cardiorespiratory maintenance, emergent cranial imaging and assessment by a neurosurgeon are essential Definitive treatment will require some form of surgery In some cases, there may be discreet tumor mass causing obstructive hydrocephalus and the goal of surgery will be tumor resection, which may relieve the hydrocephalus In other situations, treatment will require diversion of the CSF itself, in the form of either a CSF shunt or an endoscopic third ventriculostomy (ETV) FIGURE 122.4 An approximately 4.7 × 3.3 × 3.5 cm T1 hypointense, minimally heterogeneous, circumscribed mass fills the fourth ventricle, which is effaced toward the right, and displaces the pons and medulla anteriorly There is resultant mild– moderate dilatation of the lateral ventricles, third ventricle, and cerebral aqueduct