Introduction: Tumours arising in posterior fossa are of special concern because it is a small and closed space near critical brain structures including the brainstem and cranial nerves. The percentage of pre operative shunting in hydrocephalic posterior fossa tumours has been quite variable in different studies. The aim of this study is to check the factors that will help in prediction and thus isolate the patient group which wil require postoperative VP shunting. Materials and Methods: One hundred children of posterior fossa tumour were included in the study and out of these sixty were associated with hydrocephalus external ventricular drain (Surgiwear shunt and drain systems) was put just prior to surgery in all patients with established clinical and radiological signs of raised intracranial pressure. CSF was drained as required and the EVD was removed on fifth postoperative day. Postexternal ventricular drain removal, patients were reassessed in terms of clinical and radiological signs of raised intra cranial pressure and a VP shunt (Surgiwear’s Chabbra slit n spring system shunt) was put in the presence of the same. Various parameters like age, sex, type and location of tumour, type of surgery and extent of resection were recorded, data was compiled and results were tabulated. Results: Out of total of 18 children who required postoperative VP shunting, age less than 3 years, midline location of tumours and residual lesion were found to be the properties in the shunted group which showed statistically significant results. On the other hand, type of tumour(intra/extra axial) and sex of the patient proved to be insignificant for predicting the need of a postoperative VP shuting in patients of posterior fossa tumour. Discussion: Treatment of hydrocephalus in posterior cranial fossa tumours is still a matter of controversy and the incidence of this association is stil quite unclear and the factors determining the need of VP shunt in this study, i.e. age <3 years, midline location of tumour and subtotal resection are also validated by other authors. Conclusion: Children with posterior fossa tumours with hydrocephalus are particularly at risk of a permanent VP shunt if age of the patient is < 3years, tumour is located in midline and residual tumour postoperatively.

Keywords: Hydrocephalus; Posterior fossa tumour; CSF Diversion Surgery.