Lesions at the Foramen of Monro Causing Obstructive Hydrocephalus

The foramen of Monro has also been referred to by the name of interventricular foramen. The structures comprising this foramen are the anterior part of the thalamus, the fornix and the choroid plexus. Vital structures surround the foramen, the damage to which can be catastrophic leading to disability either temporary or permanent. In the literature it has been shown that tumors occurring in the area of interventricular foramen are rare and usually cause hydrocephalus. The operative approach depends upon the location of the tumor which can be either in the lateral or the third ventricle. Various pathologies which can lead to foramen of Monro obstruction and obstructive hydrocephalus include colloid cyst, craniopharyngioma, subependymal giant cell astrocytoma [SEGA], Neurocysticercosis, tuberculous meningitis, pituitary macroadenoma, neurocytoma, ventriculitis, multiseptate hydrocephalus, intraventricular hemorrhage, functionally isolated ventricles, choroid plexus tumors, subependymomas and idiopathic foramen of monro stenosis. In this chapter, we will discuss the various lesions at the level of foramen of Monro causing obstructive hydrocephalus and the management and associated complications of these lesions based on their type, clinical picture and their appearance on imaging