Changing Treatments: Converting from a Shunt to an ETV for the Treatment of Hydrocephalus

A recent study published in Neurosurgery looked at the success rate of converting from a shunt to an endoscopic third ventriculostomy (ETV) in pediatric and young adult patients. The study, with lead author Dr. David S. Hersh, retrospectively reviewed patient data from three children’s hospitals in the United States. The study included 80 patients representing a number of different types, or etiologies, of hydrocephalus. The most common etiology was aqueductal stenosis (19 of the 80 patients).

For the analysis, the patients were placed into one of three groups:

1. Posthemorrhagic hydrocephalus (with or without prematurity),
2. Aqueductal stenosis and/or tumor causing obstruction to cerebrospinal fluid (CSF) flow, or
3. Other, including but not limited to spina bifida-related, Dandy-Walker-related, and postinfectious etiologies.

The ETV conversion was considered to be successful if the patient was shunt independent by the time of the last follow-up visit. 63.8% of the patients had a successful ETV conversion. Most of these were successful after one surgery, however 7.8% of the successes required a redo ETV to achieve shunt independence. The 63.8% success rate presented in this study is similar to the success rates found in other studies.

The study also looked at a variety of variables such as age, gender, etiology of hydrocephalus, and suspected site of obstruction (aqueduct, third ventricle, fourth ventricle, or unknown) in order to determine if there were any predictors of ETV success. The only statistically significant predictor of success was age; older patients had higher rates of success than younger ones.

While obstruction site was not found to be a statistically significant predictor of success, the authors hypothesize this was likely due to an overrepresentation of certain obstruction sites within their patient population. However, they theorize that site of obstruction likely would be a more important variable for success than etiology of hydrocephalus. In fact, based on research done by other groups, the authors caution against dismissing certain etiologies of hydrocephalus, such as posthemorrhagic and postinfectious hydrocephalus, as candidates for ETV conversion. Inflammation and scarring from the original cause of hydrocephalus may lead to new obstructions at narrow points on the CSF pathway, such as in the aqueduct of Sylvius, which would make the patient a good candidate for ETV even if they were not at the onset of their hydrocephalus.

The authors recommend that surgeons consider ETV conversion for patients presenting with shunt malfunction, taking care to identify and consider the point of obstruction in addition to the hydrocephalus etiology, when making their determination.

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