PURPOSE: To determine whether it is possible to select patients with obstructive hydrocephalus, in the under 1 age group for endoscopic third ventriculocisternostomy (ETV) using pre-operative T2 weighted turbo spin echo (T2W-TSE) sagittal sequence Magnetic Resonance (MR) imaging; and to assess ventriculocisternostomy patency using post-operative T2W-TSE MR.PATIENTS AND METHODS: A retrospective review of MR examinations and clinical notes of 11 patients under 1 year of age who had ETV, was performed. The post-operative flow MR images were divided into the presence or absence of flow-related signal changes.RESULTS: In 6 of the 11 patients, ETV was successful (54.5%) i.e. no VP shunt or revision of the ETV was required. 9 patients had post-operative T2W-TSE MR examinations — 8 of these 9 MR studies correlated to the clinical situation (89%). The remaining MR examination showed a CSF flow void but the ETV failed at 3 weeks.CONCLUSION: Pre-operative MR using T2W-TSE to select suitable candidates for ETV improves the success rate from < 40% to 54.5%. Post-operatively MRI is a good predictor of whether the ETV has been successful or not.Sharman, A. (2000). Clinical Radiology55, 989.