**Abstract**

Management of pediatric skull base tumors requires a multi-disciplinary team that integrates advances in neuro-imaging, radiation, medical and surgical treatments, and allied therapies. Tumors of the skull base harbor complex genetic and molecular signatures that have major implications on prognosis and quality of life. Individualized management requires a strong inter-disciplinary alliance amongst practitioners, as well as a strong therapeutic alliance with the patient and family to navigate the complex decision-making process of treatments. In this chapter, we present our experience managing surgical lesions of the pediatric skull base. General considerations to tumor pathology genetics and radiobiology, diagnostic imaging, rehabilitation of cranial neuropathies and cognitive function, surgical anatomy and reconstructive options, and quality of life should be applied to each case. We also present location- and tumor-specific considerations in the anterior, middle, and posterior fossa skull base with a focus on surgical approaches and complication avoidance. Special consideration is given to syndromic tumors, particularly those from neurofibromatosis type 2 (NF-2). Tumors can exist in multiple cranial compartments and as such some redundancy in concepts is unavoidable. Nevertheless, each patient presents with a unique clinical picture and tumor behavior. Knowledge and proficiency in skull base approaches is a necessary tool in every pediatric neurosurgeon's armamentarium.

**Keywords:** pediatric brain tumors, skull base tumors, pediatric neuro-oncology, pediatric neurosurgery

## **1. Introduction**

Contemporary management options for skull base tumors include observation, stereotactic radiosurgery or radiotherapy, primary or adjuvant chemotherapy, and microsurgical resection. Factors influencing treatment decisions include patient age and medical condition, cranial neuropathies, tumor size, tumor genetics, and provider bias. Advances in imaging and treatment technologies have led to improved detection of small skull base tumors, a better understanding of the natural history of tumor growth, and reductions in post-operative morbidity and mortality.

We strongly advocate for a team-based approach to treat skull base tumors. Our program is led by a neuro-oncology and neurosurgery team, and composed of neurophysiologists, head and neck surgeons, radiation oncologists, ophthalmologists, plastic and reconstructive surgeons, as well as occupational- physical- and speech- therapists. Microsurgical resection is carried out in cases not amenable to observation or radiation therapy. Where applicable, and when neurologic function is not deteriorating, biopsy and individualized medical treatment is pursued in favor of radical resection. For example, advances in epigenetics and tumor expression profiles sensitive to *BRAF-V600E* confer favorable treatment response to kinase inhibitors in papillary craniopharyngioma [1]. In such cases, resection as index treatment is carried out in cases of neurologic deterioration, failed medical therapy, or favorable tumor handling at the time of biopsy.

Cranial nerve function takes priority when deciding to proceed with surgery. This is true both for extra-medullary lesions and intra-medullary lesions with exophytic components threatening cranial nerve function. The goals of resection should be considered when tailoring the surgical approach. For lower grade tumors, which comprise the majority of lesions, gross total resection with preservation of cranial nerve function is the standard of care. When cranial nerve function is threatened by poor tumor handling or adherence to adjacent neural or vascular structures, subtotal resection should be considered. This is especially relevant to lower cranial nerve function, which protects the airway and is associated with mortality when injured. Vision, oculomotor function, facial, and vestibulocochlear nerve function should also be considered.

Tumors that affect multiple cranial nerves together deserve special attention. This includes tumors that could affect all three oculomotor nerves, the fifth and seventh nerve together leading to insensate corneal abrasions and vision loss, and the lower cranial nerves together resulting in airway failure and death. Patients with contralateral cranial nerve dysfunction, such as in neurofibromatosis type 2 (NF-2), should also be given special consideration. In the case of bilateral acoustic neuromas, when contralateral hearing is absent, every attempt should be made to preserve ipsilateral hearing before attempting surgical resection. Bevacizumab has shown variable effect on tumor size and hearing function in such cases.
