Pathology of Hydrocephalus due to Posterior Fossa Tumors in Children
Resolution of hydrocephalus after tumor removal
Variance in ability to handle ventriculomegaly: A recent study found that children with enlarged ventricles experienced a 30% reduction in ventricular volume on average after resection of their medulloblastomas regardless of whether or not they were shunted. For both groups the mean postoperative ventricular volumes were abnormally high, confirming that postoperatively these patients had a state of communicating hydrocephalus. However, in the patients for whom shunting was not required, the brain was able to handle that state of communicating hydrocephalus unaided until its resolution; whereas in those who required shunting the ventricular volume was too high to be handled without external diversion (22).
Evolution in extraaxial CSF circulation: Nishiyama et al. showed that CSF dynamics convert from a shunt-dependent state to a shunt-independent state within 1 week of ETV in patients with shunt-dependent non-communicating hydrocephalus (29). Nonetheless, intraventricular pressure does not decrease quickly in certain cases, and CSF absorptive capacity or CSF circulation through the subarachnoid space may show further improvement several months after ETV (28).