The indications for neuroendoscopic operations have been standardized in the last few years. In general, neuroendoscopy is used for procedures in preexisting or pathologically formed cavities in the central nervous system.

Hydrocephalus
In the treatment of hydrocephalus, neuroendoscopic techniques can be used to reconstitute or recreate the natural pathways of cerebrospinal fluid (CSF) flow, and thereby to obviate the need for the insertion of a shunt system (foreign body in the brain). Endoscopic third ventriculostomy (ETV) has come to new life as a concept for the treatment of occlusive hydrocephalus because of the complications commonly associated with the implantation
of shunts to treat hydrocephalus, including shunt malfunction, thrombosis, infection, overdrainage, and slit-ventricle syndrome. In occlusive hydrocephalus, the CSF resorption mechanisms remain intact, and “internal shunt methods” such as ventriculostomy can,
therefore, be used.

patients whose hydrocephalus has been treated with shunts and who have suffered multiple episodes of shunt malfunction can be successfully treated with neuroendoscopy, so that they can do without a shunt from then onward. Patients considered to be at elevated risk of complications from surgical shunt revision,including those with post-hemorrhagic and post-meningitic hydrocephalus¬† should have an endoscopic procedure instead. Since the advent of endoscopy, the old clinical rule “once a shunt, always a shunt” thankfully no longer applies.

Intracranial cysts
Intracranial cysts are particularly suitable for neuroendoscopic treatment. Colloid, arachnoid, and pineal cysts can be endoscopically aspirated and fenestrated or removed. For the
treatment of cystic craniopharyngiomas, dysontogenetic tumors, gliomas, and metastases, neuroendoscopy can be used in combination with microsurgical resection, radiotherapy, and adjuvant chemotherapy.

Colloid cysts
Colloid cysts, because of their intraventricular location, are a classic indication for neuroendoscopy. Patients with symptoms of occlusive hydrocephalus are treated operatively. For asymptomatic patients, an operation is indicated when the cyst is large enough to threaten an acute occlusion of the foramen of Monro, which would cause acute occlusive hydrocephalus. A preventive operation is justified in view of the reports of sudden death in previously asymptomatic patients with colloid cysts.The postoperative results of neuroendoscopic surgery for colloid cysts are at least as good as those of microsurgery in terms of morbidity, mortality, and recurrence rates.

Arachnoid cysts
Intra-arachnoidally located cysts filled with CSF are called arachnoid cysts. They can be found intracranially at many different sites. Most of these cysts are large cavities in the immediate vicinity of the ventricular system or the intracranial cisterns and are therefore
well suited to a neuroendoscopic approach. This is particularly true of so-called suprasellar arachnoid cysts. An operation is indicated when the arachnoid cyst is symptomatic, i.e., when it elevates the intracranial pressure, causing headache or other neurological symptoms and signs. Neuroendoscopy can be used alone or in combination with conventional microsurgery.

Solid intraventricular tumors
Solid intraventricular tumors, too, can be treated with neuroendoscopy. Such tumors are preferably biopsied with neuroendoscopic guidance, rather than “blindly” by stereotaxy. Biopsy under direct vision is particularly advantageous in the area of the foramen of Monro, as well as for pineal tumors in the posterior portion of the third ventricle. The operative approach can be chosen to spare ventricular vessels and functionally important structures,
because endoscopy, unlike stereotaxy, offers the neurosurgeon a direct visual check. If the tumor is causing occlusive hydrocephalus (e.g., because of its location in the posterior portion of the third ventricle), a third ventriculostomy can be performed at the same sitting, or, alternatively, a stent can be inserted between a lateral ventricle and the third ventricle, or between the third and fourth ventricles.The likelihood of complete tumor resection via neuroendoscopic surgery is a function of tumor size.