Editorial: Acoustics and hydrocephalus

Abstract

This retrospective study regarding management options in patients with hydrocephalus associated with vestibular schwannomas (VSs) comes from a center with a remarkably large surgical experience treating this tumor type.1 Their surgical technique has been exquisitely developed over many years, and is uniform among colleagues in their institution. They receive worldwide referrals and treat a greater than usual number of larger VSs. This helps to account for their significant experience with hydrocephalus in patients with this specific tumor; that is, larger tumors often present for a longer than usual period of time. Their consecutive series of 400 patients was collected over a 6-year period (an average of more than 66 cases per year). Their overall results with complete tumor removal and percentage of saved facial nerve function and preserved hearing is among the best reported in the medical literature. 3In evaluating the superb results herein reported ("The general and functional outcome of surgery showed no correlation to the presence of preoperative hydrocephalus."), the above statements and the fact that these patients undergo operation in the semisitting position, with very experienced neuroanesthesiologists performing the anesthesia, must be taken into account. In most centers around the world, patients undergo this surgery in a supine (flat or slight reverse Trendelenberg) position, with the head turned or in a lateral position.2 Patients with hydrocephalus, even those with modestly elevated intracranial pressure (ICP), at induction of anesthesia can have their ICP severely elevated, and this may be obviated in the sitting position. Modest or marked elevation of the ICP will often make it more difficult to perform the surgical procedure safely and to accomplish the removal of the entire tumor while sparing the critical cranial nerves.My own recommendation (and I believe the procedures that are followed in most centers where patients are not operated on in the sitting position) would be as follows: 1) patients with symptomatic hydrocephalus accompanied by elevated ICP would have an external ventricular drain (EVD) placed, and when the ICP normalized in 1 or 2 days, they would be taken to surgery. The EVD would be left in place postoperatively, and then the patient would be gradually weaned from the drain. If weaning was not possible (as the authors recommend), a ventriculoperitoneal shunt would be placed. 2) Patients with asymptomatic hydrocephalus and those with normalpressure hydrocephalus (NPH) symptomatology would have an EVD placed at the beginning of anesthesia, the pressure would be kept in a normal range during the operation to mitigate elevated pressure transmission to the posterior fossa, and then after surgery the drain would be left in, and then usually removed in 1-2 days, as long as the clamped pressure permitted this. With this approach, the incidence of permanent hydrocephalus (obstructive or communicating), and CSF leakage would probably be similar to that reported herein. The authors empha...

Communicating Hydrocephalus and Vestibular Schwannomas: Etiology, Treatment, and Long-Term Follow-Up

“…However, the current consensus of opinion seems to favor the preoperative placement of an EVD in patients with a VS if either communicating or noncommunicating hydrocephalus is present. 24…”

Hydrocephalus Associated with Large Vestibular Schwannoma: Management Options and Factors Predicting Requirement of Cerebrospinal Fluid Diversion after Primary Surgery

“…There is a common acceptance that large tumors with obstructive HCP can cause operative morbidity due to cerebellar bulge, venous bleeding, difficulty achieving hemostasis, and need of retraction. It has also been previously stressed that sitting position may have less of these operative difficulties,[ 17 ] and a perioperative external ventricular drain may increase safety in cases with raised ICP. The recommended crucial action that allows the surgeon to control the ICP is to open the cerebellomedullary cistern early and drain sufficient CSF.…”

“…Craniotomy can be extended down and laterally and dural incised basally, to elevate the cerebellum and access the cisterns. [ 17 ]…”

Hydrocephalies and Vestibular Schwannoma of Great Size: Therapeutic Strategies: About a Series of 32 Cases

“…In the event that schwannoma resection surgery is prioritized in a intracranial hypertension patient by hydrocephalus, the risk of intraoperative cerebellar involvement at the opening of the dura mater would expose to an easily understandable surgical risk [3] [12]. Some authors favor the implantation of a EVD in these cases before the excision of SV [18]. The delay between the placement of this EVD and the lesion excision surgery must be reasonable in order to minimize the infectious risks associated with the presence of the drain.…”