Modified endoscopic endonasal approach with a minimally invasive transoral approach-an adjunct to infrapetrous approaches

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.

Endoscopic trans-lateral oropharyngeal wall approach to the petrous apex and the petroclival region

BACKGROUND

A trans-lateral oropharyngeal wall approach (TLOWA) to the petrous apex has not been previously defined. This study aims to assess the feasibility of a TLOWA for surgical access to the petrous apex and the petroclival region.

METHODS

An endoscopic TLOWA for exposure of the petrous apex and petroclival region was performed on five cadaveric specimens (10 sides). Associated anatomical landmarks were defined, and the strategies for maximal exposure of the internal carotid artery (ICA) were explored.

RESULTS

Via a TLOWA, the parapharyngeal ICA was widely exposed in all 10 sides. Following transection of the Eustachian tube, the inferior petrous apex and petroclival region could be sufficiently exposed. After drilling the anteroinferior bony canal, the horizontal petrous ICA, foramen lacerum, and the paraclival ICA could be adequately revealed.

CONCLUSION

The TLOWA may provide an alternative corridor for access to the petrous apex and the petroclival region. The parapharyngeal, petrous, lower paraclival ICAs, and the foramen lacerum could be adequately exposed via the TLOWA.

Endoscopic Endonasal Approach to the Pterygopalatine Fossa and Infratemporal Fossa: Comparison of the Prelacrimal and Denker's Corridors

BACKGROUND

Both the endoscopic transnasal Denker's and prelacrimal approaches provide surgical access to the pterygopalatine fossa (PPF) and infratemporal fossa (ITF).

OBJECTIVES

This study compares the potential maximum exposure of the PPF and ITF and quantifies the difference in surgical freedom via endoscopic Denker's and prelacrimal approaches.

METHODS

Six cadaveric specimens (12 sides) were dissected using a prelacrimal approach on one side and an endoscopic Denker's approach on the contralateral side. The contents of the PPF and ITF were sequentially exposed. Surgical freedom for each corridor was subsequently calculated.

RESULTS

This study confirms that both the prelacrimal and Denker's approaches provide adequate exposure of the PPF and ITF. The maximum exposure boundaries were similar for both approaches, including the middle cranial fossa superiorly, floor of the maxillary sinus inferiorly, zygomatic arch and temporomandibular joint laterally, and post-styloid space posteriorly. However, the data revealed a statistically significant difference (p < 0.05) regarding the surgical freedom of the prelacrimal (388.17 ± 32.86 mm²) and the endoscopic Denker's approaches (906.35 ± 38.38 mm²).

CONCLUSION

When compared with an endoscopic Denker's approach, a prelacrimal approach seems to achieve a similar extent of exposure (ie, visualization) of the PPF and ITF. Nonetheless, the endoscopic Denker's approach offers superior surgical freedom; thus, it is preferred for the management of complex lesions which requires increased instrument maneuverability with a 3- or 4-handed technique.

Role of resection of torus tubarius to maximize the endonasal exposure of the inferior petrous apex and petroclival area

Endoscopic access to the petrous apex and petroclival region often requires sacrificing the Eustachian tube (ET). This study aimed to compare the maximum exposure of the petrous apex and petroclival region via an endonasal corridor when sparing or resecting the ET and its torus. Six cadaveric specimens (12 sides) were dissected through an endonasal transpterygoid approach. Endonasal exposure of the petroclival region was completed using techniques that included the preservation of the ET (group 1), resection of the torus tubarius (group 2), and resection of the ET (group 3) were sequentially performed on each side. The working distances from the anterior genu of the petrous internal carotid artery (ICA) to the inferior boundaries of each corridor were measured and compared. In group 1, the medial petrous apex and petroclival sulcus could be exposed with a working distance of 4.08 ± 0.67 mm. In group 2, the fossa of Rosenmüller, inferior petrous apex, and hypoglossal canal could be exposed, with a significantly increased working distance of 18.33 ± 0.89 mm (P = .001). In group 3, the exposure and ICA control was superior and offered a working distance of 20.67 ± 0.78 mm. No statistically significant difference derived from comparing groups 2 and 3 (P = .875). Resection of the torus tubarius can increase exposure of the petrous apex and petroclival region. It provides an alternative to resecting the ET, which might be beneficial for maintenance of middle ear function. ET resection, however, seems superior when ICA control is required.

Endoscopic transoral nasopharyngectomy

BACKGROUND

A minimal access technique for the management of nasopharyngeal tumors extending below the palatal plane and laterally beyond the pterygoid musculature is yet to be developed. In this study we demonstrate the feasibility of endoscopic transoral nasopharyngectomy (ETON) for resection of large nasopharyngeal lesions as a natural orifice alternative to traditional approaches.

METHODS

ETON was completed in three latex-injected specimens. Surgical freedom (SF) and angles of attack (AoA) were calculated along the internal carotid artery (ICA).

RESULTS

An endoscopic transoral approach was successfully used to identify the parapharyngeal ICA and subsequently perform a complete nasopharyngeal resection. SF and AoA (sagittal) were found to be the greatest at the anterior genu of the ICA.

CONCLUSIONS

ETON is feasible. It provides wide exposure of the skull base and proximal control of the ICA. It may be indicated for the management of nasopharyngeal tumors with inferolateral extension, involving the ICA.

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.

Ventilated Upper Airway Endoscopic Endonasal Procedure Mask: Surgical Safety in the COVID-19 Era

BACKGROUND

COVID-19 poses a risk to the endoscopic skull base surgeon. Significant efforts to improving safety have been employed, including the use of personal protective equipment, preoperative COVID-19 testing, and recently the use of a modified surgical mask barrier.

OBJECTIVE

To reduce the risks of pathogen transmission during endoscopic skull base surgery.

METHODS

This study was exempt from Institutional Review Board approval. Our study utilizes a 3-dimensional (3D)-printed mask with an anterior aperture fitted with a surgical glove with ports designed to allow for surgical instrumentation and side ports to accommodate suction ventilation and an endotracheal tube. As an alternative, a modified laparoscopic surgery trocar served as a port for instruments, and, on the contralateral side, rubber tubing was used over the endoscrub endosheath to create an airtight seal. Surgical freedom and aerosolization were tested in both modalities.

RESULTS

The ventilated mask allowed for excellent surgical maneuverability and freedom. The trocar system was effective for posterior surgical procedures, allowing access to critical paramedian structures, and afforded a superior surgical seal, but was limited in terms of visualization and maneuverability during anterior approaches. Aerosolization was reduced using both the mask and nasal trocar.

CONCLUSION

The ventilated upper airway endoscopic procedure mask allows for a sealed surgical barrier during endoscopic skull base surgery and may play a critical role in advancing skull base surgery in the COVID-19 era. The nasal trocar may be a useful alternative in instances where 3D printing is not available. Additional studies are needed to validate these preliminary findings.

Surgical approaches to the petrous apex

The petrous apex is a difficult to reach surgical area due to its deep position in the skull base and many vital surrounding structures. Petrous apex pathology ranges from extradural cholesterol granulomas, cholesteatomas, asymmetric pneumatization, and osteomyelitis to intradural meningiomas and schwannomas. Certain lesions, such as cholesterol granulomas, can be managed with drainage while neoplastic lesions must be completely resected. Surgical options use open, endoscopic, and combined techniques and are categorized into anterior, lateral, and posterior approaches. The choice of approach is determined by the nature of the pathology and location relative to vital structures and extension into surrounding structures and requires thorough preoperative evaluation and discussion of surgical goals with the patient. The purpose of this state-of-the-art review is to discuss the most commonly used surgical approaches to the petrous apex, and the anatomy on which these approaches are based.