Obstruction of third ventriculostomy: Diagnosis and management

Endoscopic third ventriculostomy has become the preferred treatment for obstructive hydrocephalus. However, despite the creation of an alternative CSF pathway, ETV failure may occur. ETV failure has three reasons: misinterpreting the primary condition as an obstructive, failure to absorb the CSF at the convexity subarachnoid space and arachnoid granulations, and closure of the stoma. Stoma closure is considered the main reason for late failures. In most cases, a closed stoma by scar tissue is found. To date, there are no known risk factors for late ETV closure, but late failures do occur even years following the procedure. Thus, all patients following an ETV, regardless to the primary reason of their hydrocephalus, are routinely followed with yearly clinical and ophthalmological evaluations. Patients and their families are alerted about relevant symptoms that may arise and suggest ETV failure. Additionally, we recommend routine surveillance MRI scans to screen for ETV closure. The parameters which we consider as important in evaluating ETV success include: 1. Ventricular size 2. Periventricular edema 3. Ballooning of the third ventricle 4. Flow void through the ETV stoma 5. Convexity subarachnoid space In this chapter, we review the pitfalls in diagnosing ETV closure, alternative imaging sequences which highlight the flow void through the ETV, timing of surgical treatment, and various treatment options at failure.