Predictive value of preoperative ventricular volume on the need for permanent hydrocephalus treatment immediately after resection of posterior fossa medulloblastomas in children.

OBJECT: In this study, the authors investigated whether preoperative ventricular volume can be used to predict the need for permanent treatment of hydrocephalus in children with posterior fossa medulloblastomas.

METHODS

Ventricular volumes were measured on magnetic resonance imaging studies obtained preoperatively and immediately postoperatively in 20 children who had undergone resection for medulloblastomas between 1999 and 2007. Comparison of mean values was performed using the one-way analysis of variance test. The association between ventricular and tumor volume was also investigated.

RESULTS

All patients had obstructive hydrocephalus preoperatively, and 4 patients required postoperative shunt placement. The mean preoperative ventricular volume was 252 ml for those who required shunt placement, and 106 ml for those who did not (p = 0.000). The postoperative ventricular volume was 157 and 78 ml, respectively (p = 0.039), larger than normal in both groups. The mean postoperative and preoperative ratios were 0.69 and 0.70, respectively (p = 0.932). There was no correlation of ventricular volumes with age at operation (older or younger than 3 years), presence of metastasis, or amount of residual tumor. There was a statistical correlation between the preoperative ventricular volume and the tumor volume, related to the need for permanent shunt placement.

CONCLUSIONS

Preoperative ventricular volume has predictive value for the later need for shunt placement, but in clinical practice this may be difficult to appreciate because all patients have significant hydrocephalus at presentation. The rate of ventricular size reduction in response to tumor excision does not have predictive value because ventricular volume is related to tumor volume. It appears that the removal of cerebellar medulloblastoma converts hydrocephalus from obstructive to communicating, which requires surgical treatment if it exceeds a certain level of cerebrospinal fluid volume.