Contralateral transmaxillary corridor: an augmented endoscopic approach to the petrous apex.

Contemporary skull base surgeons must understand transcranial and endoscopic endonasal approaches to the petrous apex (PA). We provide an anatomic overview and comparison of main approaches to the PA through illustrative anatomic dissections. On 10 sides of 5 specimens, transcranial approaches to the PA including the anterior petrosal, transcochlear, and retrosigmoid with suprameatal extension were performed. For endoscopic endonasal approaches, the transclival approach was performed in the midline of 5 specimens and its contralateral transmaxillary extension was performed on 10 sides. The anterior petrosal approach offers an anterolateral view of the PA bounded by petrous ridge posteromedially, internal auditory canal posterolaterally, greater superficial petrosal nerve anterolaterally, and lateral boundary of cranial nerve V, the Gasserian ganglion, and V3 anteromedially; it exposes the middle fossa and, once the PA is removed, the superomedial cerebellopontine angle. The transcochlear approach affords a lateral view of the PA defined medially and inferiorly by inferior petrosal sinus, posteriorly by posterior fossa dura, anteriorly by the petrous internal carotid artery, and superiorly by the superior petrosal sinus and middle fossa dura. Through a retrosigmoid approach, the PA is bounded by the superior petrosal sinus superiorly, the sagittal plane of cranial nerve VI medially, and the axial and sagittal plane of the internal auditory canal porus inferiorly and laterally, respectively. It affords a panoramic view of the posterior fossa and access to Meckel's cave after PA drilling. Endoscopic endonasal approaches target the anteromedial PA, and it is demarcated by a triangle consisting of cranial nerve VI posterolaterally, the paraclival segment of the internal carotid artery anteriorly, and the petroclival synchondrosis inferiorly and medially. The addition of the contralateral transmaxillary approach enhances lateral access up to the internal auditory canal. We provide a comprehensive overview of the main approaches to the PA through illustrative anatomic dissections and representative cases.

The petrous apex is one of the most challenging areas of the skull base to access. We present a case of residual petrous apex chordoma posterolateral to the paraclival segment of the internal carotid artery (ICA) resected with combined endoscopic endonasal and contralateral transmaxillary (CTM) approaches, without lateralization of the ICA. This case demonstrates the value of the CTM corridor in resecting petrous apex lesions that are posterolateral to the paraclival segment of the ICA.

Accessing the petrous apex (PA) via an endoscopic endonasal approach (EEA) is challenging due to its posterior and lateral anatomical relationship with the paraclival carotid artery. Typically, the EEA requires the mobilization or compression of the vessel and the use of angled-lens endoscopes and instruments. A sublabial contralateral transmaxillary (CTM) corridor has been used to overcome these challenges. Still, it requires extensive osteo-meatal disruption and drilling of the medial pterygoid process, which risks the vidian nerve and increases nasal morbidity. Furthermore, the CTM corridor positions the endoscope in the same horizontal plane as the instruments passing through the nostrils, leading to fencing. The authors propose a novel minimally invasive route to the PA, the precaruncular contralateral medial transorbital (cMTO) corridor, to address these issues. This anatomical study compares the EEA+CTM and EEA+cMTO corridors in accessing the PA. The authors dissected 14 fresh, preinjected cadaveric specimens (28 sides) using neuronavigation to complete EEA, cMTO, and CTM on each side. In addition to qualitative analysis, they measured and compared the working distance between the entry point (nose, orbit, maxilla) and the petrosal process of the sphenoid bone (PPSB), superomedial PA, and foramen lacerum (FL); angle of attack (AoA); area of surgical freedom; endoscope-instrument fencing angle; and visual angle for each approach. The cMTO corridor provided the shortest working distance to the petroclival region (PA = 67.4 ± 4.47 mm, PPSB = 67.57 ± 4.33 mm, and FL = 66.30 ± 4.77 mm) compared to the CTM (PA = 75.85 ± 3.63 mm, PPSB = 76 ± 3.96 mm, and FL = 74.52 ± 4.26 mm) and to the EEA (PA = 85.16 ± 3.16 mm, PPSB = 84.55 ± 3.02 mm, and FL = 83.42 ± 3.21 mm, p < 0.001). Both CTM and cMTO corridors had a similar visual angle to the PA (20.72° ± 2.16° and 21.63° ± 1.84°, respectively), offering a similar but significantly better visualization than EEA alone (44.71° ± 3.24°, p < 0.001). The cMTO corridor provided better instrument maneuverability than the CTM, as evidenced by a significantly greater fencing angle (30.9° ± 4.9°) than with the CTM (21.7° ± 4.02°, p < 0.001). The vertical AoAs for the EEA, cMTO, and CTM corridors were 9.79° ± 1.75°, 10.65° ± 0.82°, and 9.82° ± 1.43°, respectively (p = 0.009), whereas in the horizontal plane, these were 9.29° ± 1.51°, 9.10° ± 0.73°, and 10.49° ± 1.43° (p < 0.001), respectively. Both the CTM and cMTO corridors offered similar areas of surgical freedom (678.06 ± 99.5 mm2 and 673.59 ± 104.8 mm2, p = 0.986), but they were more significant than that provided by the EEA 487.29 ± 112.9 mm2 (p < 0.001). The EEA+cMTO multiport technique may be a better alternative than the EEA+CTM multiport approach for targeting the petroclival region. However, clinical validation is required to confirm these laboratory findings.

OBJECTIVE The endoscopic endonasal approach (EEA) offers direct access to midline skull base lesions, and the anterior transpetrosal approach (ATPA) stands out as a method for granting entry into the upper and middle clival areas. This study evaluated the feasibility of performing EEA for tumors located in the petroclival region in comparison with ATPA. METHODS On 8 embalmed cadaver heads, EEA to the petroclival region was performed utilizing a 4-mm endoscope with either 0° or 30° lenses, and an ATPA was performed under microscopic visualization. A comparison was executed based on measurements of 5 heads (10 sides). Case illustrations were utilized to demonstrate the advantages and disadvantages of EEA and ATPA when dealing with petroclival conditions. RESULTS Extradurally, EEA allows direct access to the medial petrous apex, which is limited by the petrous and paraclival internal carotid artery (ICA) segments laterally. The ATPA offers direct access to the petrous apex, which is blocked by the petrous ICA and abducens nerve inferiorly. Intradurally, the EEA allows a direct view of the areas medial to the cisternal segment of cranial nerve VI with limited lateral exposure. ATPA offers excellent access to the cistern between cranial nerves III and VIII. The quantitative analysis demonstrated that the EEA corridor could be expanded laterally with an angled drill up to 1.8 times wider than the bone window between both paraclival ICA segments. CONCLUSIONS The midline, horizontal line of the petrous ICA segment, paraclival ICA segment, and the abducens nerve are the main landmarks used to decide which approach to the petroclival region to select. The EEA is superior to the ATPA for accessing lesions medial or caudal to the abducens nerve, such as chordomas, chondrosarcomas, and midclival meningiomas. The ATPA is superior to lesions located posterior and/or lateral to the paraclival ICA segment and lesions with extension to the middle fossa and/or infratemporal fossa. The EEA and ATPA are complementary and can be used independently or in combination with each other in order to approach complex petroclival lesions.

Contralateral Transmaxillary Approach to Petrous Apex Granuloma with Lateral Maxillotomy: 2-Dimensional Operative Video

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. 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. 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). 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.

Objectives This study aimed to establish the anatomical landmarks for performing a contralateral transmaxillary approach (CTM) to the petrous apex (PA) and petroclival region (PCR), and to compare CTM with a purely endoscopic endonasal approach (EEA). Design EEA and CTM to the PA and PCR were performed bilaterally in eight human anatomical specimens. Surgical techniques and anatomical landmarks were described, and EEA was compared with CTM with respect to ability to reach the contralateral internal acoustic canal (IAC). Computed tomographic scans of 25 cadaveric heads were analyzed and the "angle" and "reach" of CTM and EEA were measured. Results Entry to the PA via a medial approach was limited by (1) abducens nerve superiorly, (2) internal carotid artery (ICA) laterally, and (3) petroclival synchondrosis inferiorly (Gardner's triangle). With CTM, it was possible to reach the contralateral IAC bilaterally in all specimens dissected, without dissection of the ipsilateral ICAs, pterygopalatine fossae, and Eustachian tubes. Without CTM, reaching the contralateral IAC was possible only if: (1) angled endoscopes and instruments were employed or (2) the pterygopalatine fossa was dissected with mobilization of the ICA and resection of the Eustachian tube. The average "angle" and "reach" advantages for CTM were 25.6-degree greater angle of approach behind the petrous ICA and 1.4-cm more lateral reach. Conclusion The techniques and anatomical landmarks for CTM to the PA and PCR are described. Compared with a purely EEA, the CTM provides significant "angle" and "reach" advantages for the PA and PCR.

Combined Endoscopic Endonasal and Contralateral Transmaxillary Approach for Resection of an Anterior Petrous Chondrosarcoma: A 2-dimensional Operative Video

The endoscopic endonasal approach (EEA) was recently added to the neurosurgical armamentarium as an alternative approach to the petrous apex (PA) region. However, the maximal extension, anatomical landmarks, and indications of this procedure remain to be established. To investigate the limitations and suggest a classification of PA lesions for endoscopic petrosectomy. Five anatomical specimens were dissected with EEA to the PA. Anatomical landmarks for the surgical steps and maximal limits were noted. Pre- and postprocedural computed tomographic scan and image-guidance were used. Relevant surgical cases were reviewed and presented. We defined 3 types of petrosectomy: medial, inferior, and inferomedial. Medial petrosectomy was limited within the paraclival internal carotid artery (ICA) anteriorly, lacerum ICA inferiorly, abducens nerve superiorly, and petrous ICA laterally. Among those, abducens nerve and petrous ICA are surgical limits. Full skeletonization of the paraclival ICA and removal of the lingual process are essential for better access to the medial aspect of PA. Inferior petrosectomy was defined by the lacerum foramen synchondrosis anteriorly, jugular foramen inferiorly, internal acoustic canal posteriorly, and PA superolaterally. Those are surgical limits except for the foramen lacerum synchondrosis. The connective tissue at the pterygosphenoidal fissure was a key landmark for the sublacerum approach. Clinical cases in 3 types of PA lesions were presented. The EEA provides access to the medial and inferior aspects of the PA. Several technical maneuvers, including paraclival and lacerum ICA skeletonization, sublacerum approach, and lingual process removal, are key to maximize PA drilling.

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. 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. 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. 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.

The contralateral transmaxillary (CTM) approach is a new surgical approach that improves the surgical trajectory relative to the petrous segment of the internal carotid artery (ICA). Here, we present our clinical experience with the CTM approach to the petroclival region of the skull base. Retrospective review. A retrospective review of 29 patients who underwent a CTM approach for skull base pathology from 2015 to 2020 was performed. Assessment of gross total resection (GTR) was based on postoperative imaging. The male:female ratio was 15:14, with an average age of 52 years (range = 19-78 years). Diagnoses included: 12 chondrosarcomas, 11 chordomas, two meningiomas, one schwannoma, one metastasis, one petrous apicitis, and one arachnoid cyst. CTM was performed in addition to a transclival approach and ipsilateral transpterygoid approach in all patients. Reconstruction of surgical defects included a vascularized flap in all but two patients: 24 nasoseptal flaps and three lateral nasal wall flaps. The reconstructive flap was on the same side as the CTM approach in 22 of 28 (79%) patients. There were no ICA injuries. In a subset of patients with chondromatous tumors, GTR of the targeted area was achieved in 16 of 22 (73%) evaluable chondromatous tumors. With a median follow-up of 13 months, 64% of these patients are without disease or dead of other causes; the remainder are alive with disease. The CTM approach improves the degree of resection of skull base tumors involving the petroclival region using an endoscopic endonasal approach and may minimize risk to the ICA. 4 Laryngoscope, 131:294-298, 2021.

Introduction: The endoscopic endonasal approach (EEA) has been shown to be a safe and effective means of accessing petrous apex lesions. Lateral lesions can be accessed with extended approaches such as skeletonization and lateralization of the paraclival internal carotid artery (ICA), or a transpterygoid infrapetrous approach. These approaches introduce significant risk to the ICA and are limited to the area immediately posterior to the ICA. This paper studies the feasibility of adding a contralateral transmaxillary corridor (CTM) to provide a more lateral trajectory for access to lateral lesions of the petrous apex with a decreased need for manipulation of the ICA.

The cavernous internal carotid artery (cICA) and its branches can make it challenging to approach the lateral portion of the retrocarotid area of the cavernous sinus (RcACS) and surrounding areas during the endoscopic endonasal approach (EEA). This can sometimes require more invasive transcranial approaches, causing a higher risk of complications. We sought to explore the feasibility of adding a contralateral transmaxillary (CTM) corridor to improve access to the RcACS during EEA. We performed EEA and CTM extensions on 6 cadavers (12 sides) using image guidance. The depth of the surgical corridor, the surgical exposure, the angle of attack, and the trajectory to the anterior genu of the cICA were measured. Two illustrative clinical cases are presented. Compared with the contralateral transnasal approach, the CTM corridor provided a 10.76 (5.32)-mm shorter distance ( P < .001), 36.23% (20.70%) larger surgical exposure ( P < .001), and a 24.6° (3.4°) more parallel trajectory to the anterior genu of the cICA ( P < .001). The mean angle of the lateral nasal wall line and the middle eye line was equal to the mean angle of the contralateral transnasal ( P = .075) and CTM ( P = .262) approaches, respectively. The CTM corridor allowed us to achieve near-total resection of the RcACS and beyond in 2 invasive adenomas with significant lateral extension. The CTM corridor is a feasible addition to standard EEA to access the RcACS and beyond, providing a more medial-to-lateral trajectory and improved access. The middle eye line can be used as a reference to help select patients for this approach.

It is necessary to secure both the proximal and distal sides of the parent artery to prevent premature rupture when clipping cerebral aneurysms. Herein, we describe four cases in which the proximal internal carotid artery (ICA), affected by a paraclinoid aneurysm, was secured using an endoscopic endonasal approach. We used various tools, including a surgical video, cadaver dissection picture, artist's illustration, and intraoperative photographs, to elucidate the process. No patient experienced postoperative complications at our institution. Compared to the cervical or cavernous ICA, the ICA adjacent to the clivus (paraclival ICA) can be anatomically safely and easily exposed using an endoscopic endonasal approach because there is no need to consider cerebrospinal fluid leakage or hemorrhage from the cavernous sinus. Securing the proximal side of the parent artery using an endoscopic endonasal approach may be a viable method for clipping selected ICA aneurysms, such as paraclinoid aneurysms especially for upward or outward aneurysms of the C2 portion.

Endoscopic endonasal approaches to the ventral skull base are categorized based on their orientation in coronal and sagittal planes. For all of these approaches, the sphenoid sinus is the starting point, and provides orientation to important vascular and neural structures. Surgical approaches to the petrous apex include 1) a medial approach, 2) a medial approach with internal carotid artery (ICA) lateralization, and 3) a transpterygoid infrapetrous approach (inferior to the petrous internal carotid artery). The choice of a surgical approach depends on the relationship of the lesion to the internal carotid artery (medial or inferior), degree of medial expansion, and pathology. The purpose of this paper is to discuss the anatomic and technical features of endoscopic surgical approaches to the petrous apex, provide a new classification for approaches that focuses on the relationship of the lesion to the petrous internal carotid artery, and provide outcomes data on our first 20 endoscopic petrous apex approaches. A retrospective clinical outcome study of endoscopic petrous apex surgeries was performed at the University of Pittsburgh Medical Center. The medical records from patients with endoscopic endonasal approaches to isolated petrous apex lesions were reviewed for demographics, diagnoses, presentation, endoscopic approach, and clinical outcomes. Patients with lesions that extended into the petrous apex but were not isolated to the petrous apex were excluded (e.g., clival chordoma with extension into the petrous apex). Twenty patients were included in the analysis: 13 inflammatory cystic lesions (9 cholesterol granulomas and four petrous apicitis) and 7 solid lesions. Chondrosarcoma was the most common solid petrous apex lesion in our series. Twelve of 13 cystic lesions were drained endoscopically (one surgery was aborted early in the series). All drained patients had resolution of presenting symptoms. One patient had closure of the outflow tract without return of symptoms and one patient had revision endoscopic drainage due to scarring and neo-osteogenesis and return of unilateral headache. No carotid injuries and no new cranial neuropathies occurred perioperatively. The advantages and limitations of the medial transsphenoidal approaches (with and without carotid mobilization) and the transpterygoid infrapetrous approach are discussed. The endoscopic endonasal approach to petrous apex lesions is safe and effective for appropriately selected patients in the hands of experienced endoscopic skull base surgeons. If offers advantages of removing the hearing and facial nerve risks from the transtemporal/transcranial approaches and allows for a larger and more natural drainage pathway into the sinuses.