Finally, the RSA provides a wide simple and quick exposure of the cerebellopontine angle, but access to the petroclival region needs the surgeon to deal with the V(th) to XI(th) cranial nerves. The EEEA should be preferred for extradural midline tumors (chordomas, chondrosarcomas) or for cystic lesions when drainage is essential. The AP could be optimal for the radical removal of intradural vascularized tumors (meningiomas) with intrapetrous or supratentorial extensions. The RSA retains an advantage for small or cystic tumors near the internal acoustic meatus. The skull base surgeon has to master all of these routes to choose the more appropriate one according to the surgical objective, the tumor characteristics, and the patient's medical status.

Cochlear line: a novel landmark for hearing preservation using the anterior petrosal approach.

The goal of this study was to develop a practical landmark for the safe and easy identification of the cochlea when performing anterior petrosectomy based on cadaver dissection results. The cochlear line was defined as the line drawn from the crossing point between the greater superficial petrosal nerve (GSPN) and the petrous internal carotid artery to the line drawn over the apex of the superior circumference of the dura of the internal auditory canal at a right angle. The validity of the cochlear line marking the anteromedial perimeter of the cochlea at the angle of the GSPN and the internal acoustic canal as a practical landmark were evaluated using 5 cadaver heads. The mean distance (± SD) measured from the cochlear line to the margin of the cochlear cavity was 2.25 ± 0.51 mm (range 1.50-3.00 mm). Anterior petrosectomy can be performed more efficiently by using the cochlear line as a key landmark to preserve the cochlea.

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

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. 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. 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. 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.

Anterior Petrosectomy: Consecutive Series of 46 Patients with Attention to Approach-Related Complications

Objective: Surgical approaches to the petrous apex, such as anterior petrosectomy, were popularized in the 1980s. Original reports concentrated on the anatomy of the approach and small case series. Recently, with the advent of additional endonasal approaches to the petrous apex, it remains unclear as to what is the morbidity of anterior petrosectomy? Here, we report a contemporary series of anterior petrosectomy detailing its complications. Methods: Overall 46 consecutive patients identified from our surgical database and were reviewed. Results: Of 46 total patients, 61% were women. Median age of patients was 50. Median follow-up was 66 months. Of the 37 patients with sole anterior petrosectomy, 17 were achieved through a temporal craniotomy, and 20 through a fronto-temporo-orbitozygomatic craniotomy. Most procedures dealt with intradural pathology including meningioma (46%), aneurysms (13%), and schwannoma (13%). Approach-related morbidity consisted of only two (4%) patients with new postoperative seizures. CSF leakage occurred in two patients (4%) requiring reoperation. Facial sensation and diplopia were pathology specific. Conclusion: Complications such as seizures and hematoma were infrequent in this series, less than 7%. This report serves as a contemporary group of patients treated with open anterior petrosectomy and should serve as a comparison for related morbidity of endoscopic approaches, given the morbidity appears acceptable in open anterior petrosectomy group.

The Safety of Kawase Triangle as an Anatomical Landmark for Anterior Petrosectomy in Petroclival Meningiomas

Objective: Anterior petrosectomy through the middle fossa is a well-described option for addressing cranial base lesions of the petroclival region. To access posterior fossa through middle fossa we evaluate quantitatively the safety of Kawase triangle as an anatomical landmark. Methods: We reviewed pre- and postoperative CT scans of patients with petroclival meningioma between January, 2009 and September, 2013 in which anterior petrosectomy were performed to access the posterior fossa part of the tumor. The distances between drilling start edge and drilling finish edge to the vital anatomical skull base structures such as internal carotid artery (IAC) and superior semicircular and petrous apex also drilling entrance length in coronal and axial views were measured and analyzed. Results: Drilling entrance length is directly related with tumor size. The distances between anatomical structures and drilling points decrease with increasing tumor size but always a safe margin remains between drilling points and internal auditory canal, internal carotid artery and semicircular canals in axial and coronal views. Conclusion: Kawase triangle is a safe anatomical landmark for anterior petrosectomy. Staying in such triangle avoid damages to the vital anatomical structures while accessing posterior fossa via middle fossa.