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Nowadays, the middle cranial fossa approach (MFA) is one of the most useful operative procedures in skull base surgery. When performed properly, it provides a relevant adjunct to treating complex skull base lesions. MFA allows one to resect the anterior petrous bone (anterior petrosectomy), open the internal auditory canal (IAC), and access the lateral wall of the cavernous sinus and the infratemporal fossa. Knowledge of the anatomical structures of the middle cranial fossa and cavernous sinus is mandatory to perform this approach. We report in detail the standard extradural subtemporal route for the anterior petrosectomy and MFA. The main indications for this approach are intradural lesions localized medially to the trigeminal nerve, subtemporal interdural and extradural tumours and neoplasms involving the IAC (including IAC pathology). Moreover, we describe the extended middle fossa approach, consisting in the anterior extension of MFA, indicated for intradural tumours of the superior cerebello-pontine angle and of prepontine clivus (retroclival lesions, ventral brainstem tumours, and cavernomas), for infratemporal fossa lesions, and cavernous sinus pathologies. Even if the anatomical landmarks of the middle cranial fossa and lateral skull base are well known, training with cadaver dissection is necessary for any skull-base surgeon to perform an optimum MFA. The cadaver-lab dissections simplify the learning of anatomical structures, and prepare the surgeon properly for this technically challenging approach.

Background: Trigeminal neuralgia (TN) due to compression from the dolichoectatic vertebrobasilar artery (DVBA) is extremely rare and difficult to treat due to its morphological characteristics. We report two cases of good transposition of DVBA and postoperative course obtained using the anterior petrosal approach and a new vasoculopexy method. Methods: We describe two cases of microvascular decompression (MVD) for refractory TN associated with DVBA. In both cases, MVD was performed through the anterior petrosal approach. The DVBA was decompressed using a GORE-TEX sling and WECK clip in an inferomedial direction. Results: Complete pain relief without new neurological deterioration was achieved immediately in both patients. Conclusion: We experienced a rare condition of TN due to exclusion by the DVBA. The anterior transpetrosal approach was extremely effective in this case. This approach secured the surgical field, allowed transposition of the DVBA, and caused no perioperative complications. [ABSTRACT FROM AUTHOR]

In 1985, Kawase published an anterior petrosal approach to expose the posterior cranial fossa and to minimize retraction of the temporal lobe. However, some neurosurgeons still have difficulty with removing tumors through an anterior petrosal approach because a complete understanding of the Kawase pyramid has not been achieved. We hypothesized that if anterior petrosectomy were performed with three-dimensional understanding of the Kawase pyramid, it would have a positive effect on extent of tumor resection. We performed a retrospective study of patients who underwent surgical treatment for meningioma through an anterior petrosal approach. Patients were divided into total resection and subtotal resection groups, and statistical differences between the groups were analyzed. To identify factors predictive of complete tumor removal, univariable and multivariable logistic regression analyses were performed. Width and height of the drilled internal auditory canal of the total resection group were significantly larger than those of the subtotal resection group (P = 0.001, P = 0.033). The operative angle of the total resection group was significantly larger than that of the subtotal resection group (P < 0.001). Regression analyses showed only drilled internal auditory canal width to be predictive of complete tumor removal, increasing the likelihood of complete tumor removal by 2.778-fold with an increase in drilled internal auditory canal width by 1 mm (P = 0.023). Insufficient petrosectomy during an anterior petrosal approach adversely affects the extent of tumor resection. Furthering three-dimensional understanding of the Kawase pyramid could aid in complete tumor resection and better outcomes without causing damage to the surrounding organs. [ABSTRACT FROM AUTHOR]

The anterior petrosal approach, or Kawase's approach, is a commonly used technique in skull base surgery to access the brainstem in the posterior fossa from the middle fossa, and has the advantages of minimizing brain retraction and preserving hearing. It was first successfully performed by the legendary Japanese neurosurgeon, Takeshi Kawase, for the clipping of a basilar artery aneurysm in 1981. To date, no historical article has shed light on Kawase's intriguing personal history. In this historical vignette, the authors depict Kawase's unique background, talent, passion, as well as struggles that ultimately shaped his career. By sharing Kawase's personal story from the hospital where he first successfully performed his original approach, the authors hope to pass on to future generations Kawase's spirit and philosophy that have impacted the global neurosurgical community.

The mainstay treatment for petrous apicitis (Gradenigo's syndrome) is medical management with antibiotics, steroids, and placement of pressure equalization tubes. The role for surgery is limited as second-line treatment if conservative methods have failed. We report 2 cases of medically refractory petrous apicitis presenting with progressive cranial neuropathies who underwent petrous apex resection and debridement via an anterior petrosal (Kawase) approach. Both patients had improvement of their preoperative cranial nerve deficits within 24–48 hours of surgery, that previously did not improve after 2 weeks of medical management. To our knowledge, the use of the Kawase approach for petrous apicitis has not been previously reported. In addition, we postulate that surgical intervention can potentially result in quicker recovery of preexisting cranial nerve deficits in medically refractory petrous apicitis. This raises the potential role of earlier surgical intervention. [ABSTRACT FROM AUTHOR]

Brainstem cavernoma is a challenging neurosurgical pathology and microsurgery remains the only treatment option. Although the decision-making between interventional and conservative approach to this disease may be complex, malformations presenting multiple bleedings are usually good candidates for surgery. 1 On the other hand, microsurgical resection of cavernomas can offer an effective resolution with acceptable morbidity. In this video, we present a case of pontine cavernoma with multiple hemorrhages in a young patient. The anatomical characteristic of the lesion defines the best suitable craniotomy for surgery. In this case, an anterior petrosal approach 234 was used to access the peritrigeminal area and safely perform the resection. Anatomical considerations are described on this skull base approach along with the rationale and benefits of this exposure. Electrophysiological neuromonitoring is essential for this kind of procedure and preoperative tractography also enabled the best understanding of the disease. Finally, we also discuss alternative managements and potential complications. 5 With the patient's consent, we also show the excellent clinical evolution after few weeks of recovery and the restoration of the corticospinal tract, previously displaced by the cavernoma, to its original position. [ABSTRACT FROM AUTHOR]

Background: The combined anterior transpetrosal and subtemporal/transcavernous (atsta) approach to the petroclival junction provides a wide exposure facilitating resection of large tumor lesions such as petroclival mengiomas, chondrosarcomas, or chordomas. In this article we provide technical instructions on the approach with anatomical consideration and a literature review of previous applications of this approach. Methods: The combined approach was performed in two cadaveric specimen and relevant anatomical aspects were studied. Additionally, the authors performed a review of the literature focusing on indications, neurologic outcome, and complications associated with the technique. Results: A combined atsta approach offers a wide exposure of the crus cerebrum, pons, basal temporal lobe, cranial nerves III to VII/VIII, posterior cerebral artery (PCA), superior cerebellar artery (SCA), basilar artery (BA), anterior inferior cerebellar artery (AICA), and posterior communicating artery (Pcom). It has been successfully applied with acceptable morbidity and mortality rates, mainly for (spheno-) petroclival meningiomas. Conclusion: The combined approach studied here is a useful skull base approach to the petroclival junction and can be applied to treat large or complex pathologies of the region. Detailed anatomical knowledge is essential. [ABSTRACT FROM AUTHOR]

Background: Primary solitary plasmacytoma (PSP) of the skull base is a rare localized monoclonal plasma cell dyscrasia with normal or low plasma cell infiltration. Differentiating from other skull base tumors based on radiologic findings is difficult due to nonspecific features. PSP has a better prognosis after surgical resection and adjuvant radiotherapy, unless the tumor progresses to multiple myeloma (MM). Nonetheless, 50-60% progress to MM within a median time of 2 years. Gross total resection (GTR) for PSP is controversial for improving overall survival. However, if the lesion is easily accessible, for example, nonskull base lesion, GTR is still advocated. Case Description: A 67-year-old male patient presented with right occipital neuralgia and diplopia in the last year. Neurological examination revealed mild abducens paresis on the right side. Brain MRI scan showed a large petroclival bony extradural mass lesion on the right side, with homogeneous enhancement, extending from the dorsum sellae to the ipsilateral occipital condyle and involving the petrous carotid artery. Brain CT scan revealed an osteolytic lesion without intratumoral calcifications, sclerotic border, or periosteal reaction. Anterior petrosal approach was performed and GTR was achieved. The patient had good postoperative outcome and improvement of symptoms. Postoperative MRI revealed GTR. Total body imaging work-up and immunohistochemistry confirmed PSP. Conclusion: Although the extent of resection in the outcome is controversial, maximal safe resection of skull base PSP should be considered to improve symptoms and quality of life. [ABSTRACT FROM AUTHOR]

The combined petrosal approach is an essential technique for the skull base neurosurgeon. In this manuscript, the authors provide a brief history of the development of this approach, technical instruction with consideration of important landmarks, and a literature review of the broad range of clinical applications for this approach. The combined petrosal approach was performed bilaterally in 6 cadaveric injected specimens. The relationship of middle and posterior fossa dura, venous sinuses, cranial nerves (CNs), and the vascular anatomy were studied. Additionally, the authors performed a systematic review of the literature to elucidate the clinical applications, technical considerations, outcomes, and complications associated with the combined petrosal approach. Several critical details of the approach are outlined. The approach offers a magnified view of this region and inflicts minimal damage to the temporal bridging veins while entering the transverse sinus no more than 5 mm anterior to Citelli’s angle. The approach allows for visualization of CN IV as an important anatomical landmark, while preserving the venous integrity of posterior cavernous sinus. The literature review surveys 11 studies that provide a range of clinical applications for the approach. The authors conclude that the combined petrosal approach is one of the most versatile skull base approaches to the middle and posterior fossa, and it can be used to address complex pathologies of the petroclival region. Detailed knowledge of its technical nuances and applications is essential for any skull base surgeon. [ABSTRACT FROM AUTHOR]

Surgical approaches to the pons lump together different areas of the pons, such as the anterosuperior and the anteroinferior pons. These areas are topographically different, and different approaches may be best suited for one or the other area. We evaluated the exposure of the anterosuperior pons using different surgical approaches. We quantify the surgical exposure and surgical freedom to the anterosuperior pons afforded by the pterional transtentorial (PT), the orbitozygomatic with anterior clinoidectomy (OZ), and the anterior petrosal (AP) approaches. Five embalmed cadaver heads were used. The three approaches were executed on each side, for a total of 30 approaches. The area of maximal exposure of the anterosuperior pons was measured with the aid of neuronavigation. We also evaluated the feasible angles of approach in the vertical and horizontal planes. We were able to successfully expose the anterosuperior pons using all the selected approaches. In the PT and OZ approaches, mobilization of the sphenoparietal sinus can prevent over-retraction of the temporal bridging veins, while use of the endoscope can help in preserving the integrity of the fourth nerve while cutting the tentorium. The mean exposure area was largest for the AP and smallest for the PT; the surgical freedom was similar among all the approaches. However, there was no statistically significant difference among all the approaches in the exposure area or in the surgical freedom. There is no significant difference among the three evaluated approaches in exposure of the anterosuperior pons. [ABSTRACT FROM AUTHOR]

Objectives Numerous surgical approaches have been developed to access the petroclival region. The Kawase approach, through the middle fossa, is a well-described option for addressing cranial base lesions of the petroclival region. Our aim was to gather data about the variation of cranial nerve locations in diverse petroclival pathologies and clarify the most common pathologic variations confirmed during the anterior petrosal approach. Method A retrospective analysis wasmade of both videos and operative and histologic records of 40 petroclival tumors from January 2009 to September 2013 in which the Kawase approach was used. The anatomical variations of cranial nerves IV-VI related to the tumor were divided into several location categories: superior lateral (SL), inferior lateral (IL), superior medial (SM), inferior medial (IM), and encased (E). These data were then analyzed taking into consideration pathologic subgroups of meningioma, epidermoid, and schwannoma. Results In 41% of meningiomas, the trigeminal nerve is encased by the tumor. In 38% of themeningiomas, the trigeminal nerve is in the SL part of the tumor, and it is in 20% of the IL portion of the tumor. In 38% of the meningiomas, the trochlear nerve is encased by the tumor. The abducens nerve is not always visible (35%). The pathologic nerve pattern differs from that of meningiomas for epidermoid and trigeminal schwannomas. Conclusion The pattern of cranial nerves IV-VI is linked to the type of petroclival tumor. In a meningioma, tumor origin (cavernous, upper clival, tentorial, and petrous apex) is the most important predictor of the location of cranial nerves IV-VI. Classification of four subtypes of petroclival meningiomas using magnetic resonance imaging is very useful to predict the location of deviated cranial nerves IV-VI intraoperatively. [ABSTRACT FROM AUTHOR]

Background: Trigeminal neuralgia (TN) due to compression from the dolichoectatic vertebrobasilar artery (DVBA) is extremely rare and difficult to treat due to its morphological characteristics. We report two cases of good transposition of DVBA and postoperative course obtained using the anterior petrosal approach and a new vasoculopexy method., Methods: We describe two cases of microvascular decompression (MVD) for refractory TN associated with DVBA. In both cases, MVD was performed through the anterior petrosal approach. The DVBA was decompressed using a GORE-TEX sling and WECK clip in an inferomedial direction., Results: Complete pain relief without new neurological deterioration was achieved immediately in both patients., Conclusion: We experienced a rare condition of TN due to exclusion by the DVBA. The anterior transpetrosal approach was extremely effective in this case. This approach secured the surgical field, allowed transposition of the DVBA, and caused no perioperative complications., Competing Interests: There are no conflicts of interest., (Copyright: © 2022 Surgical Neurology International.)

Brainstem cavernoma is a challenging neurosurgical pathology and microsurgery remains the only treatment option. Although the decision-making between interventional and conservative approach to this disease may be complex, malformations presenting multiple bleedings are usually good candidates for surgery. 1 On the other hand, microsurgical resection of cavernomas can offer an effective resolution with acceptable morbidity. In this video, we present a case of pontine cavernoma with multiple hemorrhages in a young patient. The anatomical characteristic of the lesion defines the best suitable craniotomy for surgery. In this case, an anterior petrosal approach 2 3 4 was used to access the peritrigeminal area and safely perform the resection. Anatomical considerations are described on this skull base approach along with the rationale and benefits of this exposure. Electrophysiological neuromonitoring is essential for this kind of procedure and preoperative tractography also enabled the best understanding of the disease. Finally, we also discuss alternative managements and potential complications. 5 With the patient's consent, we also show the excellent clinical evolution after few weeks of recovery and the restoration of the corticospinal tract, previously displaced by the cavernoma, to its original position., Competing Interests: Conflict of Interest None declared., (Thieme. All rights reserved.)

Objective  The anterior petrosal approach is an extension of the middle fossa approach, characterized by drilling of the posteromedial triangle of the middle fossa. Drilling the Kawase's rhomboid creates a surgical corridor to the posterior fossa after splitting the tentorium. We present a case of a petrous apex meningioma invading the tentorium and causing trigeminal neuralgia. Results  The patient was positioned in a Mayfield with the head rotated. A frontotemporal incision was done. A basal craniotomy was done to allow epidural dissection. The anatomical landmarks were identified. The surgical video is analyzed together with cadaveric dissections to highlight landmarks when doing an anterior petrosectomy. The tentorium was identified and the infiltrated region was coagulated and removed. The tentorium was sharply sectioned until the free edge of the tentorium was opened. The tumor in the petrous apex was identified and removed. The trigeminal nerve was decompressed and a gross total resection was achieved with resolution of the symptoms. Conclusion  The anterior petrosal approach is a useful corridor to remove tumors in the petrous apex that infiltrate the tentorium. A thorough knowledge of the anatomical landmarks is crucial to identify and delineate the limits of the Kawase's rhomboid. After evaluating different surgical corridors, the anterior petrosal approach allows a gross total resection including the removal of the infiltrated tentorium and a resolution of the symptoms. The link to the video can be found at: https://youtu.be/p4KPUnM_bww. [ABSTRACT FROM AUTHOR]

Objective  The anterior petrosal approach is an extension of the middle fossa approach, characterized by drilling of the posteromedial triangle of the middle fossa. Drilling the Kawase's rhomboid creates a surgical corridor to the posterior fossa after splitting the tentorium. We present a case of a petrous apex meningioma invading the tentorium and causing trigeminal neuralgia. Results  The patient was positioned in a Mayfield with the head rotated. A frontotemporal incision was done. A basal craniotomy was done to allow epidural dissection. The anatomical landmarks were identified. The surgical video is analyzed together with cadaveric dissections to highlight landmarks when doing an anterior petrosectomy. The tentorium was identified and the infiltrated region was coagulated and removed. The tentorium was sharply sectioned until the free edge of the tentorium was opened. The tumor in the petrous apex was identified and removed. The trigeminal nerve was decompressed and a gross total resection was achieved with resolution of the symptoms. Conclusion  The anterior petrosal approach is a useful corridor to remove tumors in the petrous apex that infiltrate the tentorium. A thorough knowledge of the anatomical landmarks is crucial to identify and delineate the limits of the Kawase's rhomboid. After evaluating different surgical corridors, the anterior petrosal approach allows a gross total resection including the removal of the infiltrated tentorium and a resolution of the symptoms. The link to the video can be found at: https://youtu.be/p4KPUnM&#95;bww .

OBJECTIVE Reports about endoscopic endonasal surgery for skull base tumors involving the lateral part of petrous apex remain scarce. The authors present their experience with the endoscopic transsphenoidal anterior petrosal (ETAP) approach through the retrocarotid space for tumors involving the internal auditory canal, jugular fossa, and cavernous sinus. METHODS The authors performed the ETAP approach in 10 patients with 11 tumors (bilateral in 1 patient) that extensively occupied the lateral part of petrous apex, e.g., the internal auditory canal and jugular fossa. Eight patients presented with diplopia (unilateral abducens nerve palsy), 3 with tinnitus, and 1 with unilateral hearing loss with facial palsy. After wide anterior sphenoidotomy, the sellar floor, clival recess, and carotid prominence were verified. Tumors were approached via an anteromedial petrosectomy through the retrocarotid triangular space, defined by the cavernous and vertical segments of the internal carotid artery (ICA), the clivus, and the petrooccipital fissure. The surgical window was easily enlarged by drilling the petrous bone along the petrooccipital fissure. After exposure of the tumor and ICA, dissection and resection of the tumor were mainly performed under direct visualization with 30° and 70° endoscopes. RESULTS Gross-total resection was achieved in 8 patients (9 tumors). In a patient with invasive meningioma, the tumor was strongly adherent to the ICA, necessitating partial resection. Postoperatively, all 8 patients who had presented with abducens nerve palsy preoperatively showed improvement within 6 months. In the patient presenting with hearing loss and facial palsy, the facial palsy completely resolved within 3 months, but hearing loss remained. Regarding complications, 3 patients showed mild and transient abducens nerve palsy resolving within 2 weeks, 3 months, and 6 months. Postoperative CSF rhinorrhea requiring surgical repair was observed in 1 patient. No patient exhibited hearing deterioration, facial palsy, or symptoms of lower cranial nerve palsy after surgery. CONCLUSIONS The ETAP approach can offer a simple, less invasive option for invasive skull base tumors involving petrous regions, including the internal auditory canal, jugular fossa, and cavernous sinus. The ETAP approach can reach more extensive areas in the extradural regions around the petrous bone. The authors' results indicate that the transsphenoidal retrocarotid route is sufficient to approach the petrosal areas in select cases. Further expansion of the surgical field is not always necessary. However, experience with intradural lesions remains limited, and the extent of tumor resection largely depends on tumor characteristics. Application of the ETAP approach should thus be carefully determined in each patient, taking into consideration the size of the retrocarotid window and tumor characteristics.

Object: 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., Methods: 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., Results: 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)., Conclusions: Anterior petrosectomy can be performed more efficiently by using the cochlear line as a key landmark to preserve the cochlea.

Flow reduction therapy is sometimes utilized for difficult aneurysms, but it does not always work. A 42-year-old man presented with headache, dizziness, and slight gait disturbance due to left thrombosed giant vertebral aneurysm. Clip ligation of the VA after the PICA origin was performed for flow reduction based on the CFD analysis. Two months later, the aneurysm showed minor hemorrhage and hydrocephalus, and thrombectomy and clip reconstruction of the VA was performed. He returned to work with slight ipsilateral facial palsy (House & Brackmann grade 2). The video can be found here: http://youtu.be/-AUVk6nxefQ.