There is no single optimal approach for all skull base pathologies and locations. Skull base surgeons must tailor their surgery to both the tumor and the goals of care for the patient to optimize conditions for tumor removal while minimizing morbidity. Lateral skull base approaches are an attractive option to access the skull base given the direct surgical access to the lower cranial nerves, the intra- and extratemporal internal carotid artery (ICA), and the venous sinuses. These approaches can be broadly classified as otic capsule-sparing and otic capsule-sacrificing. These approaches are complex in nature, and patient selection on a case-by-case basis with multidisciplinary input is essential. Complex skull base tumors may not be adequately addressed with a single surgical approach and may require a combination or modification of these techniques. In this chapter, we will describe transcochlear approaches and how they can be modified to provide extended skull base access.

Traditionally, two approaches have been utilized to access the rostral basilar artery (BA) for clipping aneurysms. These are: 1) the subtemporal approach pioneered by Canadian neurosurgeon Charles George Drake and 2) the transsylvian or pterional approach popularized by Turkish neurosurgeon Mahmut Gazi Yasargil. Both of these approaches have assets and liabilities, and both have modifications to expand the surgical field of view. Some rostral BA aneurysms and some patients with aneurysms of both the anterior and posterior circulation requiring clip ligation may benefit from a combined transsylvian and subtemporal (half-and-half) exposure. In this chapter, we describe our version of that approach, which provides access to both anterior and posterior circulation aneurysms. We detail neuroanesthesia considerations, patient positioning, bone drilling, subarachnoid dissection, and clip placement. Also included is an illustrative case.

Skull base tumors are often intimately involved with critical vascular structures, which can be a barrier to maximal resection. In these cases, cerebral revascularization, including vascular bypass, can be an important adjunct technique. The feasibility of bypass depends on patient history, the anticipated tumor pathology, and characteristics of the cerebral vasculature. These procedures require considerable experience and expertise, and their indications must be well considered before performing them. A number of imaging and interventional studies can help establish the utility and feasibility of bypass preoperatively. Emerging technologies will help to refine the indications and streamline the performance of these challenging procedures. Here, we discuss the historical basis of bypass in skull base tumor surgery, indications in the modern era, the microanatomy of common bypasses, patient selection, and endovascular options for revascularization.

Combined approaches are often necessary to address large or invasive skull base pathology. A combined suboccipital craniotomy and neck dissection is often utilized for invasive posterior fossa skull base tumors and neck tumors. Management of these tumors often requires the collaboration of multiple specialties. Tumors in this location are often intimately involved with important neurovascular structures. Good pre-operative evaluation, intra-operative monitoring, and closely monitored post-operative care are essential. The extent of resection and goals of care depends on a case-by-case analysis including the patient’s age, the aggressiveness of the tumor pathology, presenting symptoms, and comorbidities. This chapter reviews the indications, anatomy, and surgical nuances of this complex approach.

Access to the craniovertebral junction has traditionally been obtained by utilizing transoral approaches; however, the nasal corridor is a useful alternative for direct access to the craniovertebral junction with decreased morbidity. The inferior extent of the endonasal approach is limited by the palate and nasal bones and when this is reached, the caudal extent can be expanded with the combined endonasal-transoral approach. The addition of the transoral corridor allows more caudal access and allows for more complex reconstructions. In this chapter, we discuss a step-wise approach to planning for surgical access of the craniovertebral junction.

It has been well established that surgical resection in patients with singular symptomatic brain metastases prolongs survival. However, surgical resection for patients with multiple symptomatic brain metastases is less commonly performed and reported in the literature, and even avoided, for a multitude of reasons. However, the advent of minimally invasive keyhole techniques has allowed for an increased survival benefit from simultaneous resections of multifocal or multiple lesions, without increasing morbidity. These keyhole techniques have improved the quality of life in patients with multiple lesions by increasing the total extent of resection, which has been shown to correlate with overall patient survival, while minimizing recovery and morbidity. This chapter details the patient selection criteria, preoperative planning, surgical technique, steps for complication avoidance, and postoperative considerations necessary for developing an appropriate treatment plan utilizing multiple keyhole craniotomies in a single surgical setting.

Neurosurgical lesions that span the supratentorial and infratentorial compartments can pose a significant challenge. Although these lesions are traditionally addressed using transpetrosal approaches, skull base principles can be maintained and successful resection achieved with the combination of less extensive surgical approaches. Through the combination of the orbitozygomatic and retrosigmoid approaches, the vast majority of anterior, middle, and posterior fossa pathology can be successfully resected. Over the past two decades at our institution, the orbitozygomatic and retrosigmoid approaches have largely replaced the more traditional transpetrosal approaches, with the combined two-stage orbitozygomatic-plus-retrosigmoid approach being utilized when necessary.

Numerous areas of skull base neurosurgery and interventional neuroradiology overlap. Interventional neuroradiology techniques can often be employed in combination with open skull base surgery to provide solutions to complex cerebrovascular and oncological problems. This chapter describes the indications for, and technical nuances of, combined microsurgical and endovascular treatment of cerebrovascular and skull base disease. In particular, three major disease states are discussed: intracranial aneurysms, arteriovenous malformations of the brain and dura, and skull base tumors.

Orbitofrontal craniotomy with direct orbitotomy gives broad surgical access to the anterior cranial fossa and orbit. Indications for this combined technique vary and are dependent on the location and nature of the lesion. This technique can also be used for orbital decompression in severe cases of Graves’ orbitopathy. A complete clinical history with imaging is critical for preoperative planning. Postoperatively, close monitoring of vision and neurological status is critical to identifying and preventing complications.

One of the most common combined approaches to skull base tumors includes a transcranial and endoscopic endonasal approach to the anterior and central skull base. Independently these are two common operative procedures employed in the modern treatment of skull base lesions, and have been favored over other historical approaches such as craniofacial, transfacial, and midface degloving due to decreased morbidity and mortality. When these approaches are combined, they add a new solution to the neurosurgeon’s armamentarium, providing a relatively minimally invasive approach with maximal resection in indicated complex lesions.

Traditionally, lesions communicating between the middle fossa or supratentorial cisterns and the posterior fossa have been addressed by middle fossa approaches with the addition of a traditional anterior petrosectomy, or alternatively presigmoid approaches incorporating a posterior petrosectomy. Alternatively, when global access is needed a combined petrosal approach may be used. These approaches have advantages and disadvantages that those using them frequently are well acquainted with, and will be covered elsewhere in this book. However, a less utilized approach that takes full advantage of the familiarity and relative ease of a retrosigmoid operation is the addition of a suprameatal boney removal (we euphemistically call this the reverse petrosectomy) in select cases, which minimizes approach-related morbidity and dissection. Further, an endoscope can be used to augment visualization previously accomplished with boney removal necessitated by the straight line of sight inherent to the microscope. Here we describe this technique in detail, taking advantage of a component-based approach to the skull base.

Optimal treatment for vestibular schwannomas has long been a debated topic in skull base surgery. Advancements in surgical technique and adjuncts, as well as radiation therapy, have further confounded what is considered the optimal treatment regimen. Goals of care have focused on maximal tumor resection and avoidance of cranial neuropathies. Treatment options continue to include surveillance imaging with close observation, microsurgical resection, and radiotherapy (either with stereotactic radiosurgery or hypofractionated treatments). This chapter reviews the current management options, with a focus on the development of hybrid strategies for the treatment of these challenging tumors.

Lesions requiring resection in the posterior mediobasal temporal or adjacent occipital lobe can be difficult to access surgically. An extra-axial supracerebellar approach utilizing an opening in the tentorium can be accomplished through a keyhole suboccipital paramedian craniotomy to give the surgeon adequate exposure to address lesions in this location. Herein we describe the keyhole technique for a supracerebellar-transtentorial approach to posterior mediobasal temporal lesions and the associated benefits, challenges, and clinical pearls.

The combined endoscopic endonasal, transethmoidal, transcribriform approach with endoscope-assisted supraorbital craniotomy is a minimally invasive approach that can be used as an alternative to the classic transcranial, transfacial, or combined craniofacial approaches to lesions of the anterior cranial fossa. This approach is best used for lesions that extend anteriorly to the frontal sinus, laterally beyond the lamina papyracea, and inferiorly into the ethmoid sinus. This chapter details the approach as well as closure of the combined endoscopic endonasal, transethmoidal, transcribriform approach with endoscope-assisted supraorbital craniotomy.

Lateral skull base meningoencephalic herniations (MEH) are rare instances where dura mater (meningocele) or cerebral tissue (encephalocele) protrudes through skull base dehiscences, commonly in the tegmen tympani or mastoidium. Encephaloceles and cerebrospinal fluid (CSF) leaks carry great risk, as they provide a potential pathway from the middle ear to the subarachnoid space. Patients often present with non-specific clinical symptoms, so a high degree of clinical suspicion is needed, with a thorough radiologic assessment to confirm the diagnosis and location of bony defects. Early detection and surgical repair of encephaloceles or CSF leaks are imperative. Typical surgical approaches for lateral skull base encephaloceles are based on surgeon experience and include the transmastoid (TM), middle cranial fossa (MCF), and combined TM and MCF approach. In general, the TM approach is used for small defects, and for larger defects, the MCF or combined approach is typically the procedure of choice. When there is no possibility of hearing preservation or rehabilitation, a middle ear obliteration (MEO) can be considered as it has very low recurrence rates and provides definitive treatment. Our institution prefers the combined transmastoid and keyhole middle cranial fossa approach.