Fully endoscopic transvallecular transforaminal approach to the fourth ventricle epidermoids - cadaveric anatomy, surgical technique & case series.

Epidermoid cysts in the fourth ventricle are usually treated with either a microscopic or endoscope-assisted microscopic technique. The authors share their experience with four cases of fully endoscopic removal of fourth ventricular epidermoids using the transvallecular transforaminal approach, discussing the technical details and benefits. From June 2021 to July 2022, four patients with fourth ventricle epidermoid cysts underwent surgery at our center using a fully endoscopic transvallecular transforaminal approach (FETTA). Clinical details and surgical outcomes were analyzed retrospectively. Patients were followed for at least two years. A qualitative anatomical study of the endoscopic surgical anatomy and technique was conducted using five cadavers in the cadaveric laboratory. A fully endoscopic keyhole transvallecular transforaminal approach was found to be safe and effective for accessing and removing epidermoids from the fourth ventricle without needing a vermian split or telovelar incision. All patients achieved gross total tumor removal except one with a minimal residual lesion on postoperative imaging, and one patient experienced a CSF leak that was later repaired. All patients were asymptomatic at 2 years of follow-up. Fourth ventricle epidermoids, due to their avascular, soft, and suckable nature, are suitable for minimally invasive keyhole suboccipital craniotomy and endoscopic approaches, particularly when the tumor enlarges the foramen of Magendie and fourth ventricle. The vermian split or telovelar approach is unnecessary, as the tumor already provides enough space to work with endoscopic visualization. Two-surgeon dynamic endoscopy offers better access than static scope visualization, allowing access to crevices that are not visible with a microscope.