Over the past two decades, the endoscopic endonasal approach has significantly expanded the armamentarium of minimally invasive skull base surgery. Initially developed for the treatment of pituitary adenomas, endoscopic endonasal skull base surgery (EESBS) has found increasing utility in managing a broad spectrum of skull base pathologies. Its application extends from the midline, encompassing the crista galli process to the occipitocervical junction, and laterally to the parasellar areas and petroclival apex. In recent years, there has been a notable shift from the exclusive use of endoscopic technology in endonasal pituitary surgery to other neuroendoscopic procedures. This chapter aims to provide the reader with an up-to-date overview of clinical trials on endoscopic neurosurgery of the skull base, brain, and neuroaxis. Through a comprehensive review of the state-of-the-art published peer-reviewed literature, the authors strive to offer a concise summary of the current concepts in this rapidly advancing field.

Microendoscopic trigeminal nucleotractotomy (MENT) is a minimally invasive surgical procedure used to treat trigeminal neuralgia (TN). In this chapter, the authors describe the clinical outcomes associated with MENT regarding pain relief and functional improvement. Our novel technique resulted in a significant reduction in pain scores following MENT, as indicated by a decrease in the Visual Analog Scale (VAS) scores. Additionally, a substantial proportion of patients reported functional improvement, including enhanced ability to perform daily activities. The success of MENT is influenced by factors such as patient selection, surgical technique, and underlying causes of TN. Although the study provides short-term follow-up and feasibility data, further research with longer-term evaluations is necessary to assess the durability of pain relief achieved through MENT.

Endonasal endoscopic approaches have revolutionized surgical access to the sellar region and anterior fossa. These minimally invasive techniques utilize the natural nasal corridors to reach the target area, avoiding the need for external incisions. The endoscope provides excellent visualization and magnification, enabling precise surgical maneuvers. In this chapter, the authors describe the anatomical features for performing endoscopic endonasal approaches to the Sella and the anterior fossa. These approaches include the traditional endoscopic transsphenoidal approach to the Sella and extended endonasal approaches, including trans tuberculum, transplant, and transcribiform approaches. The most remarkable anatomical landmarks and surgical tenets are discussed. The anterior fossa houses critical structures like the anterior cranial base and the olfactory system. These structures can be approached for the resection of tumors, repair of cerebrospinal fluid leaks, and management of traumatic injuries. Endonasal endoscopic approaches offer reduced morbidity, shorter hospital stays, and faster recovery than traditional open approaches. Our clinical series shows that technological advancements and modern endoscopic surgical techniques further enhance the safety and efficacy of conventional transnasal methods, making them indispensable tools in the armamentarium of contemporary skull-base surgeons. 

Myelomeningocele (MMC) is the most relevant clinical variant of spina bifida - a birth defect resulting in an open vertebral column. The failure of the lumbosacral neural tube to close during embryonic development may compromise the spinal cord in utero due to exposure to amniotic fluid and irritation by the uterine wall. Resulting neurological deficits may vary depending on the spinal level involved. Most neural tube defects are diagnosed in the second trimester by ultrasound. Early prenatal diagnosis allows in-utero repair to diminish neurological deficits and the need for postnatal ventricular shunting. In this chapter, the authors present a brief review of the pathophysiology of fetal MMC and the various repair options, and their associated clinical outcomes. Clinical studies suggest improved short-term neurological outcomes with percutaneous minimally invasive and intrauterine fetoscopic techniques using endoscopes compared with an open prenatal or postnatal repair. The main limitations of these modern techniques are preterm premature rupture of membranes (PPROM) and dehiscence or leakage at the MMC repair. Additional benefits may include a lower risk of preterm labor, reduced need for postnatal revisions, and improved newborn maturity with higher gestational age. Fetoscopy may also offer better management of the membranes and primary closure of uterine port sites. The long-term cognitive, behavioral, and functional outcomes of fetoscopic MMC repair have yet to be determined. While cesarean section may be required for delivery in subsequent pregnancies after traditional open prenatal MMC repair to avoid uterine rupture, fetoscopic methods with externalization of the uterus by maternal laparotomy may allow spontaneous vaginal delivery at term.

Myelomeningocele (MMC) repair was traditionally performed postpartum. Developmental delay, neurological deficits, and the need for shunting are persistent problems associated with this type of repair. Alternative open prenatal repairs have been proposed. Clinical studies suggest improved short-term neurological outcomes with percutaneous minimally invasive and intrauterine fetoscopic techniques using endoscopes, when compared with an open prenatal or postnatal repair. In this chapter, the authors present the various currently practiced forms of percutaneous fetoscopic MMC repair. These are frequently carried out via externalization of the uterus through a maternal laparotomy. The primary limitations of these procedures are preterm premature rupture of membranes (PPROM) and dehiscence or leakage at the MMC repair. The authors also present their preferred three-layer repair technique and their clinical outcomes of a small case series performed to date. Their results suggest several benefits of the full percutaneous fetoscopic technique, including a lower risk of preterm labor, reduced need for postnatal revisions, and improved newborn maturity with higher gestational age. The authors conclude that fetoscopy may also offer better management of the membranes and primary closure of uterine port sites. The long-term cognitive, behavioral, and functional outcomes of fetoscopic MMC repair will need to be studied. Additional clinical outcome studies should show whether caesarean section may be required for delivery in subsequent pregnancies following the use of the fetoscopic technique to avoid uterine rupture that is commonplace after traditional open prenatal MMC repair. With the authors' technique, spontaneous vaginal delivery at term is feasible.

Spinal chordotomy is an alternative to analgesic opioid therapy, nerve blocks, and subcutaneous or intravenous techniques for cancer-induced pain. Patients with advanced metastatic disease require significant pain relief. Unfortunately, not all patients respond well to the standard therapies. For these patients, cordotomy offers a potential breakthrough. Cordotomy involves thermally disrupting the nociceptive pathways in the anterior spinothalamic tract to interrupt pain transmission from the spinal cord to the brain. The anterior spinothalamic tract is responsible for somatic pain sensations, touch, and temperature discrimination. This chapter presents an endoscopic-assisted percutaneous anterolateral radiofrequency intradural cordotomy technique. The entire procedure is done under direct endoscopic visualization of the cervical spinal cord. The authors provide an up-to-date summary of targeted minimally invasive pain intervention, which utilizes controlled electrical stimulation to confirm the physiological target. It is associated with less trauma to surrounding spinal tissue and lower risks due to vascular injury or adverse effects of intrathecal contrast.

Transcallosal hemispherotomy is a surgical procedure used to treat severe epileptic seizures from a single brain hemisphere. This procedure involves the disconnection of the affected hemisphere from the rest of the brain, effectively preventing the spread of epileptic activity and reducing the frequency and severity of seizures. Endoscopic anatomy plays a crucial role in transcallosal hemispherectomy, as it allows for a minimally invasive approach. Using endoscopic techniques, surgeons can access and visualize the corpus callosum, a thick bundle of nerve fibers connecting the two cerebral hemispheres. This technique provides a clear view of the anatomical landmarks and enables precise disconnection of the affected hemisphere, while preserving critical neural structures. In this chapter, the authors review the endoscopic anatomy relevant to the transcallosal hemispherectomy identification of the corpus callosum's rostrum, genu, body, and splenium. By carefully navigating through these structures, surgeons can safely sever the connections between the affected and healthy hemispheres. This disconnection allows for better seizure control and improved quality of life for patients with severe epilepsy. The use of an endoscopic technique for transcallosal hemispherectomy may enable neurosurgeons to employ a minimally invasive approach to accomplish a precise disconnection of the affected hemisphere. It may thus form the basis for improved patient outcomes.

Initial treatments for craniosynostosis involved strip craniectomies, but due to unsatisfactory results in advanced stages, extensive cranial remodeling was introduced, despite its risks and prolonged hospital stays. Over the last 30 years, strip craniectomies have seen a revival, primarily due to the incorporation of minimally invasive endoscopic-assisted surgeries (EAS) as pioneered by Jiménez and Barone. EAS has shown marked advantages over older surgical methods, including shorter surgical times, reduced bleeding, and fewer hospitalization requirements, all while achieving comparable results in cranial deformity corrections. The most influential factor in perioperative morbidity is surgical time. EAS has emerged as a promising, effective treatment for craniosynostosis, suggesting its wider adoption in neurosurgical settings. Considering the relationship between age, surgical time, and blood loss, EAS may be suitably extended to children aged 6-12 months.

Trivialization of durotomy can cause complications for endoscopic spine surgeons when a patient's neurological or cardiovascular status unexpectedly deteriorates during or after surgery. The literature on fluid management strategies, irrigation-related risk factors, and clinical consequences of incidental durotomy during spinal endoscopy is limited. However, it suggests that most patients can be managed with supportive care without formal dural repair. There is currently no validated irrigation protocol for endoscopic spine surgery. In this chapter, the authors report severe complications in several patients, including the spread of irrigation fluid, blood, and air into the intradural and intracranial spaces. They concluded that patients should be informed about the risks associated with irrigated spinal endoscopy before surgery. Infrequent yet not insignificant, adversities encompassing intracranial hemorrhage, hydrocephalus, cephalalgia, cervical discomfort, convulsive events, and the perilous autonomic dysreflexia manifesting as hypertensive episodes can transpire should the irrigation fluid inadvertently enter the spinal cord or dural sac. Adept endoscopic spinal surgeons postulate an association between durotomy events and equilibration pressures associated with irrigation, a conjunction that, when amalgamated with copious irrigation volumes, may prove disconcerting. Further research is needed to determine whether specific thresholds for pressure, flow, and total volume of irrigation fluid should be established and to identify any additional risk factors beyond incidental durotomy or prolonged surgery time.

Thoracic endoscopic spine surgery is gaining traction. During thoracic decompression, the arterial Adamkewicz system (AKA) can be encountered, with potentially severe implications if injured. This chapter outlines a diagnostic protocol and patient selection for the surgery based on a study examining surgical risks tied to the radicular magna artery. The authors share insights from fifteen patients with thoracic herniated discs and spinal stenosis who underwent preoperative CTA. This assessed the anatomical relationship of the Magna radicular artery to the surgical area. The Adamkiewicz artery's prevalent locations were T10/11 (15.4%), T11/12 (23.1%), and T9/10 (30.8%). Patients were grouped into three categories based on their pathology's proximity to the AKA foraminal entry. In five instances, the Magna radicular artery entered the spinal canal near the nerve root at the surgery site, prompting a surgical approach adjustment. The authors advocate for CTA evaluation to gauge surgical risks and adapt thoracic discectomy techniques based on the magna radicular artery's closeness to the pathology.