Endoscopic third ventriculostomy and posterior fossa tumors.

BACKGROUND

The management of hydrocephalus associated with a posterior fossa tumor is debated. Some authors emphasize the advantages of an immediate tumor removal that may normalize the cerebrospinal fluid (CSF) dynamics. However, in clinical practice, the mere excision of the lesion has been demonstrated to be accompanied by a persisting hydrocephalus in about one third of the cases. Preoperative endoscopic third ventriculostomy (ETV) offers several advantages. It may control the intracranial pressure (ICP), avoid the necessity of an emergency procedure, allow appropriate scheduling of the operation for tumor removal, and eliminate the risks related to the presence of an external drainage. The procedure also reduces the incidence of postoperative hydrocephalus. A final advantage, more difficult to weight, but obvious to the neurosurgeon, is the possibility to remove the lesion with a relaxed brain and normal ICP. In the postoperative phase, ETV can be used in case of persisting hydrocephalus, both in patients who underwent only the excision of the tumor and in those whose preoperative ETV failed as a consequence of intraventricular bleeding with secondary closure of the stoma (redoETV). The main advantage of postoperative ETV is that the procedure is carried out only in case of persisting hydrocephalus; its use is consequently more selective than preoperative ETV. The disadvantage consists in the common use of an external CSF drainage in the first few postoperative days, which is necessary to control the pressure and for ruling out those cases that reach a spontaneous cure of the hydrocephalus.

METHODS

The authors review the criteria for patient selection and the results of ETV performed in case of hydrocephalus secondary to a posterior fossa tumor.

RESULTS AND CONCLUSIONS

Preoperative ETV constitutes an effective procedure for controlling the hydrocephalus associated with posterior fossa tumors. It might lower the rate of persistent postoperative hydrocephalus and result in a short hospital stay. Low rates of patients requiring an extrathecal-CSF shunt device are also reported by authors who utilize ETV postoperatively. As, however, the assessment of the persistent hydrocephalus in these children is based on prolonged ICP monitoring through an external CSF drainage, their results are weighted by a major risk of infective complications and longer hospital stay.