The transnasal approach to the skull base. From sinus surgery to skull base surgery

Management of squamous cell carcinomas of the skull-base

PURPOSE

The purpose of this review is to assess the recent evidence regarding the management of squamous cell carcinoma of the skull-base and to discuss the implications of these findings on clinical practice.

METHOD

Free text Medline and MeSH term search of publications relating to Squamous Cell Carcinoma & Skull-base and Skull base, Neoplasm respectively. Multidisciplinary clinical guidelines were also reviewed.

RESULTS

The primary search yielded a total of 271 papers which following initial review was reduced to 28. Secondary search yielded 56 papers. There were no randomised controlled trials relating to squamous cell carcinoma of the skull-base and as such this review is based on cohort studies, case series and expert opinion.

CONCLUSION

Squamous cell carcinoma (SCC) is the most common cancer occurring in the Head and Neck. Squamous cell carcinoma is also the most common cancer arising within the nose and sinuses of which skull-base squamous cell carcinoma is a rare subgroup. Evidence relating to the management and survival of skull-base SCC is based on expert opinion and. retrospective analyses Clinical examination and biopsy, imaging and a broad multidisciplinary team are key to the management of skull-base SCC. The information gathered should be used to guide informed discussion by suitably trained experts with patients regarding surgical approach, post-operative recovery and adjuvant or neoadjuvant treatments. The standard of care is currently to perform skull base resection with or without additional craniotomy, pedicled or free flap reconstruction in multiple layers and post-operative radiation (usually photons or protons). Open approaches have traditionally been the mainstay, however in certain cases endoscopic approaches can yield equivalent results and offer many advantages. Despite advances in care survival remains poor with a nearly one in five risk of nodal recurrence within two years.

[An anatomical study on the applicability of direct endoscopic exclusion of the ethmoid arteries for devascularization of the anterior skull base structures]

The anterior skull base structures are the site of initial growth of histologically different tumors. The difficulties in their removal are often associated with significant vascularization, which may limit the amount of resection due to abundant intraoperative blood loss. Midline tumors are primarily fed by the ethmoid arteries that are not accessible to embolization. The aim of this work was a comparative experimental study of various direct approaches to the ethmoid arteries.

MATERIAL AND METHODS

The study was conducted on anatomical specimens of 12 cadaveric heads of deceased people without pathology of the anterior skull base structures, orbits, nasal cavity, and paranasal sinuses (24 sides). In all specimens, the internal and external carotid arteries were stained with silicone. During anatomical dissection, four surgical approaches for exclusion of the ethmoid arteries were studied: 1) transorbital approach to the arteries using a bicoronal incision; 2) endoscopic retro-caruncular approach; 3) endoscopic endonasal transethmoidal approach to the ethmoid artery canals; 4) endoscopic endonasal transethmoidal transorbital approach to the ethmoid arteries in the orbit.

RESULTS

We described a surgical technique for exclusion of the ethmoid arteries using the approaches and analyzed their advantages and disadvantages. We formulated an algorithm for choosing the method for direct endoscopic exclusion of the ethmoid arteries, depending on the surgical approach chosen for removal of the tumor and features of the tumor extracranial spread.

CONCLUSION

The decision on tumor devascularization is based on assessment of tumor blood supply (CT angiography or MR angiography data). Our study demonstrated the advantages and disadvantages of various approaches to the ethmoid arteries for their exclusion in order to early devascularize anterior skull base tumors. All these approaches are less traumatic and characterized by a good cosmetic and functional outcome.

[Biopsy and resection of skull base tumors using transorbital endoscopic approaches: primary results]

AIM

Transorbital neuroendoscopic surgery is a new skull base surgery technique that uses the orbit as an artificial corridor to the anterior and middle skull base. The space is created between the periorbita and orbital walls by their additional resection and gentle traction of the orbital contents. Skull base structures are reached using cosmetic incisions. The major advantages of transorbital endoscopic approaches include their variety, possibility of their combination, and access to the central and lateral skull base lesions. The aim of this study was to analyze the primary results of transorbital endoscopic biopsy and resection of skull base lesions, which were performed at the N.N. Burdenko National Medical Research Center for Neurosurgery (Moscow, Russia).

MATERIAL AND METHODS

In 2017-2018, the authors operated on 12 patients with skull base lesions using transorbital endoscopic approaches. The series included ten female and two male patients. The patient's age varied between 24 and 78 years. All patients were admitted for the first time. Half of them underwent biopsy, while the other half underwent tumor resection. The upper-lateral transorbital approach with an eyebrow incision was used in most (8/12) patients; the retrocaruncular approach was used in two cases; the lateral retrocanthal approach was applied in one case; the upper-medial approach with an eyebrow incision was used in one patient.

RESULTS

The histological diagnosis was established in all six biopsies: 3 pseudotumors, 2 WHO Grade I meningiomas, and 1 clear-cell kidney cancer. Tumor resection was successful in 5 out of 6 patients; repeated surgery was required in one patient. In one case, the transorbital approach was combined with the transnasal one for treatment of supraorbital mucocele. One patient developed a persistent neurological deficit (dysfunction of the fifth and sixth nerves) after upper-lateral transorbital surgery. There were no poor cosmetic results in the series.

CONCLUSION

Transorbital neuroendoscopic surgery needs an interdisciplinary approach and a sufficient amount of surgical experience. Surgical skills setting includes microsurgical and endoscopic tumor resection, harvesting and positioning of free and vascularized grafts for skull base reconstruction and prevention of postoperative enophthalmos, and facial incisions and their cosmetic closure. Implementation of new local vascularized flaps may significantly improve the results of transorbital endoscopic procedures and extend the spectrum of indications.

Modified Anterior Craniofacial Osteotomy Using Partial Nasal Bone Division and Reconstruction in Frontoethmoidal Sinus Meningioma

Typical transcranial approaches are insufficient for adequate visualization and resection of skull base tumors. Different approaches with multiple modifications have been attempted. Here, we describe a new approach for a lesion that is central and hard to treat by conventional craniotomy and successful reconstruction with calvarial bone graft and titanium mesh plate. A 69-year-old female patient presented with recurrent meningioma. The tumor had invaded the frontal lobe, right supraorbital rim, and ethmoidal bone. We performed a modified anterior craniofacial approach that fully exposed the tumor and invaded bone. In consideration of the patient's age and cosmetic result, the tumor and invaded bone was resected and the defect area was reconstructed with titanium mesh and calvarial bone graft. At 6 months postoperative the patient had no complications and was satisfied with the esthetic result. We report this case to demonstrate the successful approach and reconstruction using this technique.

[Choosing an anterior midline approach to skull base tumors]

The purpose of this review is to analyze used anterior midline approaches to the skull base, identify their advantages and disadvantages, and, after reviewing the literature data, submit a developed algorithm for choosing an optimal approach to the approval of colleagues. We provide brief information on approach techniques, indications and contraindications, and advantages and disadvantages as well as analyze international experience of using the discussed approaches. On the basis of literature data, we have developed a prototype algorithm for choosing an optimal approach to medial tumors of the anterior skull base. The situation of choosing an optimal approach reveals the absence of a clear understanding of the boundaries between capabilities and limitations of approaches. To solve this problem, an original prospective study is required.

Endoscopic skull base training using 3D printed models with pre-existing pathology

Endoscopic base of skull surgery has been growing in acceptance in the recent past due to improvements in visualisation and micro instrumentation as well as the surgical maturing of early endoscopic skull base practitioners. Unfortunately, these demanding procedures have a steep learning curve. A physical simulation that is able to reproduce the complex anatomy of the anterior skull base provides very useful means of learning the necessary skills in a safe and effective environment. This paper aims to assess the ease of learning endoscopic skull base exposure and drilling techniques using an anatomically accurate physical model with a pre-existing pathology (i.e., basilar invagination) created from actual patient data. Five models of a patient with platy-basia and basilar invagination were created from the original MRI and CT imaging data of a patient. The models were used as part of a training workshop for ENT surgeons with varying degrees of experience in endoscopic base of skull surgery, from trainees to experienced consultants. The surgeons were given a list of key steps to achieve in exposing and drilling the skull base using the simulation model. They were then asked to list the level of difficulty of learning these steps using the model. The participants found the models suitable for learning registration, navigation and skull base drilling techniques. All participants also found the deep structures to be accurately represented spatially as confirmed by the navigation system. These models allow structured simulation to be conducted in a workshop environment where surgeons and trainees can practice to perform complex procedures in a controlled fashion under the supervision of experts.

Robotic surgery for the sinuses and skull base: what are the possibilities and what are the obstacles?

PURPOSE OF REVIEW

Robotic surgery in otolaryngology - head and neck surgery has become a valuable tool in certain anatomic approaches; however, its application in surgery of the paranasal sinuses and anterior skull base is still in an investigatory phase and requires further evaluation.

RECENT FINDINGS

Existing robotic surgical systems face particular limitations in their application at the skull base because of instrument size and lack of variability. Unfortunately, only one system is available commercially that is applicable in the head and neck region and FDA approved for use in patients. This system, although advantageous in many otolaryngologic procedures, is difficult to use for endoscopic sinus and skull base surgery. However, other systems that target this anatomic subsite specifically are in development and show promise. Advances in the design of robotic arms, materials, and shape will potentially give surgeons a significant advantage over traditional endoscopic techniques.

SUMMARY

This article will review the current applications of robotic systems in paranasal sinus and skull base surgery, describe the requirements of a robotic system for use in this type of surgery, and describe a system under development at our institution.