Endoscope-assisted contralateral transmaxillary approach to the clivus and the hypoglossal canal: technical case report

Contralateral Nasofrontal Trephination: A Novel Corridor for a "Dual Port" Approach to the Petrous Apex

BACKGROUND AND OBJECTIVES

Expanded endonasal approaches (EEAs) have proven safe and effective in treating select petrous apex (PA) pathologies. Angled endoscopes and instruments have expanded indications for such approaches; however, the complex neurovascular anatomy surrounding the petrous region remains a significant challenge. This study evaluates the feasibility, anatomic aspects, and limitations of a contralateral nasofrontal trephination (CNT) route as a complementary corridor improving access to the PA.

METHODS

Expanded endonasal and CNT approaches to the PA were carried out bilaterally in 15 cadaveric heads with endovascular latex injections. The distance to the PA, angle between instruments through the 2 approach portals, and surgical freedom were measured and compared.

RESULTS

Three-dimensional DICOM-based modeling and visualization indicate that the CNT route reduces the distance to the target located within the contralateral PA by an average of 3.33 cm (19%) and affords a significant increase in the angle between instruments (15.60°; 54%). Furthermore, the vertical vector of approach is improved by 28.97° yielding a caudal reach advantage of 2 cm. The area of surgical freedom afforded by 3 different approaches (endonasal, endonasal with an endoscope in CNT portal, and endonasal with an instrument in CNT portal) was compared at 4 points: the dural exit point of the 6th cranial nerve, jugular foramen, foramen lacerum, and petroclival fissure. The mean area of surgical freedom provided by both approaches incorporating the CNT corridor was superior to EEA alone at each of the surgical targets ( P = <.001).

CONCLUSION

The addition of a CNT portal provides an additional avenue to expand on the classical EEA to the PA. This study provides insight into the anatomic nuances and potential clinical benefits of a dual-port approach to the PA.

Comparative Anatomy of the Contralateral Transmaxillary Approach Alone and With Ipsilateral Transpterygoid Extension: Quantitative Insights on Surgical Exposure and Maneuverability in the Petroclival Region

BACKGROUND AND OBJECTIVES

Beyond qualitative evidence legitimizing endoscopic corridors through contralateral transmaxillary (CTM) and endonasal ipsilateral transpterygoid (ITP) corridors to the petrous apex and petroclival region, surgical feasibility by direct quantitative comparative anatomy is sparse. Our cadaveric study addresses this by performing the CTM approach followed by ITP extension to quantify the extent of petrous apex resection, instrument maneuverability, and working distance to petrous apex.

METHODS

Anatomic dissections were performed bilaterally on 5 latex-injected human cadaveric heads (10 petrous bones). After CTM dissections were quantified, the ITP approach was added enlarging initial exposure. Differences were measured with statistical significance when P values are < .05.

RESULTS

The mean petrosectomy volume was 0.958 cm3 with CTM and 1.987 cm3 with CTM + ITP, corresponding to 14.53% and 30.52% petrous apex resection, respectively. Craniocaudal instrument mobility was more limited in the lateral extent of dissection compared with the midline for both CTM (8.062° vs 14.416°) and CTM + ITP (5.4° vs 14.4°). The CTM approach achieved the lateral-most dissection at the body of the petrous apex (15.936 mm), with lateralization more limited in the superior petroclival region (9.628 mm) and the inferior petroclival region (8.508 mm). Angle of surgical maneuverability increased superiorly vs inferiorly in the CTM approach (mean 12.596° vs 8.336°, respectively). The CTM approach offered the shortest mean working distance (88.624 mm) to the petroclival region compared with the bi-nares approach (100.5 mm). CTM + ITP achieved greater lateralization in the superior (21.237 mm) and inferior (22.087 mm) aspects of the petroclival region compared with the CTM approach.

CONCLUSION

Operative considerations are discussed in accessing target neurovascular structures through the uniquely shaped corridors formed by the CTM or combined CTM + ITP. Allowing mobilization of the internal carotid artery laterally and eustachian tube inferiorly, addition of the ITP allowed for larger petrosectomy than CTM alone, especially in the inferior and lateral aspects of the petrous bone.

Combined Endoscopic Endonasal Transclival and Contralateral Transmaxillary Approach to the Petrous Apex and the Petroclival Synchondrosis: Working "Around the Corner" of the Internal Carotid Artery-Quantitative Anatomical Study and Clinical Applications

The endoscopic contralateral transmaxillary (CTM) approach has been proposed as a potential route to widen the corridor posterolateral to the internal carotid artery (ICA). In this study, we first refined the surgical technique of a combined multiportal endoscopic endonasal transclival (EETC) and CTM approach to the petrous apex (PA) and petroclival synchondrosis (PCS) in the dissection laboratory, and then validated its applications in a preliminary surgical series. The combined EETC and CTM approach was performed on three cadaver specimens based on four surgical steps: (1) the nasal, (2) the clival, (3) the maxillary and (4) the petrosal phases. The CTM provided a "head-on trajectory" to the PA and PCS and a short distance to the surgical field considerably furthering surgical maneuverability. The best operative set-up was achieved by introducing angled optics via the endonasal route and operative instruments via the transmaxillary corridor exploiting the advantages of a non-coaxial multiportal surgery. Clinical applications of the combined EETC and CTM approach were reported in three cases, a clival chordoma and two giant pituitary adenomas. The present translational study explores the safety and feasibility of a combined multiportal EETC and CTM approach to access the petroclival region though different corridors.

Contralateral Transmaxillary Corridor Used in Endoscopic Endonasal Approach for Resecting Adenoma Invading the Retrocarotid Area of the Cavernous Sinus and Beyond: Surgical Anatomy, Patient Selection Algorithm, and Illustrative Cases

BACKGROUND AND OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Chondrosarcoma of the petrous apex with nerve abducens involvement in a woman with pre-existing contralateral amblyopia

We report about a case of a woman in her 50s with a chondrosarcoma of the petrous apex. She has a strabism due to a right-sided amblyopia since childhood and noticed a slowly progressive squint angle in the last months. Her general practitioner (GP) referred her to an ophthalmologist who diagnosed a left abducens paresis and initiated an MRI demonstrating a mass in the left petrous apex. A transnasal endoscopic transsphenoidal biopsy revealed a grade I chondrosarcoma. The patient underwent an endoscopic transsphenoidal anterior petrosectomy approach with complete removal of the tumour. After surgery the squint angle gradually improved to previous levels, so that the patient was able to resume her work. This report demonstrates that even slight changes of a squint angle without diplopia, in this case because of pre-existing amblyopia, could be a hallmark of an intracranial process.

Endoscopic Approaches to the Paramedian Skull Base: An Anatomic Comparison of Contralateral Endonasal and Transmaxillary Strategies

BACKGROUND

The expanded endoscopic endonasal approach (EEA) is limited laterally by the internal carotid artery (ICA). The EEA to the paramedian skull base often requires complex maneuvers such as dissection of the Eustachian tube (ET) and foramen lacerum (FL), and ICA manipulation. An endoscopic contralateral transmaxillary approach (CTMA) has the potential to provide adequate exposure of the paramedian skull base while bypassing manipulation of the aforementioned anatomic structures.

OBJECTIVE

To quantify and compare the surgical nuances of a CTMA and a contralateral EEA when approaching the paramedian skull base in cadaveric specimens.

METHODS

Five adult cadaveric heads were dissected bilaterally (10 sides) using a contralateral EEA and a CTMA to expose targets of interest at the paramedian skull base. For each target in both approaches, the surgical freedom, angle of attack, the corridor's "perspective angle," and "turning angle" to circumvent the ICA, ET, and FL were obtained.

RESULTS

The CTMA achieved superior surgical freedom at all targets ( P < .05) except at the root entry point of cranial nerve XII. The CTMA provided superior vertical and horizontal angles of " attack " to the majority of targets of interest. Except when approaching the root entry point of cranial nerve XII, the CTMA " turning angle " around the ICA, ET, and FL were wider with CTMA for all targets.

CONCLUSION

A CTMA complements the EEA to access the paramedian skull base. A CTMA may limit the need for complex maneuvers such as ICA mobilization and dissection of the ET and FL when approaching the paramedian skull base.

Expanded endoscopic endonasal transsphenoidal approach to determine morphological characteristics and clinical considerations of the cavernous sinus venous spaces

The study aimed at investigating the morphological characteristics and interconnected regularities of the cavernous sinus (CS) venous spaces using an expanded endoscopic endonasal transsphenoidal approach. Surgical dissections were performed for 15-colored silicon-injected human head specimens. The CS venous spaces were examined for their morphological and clinical characteristics using an expanded endoscopic endonasal transsphenoidal approach. The intracavernous course of the internal carotid artery (ICA) divided the CS venous spaces into four interconnected virtual compartments: medial, anteroinferior, posterosuperior, and lateral. The CS venous spaces had peculiar morphological characteristics; the medial compartment was C-shaped while the anteroinferior compartment resembled a boat's bow. The mean distances from the medial border of the inferior horizontal segment of cavernous ICA to the mid-line of the pituitary gland (PG) were 6.07 ± 1.61 mm (left) and 5.97 ± 1.89 mm (right); the mean distances from the medial border of the subarachnoid segment of cavernous ICA to the mid-line of the PG were 5.77 ± 1.16 mm (left) and 5.63 ± 1.17 mm (right); the mean distances from the medial border of the anterior vertical segment of cavernous ICA to the mid-line of the PG were 10.27 ± 1.74 mm (left) and 10.47 ± 1.90 mm (right). Morphological characteristics and the knowledge of the interconnected regularities of the CS venous spaces may help surgeons accurately locate the neurovascular structure, and thus may contribute to the effective prediction of tumor invasion and extension during endoscopic CS surgery.

How I do it? Resection of residual petrous apex chordoma with combined endoscopic endonasal and contralateral transmaxillary approaches

BACKGROUND

The petrous apex is one of the most challenging areas of the skull base to access.

METHOD

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.

CONCLUSION

This case demonstrates the value of the CTM corridor in resecting petrous apex lesions that are posterolateral to the paraclival segment of the ICA.

Maximal Resection of Tumors Encasing the Internal Carotid Artery and Hindering Internal Carotid Artery Expansion Followed by Revascularization Surgery: A Series of Nine Cases at a Single Tertiary Center

Purpose

Cerebral reconstruction appears to play a diminished role in managing complex skull base tumors involving vital neurovascular structures.

Materials and Methods

Patients with recurrent or progressive middle cranial fossa tumors treated by radical resection followed by extracranial-to-intracranial (EC-IC) bypass from 2014 to 2019 were included. Balloon test occlusion (BTO) was performed preoperatively.

Results

Overall, 9 patients (5 males, 4 females; mean age, 29.9 years) were enrolled. The lesions arose from the parasellar region (3), cavernous sinus (3), petroclival region (2), or orbital apex (1), and all encased the cavernous/petrous portion of the internal carotid artery. Before tumor resection, internal maxillary artery (IMA) bypass was performed for 7 patients, cervical EC-IC bypass was performed for 1 patient, and interposed superficial temporal artery (STA) bypass was performed for 1 patient. BTO failed in 8 patients and was tolerated by one patient. Intraoperative blood flow of the interposed graft was 79.7 ± 37.86 ml/min after IMA bypass, 190.6 ml/min following cervical EC-IC bypass and 75 ml/min after interposed STA bypass. All bypasses were patent on intraoperative indocyanine green angiography. Radical tumor resection was achieved in 5 patients (55.6%), and patency was confirmed postoperatively in 88.8% (8/9) of bypasses. Six patients showed favorable outcomes at discharge. At the 2-year follow-up, 7 patients (77.8%) had favorable outcomes (Karnofsky Performance Scale score&gt;80). At the 1.5-year follow-up, one patient had died due to infarction; at the 3-year follow-up, another patient had developed tumor recurrence despite being asymptomatic.

Conclusion

Cerebral bypass remains a vital tool for managing select middle cranial fossa tumors that invade or erode the surrounding neurovasculature or hinder carotid artery expansion and are difficult to resect.

Anatomical Limits of the Endoscopic Contralateral Transmaxillary Approach to the Petrous Apex and Petroclival Region

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.

Experience With the Endoscopic Contralateral Transmaxillary Approach to the Petroclival Skull Base

OBJECTIVES/HYPOTHESIS

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.

STUDY DESIGN

Retrospective review.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:294-298, 2021.