Extended Anterior Petrosectomy Through the Transcranial Middle Fossa Approach and Extended Endoscopic Transsphenoidal-Transclival Approach: Qualitative and Quantitative Anatomic Analysis

Mandibular Fossa Approach to Petroclival and Anterior Pontine Lesions

Objective  To describe the anatomy related to a novel approach to the petroclival region through the mandibular fossa for the treatment of petroclival and anterior pontine lesions. Design  Five dry skulls were examined for surgical approach. Three adult cadaveric heads underwent bilateral dissection. One cadaveric head was evaluated with computed tomography after dissection. Setting  This study was performed in an academic medical center. Participants  Neurosurgical anatomy researchers performed this study using dry skulls and cadaveric heads. Main Outcome Measurements  This was a proof-of-concept anatomical study. Results  The mandibular fossa approach uses a vertical preauricular incision above the facial nerve branches. Removal of the temporomandibular joint exposes the mandibular fossa. The anterior boundary is the mandibular nerve at the foramen ovale, and the posterior boundary is the jugular foramen. The chorda tympani, eustachian tube, and tensor tympani muscle are sectioned. The carotid artery is transposed out of the petrous canal, and a petrosectomy is performed from Meckel's cave to the foramen magnum and anterior occipital condyle. Dural opening exposes the anterior pons, vertebrobasilar junction, bilateral vertebral arteries, and the ipsilateral anterior and posterior inferior cerebellar arteries. At completion, the temporomandibular joint is reconstructed with a prosthetic joint utilizing a second incision along the mandible. Conclusions  The mandibular fossa approach is a new trajectory to the petroclival region and the anterior pons. It combines the more anterior angle of endoscopic approaches along with the enhanced control of open approaches. Further study is necessary before this approach is used clinically.

Comparison of the Retrosigmoid Suprameatal and Anterior Subtemporal Transpetrosal Approaches After Full Exposure of the Internal Acoustic Meatus

BACKGROUND AND OBJECTIVES

Surgical approaches to the ventral brainstem and petroclival regions are complex, and standard retrosigmoid and subtemporal approaches are often inadequate. Retrosigmoid suprameatal tubercle (RSMTA) and anterior subtemporal transpetrosal (ASTA) approaches may provide extended surgical exposure with less brain retraction. The objective of this study was to evaluate advantages and disadvantages of RSMTA vs ASTA, and illustrate the surgical corridors and 3-dimensional microsurgical anatomy of the related structures.

METHODS

Four silicone-injected adult cadaver heads (8 sides) were dissected to evaluate the accessibility of lesions located at the petrous apex, ventral brainstem, and pontomedullary region using ASTA and RSTMA.

RESULTS

Both ASTA and RSMTA provide access from the petrous apex to the ventral lower pons and pontomedullary junction. A greater extent of safely resected bone was found in ASTA vs RSMTA. ASTA provides a larger surgical view to the ventrolateral midpons, peritrigeminal region, superior neurovascular complex, pontomesencephalic junction, and posterior cavernous sinus. Meanwhile, through cranial nerve V mobilization, RSMTA provides a larger surgical view to the lower half part of the pons, ventrolateral part of the pontomedullary junction, and middle and lower neurovascular structures.

CONCLUSION

The choice of surgical approach is determined by considering the area where the lesion originates, lesion size, the anatomic structures to which it extends, and evaluation of the area that can be surgically exposed. Our study highlights the differences between these approaches and important surgical anatomic considerations.

Cerebrospinal fluid leakage prevention using the anterior transpetrosal approach with versus without postoperative spinal drainage: an institutional cohort study

The efficacy of spinal drain (SD) placement for cerebrospinal fluid (CSF) leakage prevention after the anterior transpetrosal approach (ATPA) remains unclear. Thus, we aimed to assess whether postoperative SD placement improved postoperative CSF leakage after a skull base reconstruction procedure using a small abdominal fat and pericranial flap and clarify whether bed rest with postoperative SD placement increased the length of hospital stay. This retrospective cohort study included 48 patients who underwent primary surgery using ATPA between August 2011 and February 2022. All cases underwent SD placement preoperatively. First, we evaluated the necessity of SD placement for CSF leakage prevention by comparing the postoperative routine continuous SD placement period to a period in which the SD was removed immediately after surgery. Second, the effects of different SD placement durations were evaluated to understand the adverse effects of SD placement requiring bed rest. No patient with or without postoperative continuous SD placement developed CSF leakage. The median postoperative time to first ambulation was 3 days shorter (P < 0.05), and the length of hospital stay was 7 days shorter (P < 0.05) for patients who underwent SD removal immediately after surgery (2 and 12 days, respectively) than for those who underwent SD removal on postoperative day 1 (5 and 19 days, respectively). This skull base reconstruction technique was effective in preventing CSF leakage in patients undergoing ATPA, and postoperative SD placement was not necessary. Removing the SD immediately after surgery can lead to earlier postoperative ambulation and shorter hospital stay by reducing medical complications and improving functional capacity.

Exposure region of the Kawase approach and its correlation with skull base anatomy: An evaluation with digital models

The Kawase approach is one of the most used trajectories in skull base surgery. The exposure range of the approach and its correlation with skull base anatomy still demand more exploration. With the help of digital rebuilding, analysis, and measurement, we evaluated the exposure range of the Kawase and extended Kawase approaches and analyzed the correlation between the exposure range and the variants of the petrosal and clival anatomy. The finding of the study demonstrated that compared to the sub-temporal approach, the Kawase approach and the extended Kawase approach significantly added the exposure range in the upper, middle, and partial inferior regions of the clivus. The gains in the exposure volume and area are more when the manipulation angle is less than 135°.

Direct Comparison Between the Kawase Approach and Retrosigmoid Intradural Suprameatal Corridor to Access the Petroclival Region Using Computed Tomography Quantitative Volumetric Analysis: A Cadaveric Study

OBJECTIVE

The anterior petrosectomy, also known as the Kawase approach, and the retrosigmoid intradural suprameatal approach (RISA) have both been used to reduce the petrous apex and access the petroclival region. Our goal was to compare the volumes and 3-dimensional shapes of bony resection obtained through each approach while trying to resemble realistic surgical settings.

METHODS

Five cadaveric specimens totaling 10 sides were dissected and analyzed. In every specimen, 1 side was used for the Kawase approach while the opposite side was used for the RISA. Petrosectomy volumes were assessed by comparing preoperative and postoperative thin-sliced computed tomography scans.

RESULTS

Petrosectomy volumes were significantly larger through the Kawase approach than through the RISA (0.82 ± 0.11 vs. 0.49 ± 0.07 cm³, P < 0.001). In addition, surgical maneuverability and freedom were greater in the Kawase operative variant. Lastly, the morphology of the bony window achieved through each approach was clearly different: trapezoid for the anterior petrosectomy versus elongated ellipsoid for the RISA.

CONCLUSIONS

The Kawase approach invariably results in larger volumes of bony removal than the RISA operative variant, and the volume of petrosectomy that is spatially congruent is only partially identical. The Kawase corridor is best suited for middle fossa lesions that extend into the posterior fossa, while the RISA is suitable for pathologies mainly residing in the posterior fossa and extending into the Meckel cave.

Comparison of Anatomic Exposure After Petrosectomy Using Anterior Transpetrosal and Endoscopic Endonasal Approaches: Experimental Cadaveric Study

OBJECTIVE

Transcranial anterior petrosectomy (AP) is a classic approach; however, it is associated with adverse consequences. The endoscopic endonasal approach (EEA) has been developed as an alternative. We describe surgical techniques for AP and EEA and compare the anatomic exposures of each.

METHODS

Ten cadaveric heads (20 sides) were dissected. Specimens were divided into 4 groups: 1) AP, 2) EEA for medial petrosectomy (MP), 3) EEA for inferior petrosectomy (IP), and 4) EEA for inferomedial petrosectomy (IMP). Outcomes were areas of exposure, angles of attack to neurovascular structures, and bone resection volumes.

RESULTS

AP had a greater area of exposure than did MP and IP (P = 0.30, P < 0.01) and had a higher angle of attack to the distal part of the facial nerve-vestibulocochlear nerve (cranial nerve [CN] VII/VIII) complex than did IP and IMP (P < 0.01). MP had a lower angle of attack than IMP to the midpons (P = 0.04) and to the anterior inferior cerebellar artery (P < 0.01). Compared with IMP, IP had a lower angle of attack to the proximal part of the CN VII/VIII complex (P < 0.01) and the flocculus (P < 0.01). The bone resection volume in AP was significantly less than that in MP, IP, and IMP (P < 0.01).

CONCLUSIONS

AP and all EEA techniques had specific advantages for each specific area. We suggest AP for the ventrolateral pons and the anterior superior internal auditory canal, MP for the midline clivus, IP for the ventrolateral brainstem, and IMP to enhance the lateral corridor of the abducens nerve.

Comparative Analysis of Surgical Exposure among Endoscopic Endonasal Approaches to Petrosectomy: An Experimental Study in Cadavers

Objectives  Endoscopic endonasal approaches (EEAs) for petrosectomies are evolving to reduce perioperative brain injuries and complications. Surgical terminology, techniques, landmarks, advantages, and limitations of these approaches remain ill defined. We quantitatively analyzed the anatomical relationships and differences between EEA exposures for medial, inferior, and inferomedial petrosectomies. Design  This study presents anatomical dissection and quantitative analysis. Setting  Cadaveric heads were used for dissection. EEAs were performed using the medial petrosectomy (MP), the inferior petrosectomy (IP), and the inferomedial petrosectomy (IMP) techniques. Participants  Six cadaver heads (12 sides, total) were dissected; each technique was performed on four sides. Main Outcomes and Measures  Outcomes included the area of exposure, visible distances, angles of attack, and bone resection volume. Results  The IMP technique provided a greater area of exposure ( p  < 0.01) and bone resection volume ( p  < 0.01) when compared with the MP and IP techniques. The IMP technique had a longer working length of the abducens nerve (cranial nerve [CN] VI) than the MP technique ( p  < 0.01). The IMP technique demonstrated higher angles of attack to specific neurovascular structures when compared with the MP (midpons [ p  = 0.04], anterior inferior cerebellar artery [ p  < 0.01], proximal part of the cisternal CN VI segment [ p  = 0.02]) and IP (flocculus [ p  = 0.02] and the proximal [ p  = 0.02] and distal parts [ p  = 0.02] of the CN VII/VIII complex) techniques. Conclusion  Each of these approaches offers varying degrees of access to the petroclival region, and the surgical approach should be appropriately tailored to the pathology. Overall, the IMP technique provides greater EEA surgical exposure to vital neurovascular structures than the MP and the IP techniques.

Endoscopic endonasal and transorbital approaches to petrous apex lesions

OBJECTIVE

The petrous apex (PA) is one of the most challenging areas in skull base surgery because it is surrounded by numerous critical neurovascular structures. The authors analyzed the clinical outcomes of patients who underwent endoscopic endonasal approach (EEA) and transorbital approach (TOA) procedures for lesions involving PA to determine the perspectives and proper applications of these two approaches.

METHODS

The authors included patients younger than 80 years with lesions involving PA who were treated between May 2015 and December 2019 and had regular follow-up MR images available for analysis. Patients with meningioma involving petroclival regions were excluded. The authors classified PA into three regions: superior to the petrous segment of the internal carotid artery (p-ICA) (zone 1); posterior to p-ICA (zone 2); and inferior to p-ICA (zone 3). Demographic data, preoperative clinical and radiological findings, surgical outcomes, and morbidities were reviewed.

RESULTS

A total of 19 patients with lesions involving PA were included. Ten patients had malignant tumor (chondrosarcoma, chordoma, and osteosarcoma), and 6 had benign tumor (schwannoma, Cushing's disease, teratoma, etc.). Three patients had PA cephalocele (PAC). Thirteen patients underwent EEA, and 5 underwent TOA. Simultaneous combined EEA and TOA was performed on 1 patient. Thirteen of 16 patients (81.3%) had gross- or near-total resection. Tumors within PA were completely resected from 13 of 16 patients using a view limited to only the PA. Complete obliteration of PAC was achieved in all patients. Postoperative complications included 2 cases of CSF leak, 1 case of injury to ICA, 1 fatality due to sudden herniation of the brainstem, and 1 case of postoperative diplopia.

CONCLUSIONS

EEA is a versatile surgical approach for lesions involving all three zones of PA. Clival tumor spreading to PA in a medial-to-lateral direction is a good indication for EEA. TOA provided a direct surgical corridor to the superior portion of PA (zone 1). Patients with disease with cystic nature are good candidates for TOA. TOA may be a reasonable alternative surgical treatment for select pathologies involving PA.

Endoscopic endonasal and transorbital routes to the petrous apex: anatomic comparative study of two pathways

BACKGROUND AND OBJECTIVE

Surgical approaches to the petrous apex region are extremely challenging; while subtemporal approaches and variations represent the milestone of the surgical modules to reach such deep anatomical target, in a constant effort to develop minimally invasive neurosurgical routes, the endoscopic endonasal approach (EEA) has been tested to get a viable corridor to the petroclival junction. Lately, another ventral endoscopic minimally invasive route, i.e., the superior eyelid endoscopic transorbital approach, has been proposed to access the most lateral aspect of the skull base, including the petrous apex region. Our anatomic study aims to compare and combine such two endoscopic minimally invasive pathways to get full access to the petrous apex. Three-dimensional reconstructions and quantitative and morphometric data have been provided.

MATERIAL AND METHODS

Five human cadaveric heads (10 sides) were dissected. The lab rehearsals were run as follows: (i) preliminary pre-operative CT scans of each specimen, (ii) pre-dissection planning of the petrous apex removal and its quantification, (iii) petrous apex removal via endoscopic endonasal route, (iv) post-operative CT scans, (v) petrous apex removal via endoscopic transorbital route, and (v) final post-operative CT scan with quantitative analysis. Neuronavigation was used to guide all dissections.

RESULTS

The two endoscopic minimally invasive pathways allowed a different visualization and perspective of the petrous apex, and its surrounding neurovascular structures. After both corridors were completed, a communication between the surgical pathways was highlighted, in a so-called connection area, surrounded by the following important neurovascular structures: anteriorly, the internal carotid artery and the Gasserian ganglion; laterally, the internal acoustic canal; superiorly, the abducens nerve, the trigeminal root, and the tentorium cerebelli; inferomedially, the remaining clivus and the inferior petrosal sinus; and posteriorly, the exposed area of the brainstem. Used in a combined fashion, such multiportal approach provided a total of 97% of petrous apex removal. In particular, the transorbital route achieved a mean of 48.3% removal in the most superolateral portion of the petrous apex, whereas the endonasal approach provided a mean of 48.7% bone removal in the most inferomedial part. The difference between the two approaches was found to be not statistically significant (p = 0.67).

CONCLUSION

The multiportal combined endoscopic endonasal and transorbital approach to the petrous apex provides an overall bone removal volume of 97% off the petrous apex. In this paper, we highlighted that it was possible to uncover a common path between these two surgical pathways (endonasal and transorbital) in a so-called connection area. Potential indications of this multiportal approach may be lesions placed in or invading the petrous apex and petroclival regions that can be inadequately reached via transcranial paths or via an endonasal endoscopic route alone.