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.

It is often necessary to use more than one skull base approach for the treatment of complex lesions to maximize resection and minimize morbidity and mortality. The advent of widespread endoscope use has increased the armamentarium for skull base surgeons to tackle these dangerous tumors and lesions. A combined endoscopic transnasal and simultaneous transorbital approach allows for minimally invasive multiportal surgery to reach difficult-to-access skull base regions with minimal collateral damage. Multiple surgical trajectories can be readily and safely obtained in a minimally invasive manner. The use of standard zero-degree endoscopes via this approach allows for easier and safer manipulation of the target lesion. In this way, multistage or more invasive surgery can often be avoided, minimizing complications, and lesions can be removed en-bloc.

The transbasal approach has historically been a work-horse for access to lesions in the anterior fossa, orbit, nasal cavity, paranasal sinuses, pterygopalatine fossa, and pituitary fossa. When combined with a transfacial route, increased visualization and access is provided to deeper structures with minimal brain retraction and decreased risk to neural and vascular structures. Due to the complexity of this approach, oftentimes requiring multiple surgical teams participating, the decision to utilize it should be made on a case-by-case basis after a multidisciplinary discussion. This chapter discusses the indications, anatomical, and surgical details required to treat benign and malignant neoplasms involving the anterior skull base, paranasal sinuses, and potentially the orbits.

Combined skull base approaches have become increasingly popular to address intracranial and head and neck lesions. Improved endoscopic visualization, endoscopic tools, and surgical techniques have allowed safer and more ready access to difficult regions in the skull base. Historically, the parapharyngeal space and infratemporal fossa have been considered distinct locations in the head and neck that have been a challenge to access. This chapter details endoscopic endonasal, transoral, and transcervical approaches, along with a review of general indications, utility, and microsurgical anatomy.

Statistical genetics and brain imaging are together at the technological forefront of research into human intelligence. While these approaches have historically had little practical overlap, they are united both conceptually and in several broad methodological challenges. In concept, both areas attempt to explain complex human behavior by understanding its biological origins, and in doing so have faced the problems that arise from this complexity. The prospect of finding large-effect predictors, for example, has shaped both histories: statistical genetics, with its study of candidate genes that were once thought to have outsized influence on the development of many traits, and neuroscience, with its search for localized brain properties underlying complex behaviors. Both of these areas have then had to adjust their scope and methodology to address the issue of making valid and meaningful predictions from a large number of predictors with small effects. A key understanding is that larger samples of participants than originally employed may be necessary for these predictions to be accurate and useful.