In “Neuroendoscopic third ventriculostomy for failed shunts” (Surg Neurol 2003), Buxton and co-workers present their clinical experience using neuroendoscopic third ventriculostomy (ETV) in patients with failed hydrocephalus shunts. This paper reviewed the outcome in shunted patients with hydrocephalus whose initial implanted shunt failed and who were subsequently treated with ETV. Subsequent failure of the ETV occurs when the symptoms of hydrocephalus return so that further treatment for the hydrocephalus is required. A total of 88 patients were identified; 45 (51%) were male and 43 (49%) were female. Median age at time of the ETV was 14 years (ranging from 1 day to 69 years). Median time from last shunt to the ETV surgery was eight years (ranging from 1 week to 35 years). Follow-up after the ETV surgery was for a median of three years (ranging from one month to six years).
ETV is an alternative procedure to shunt implantation. An opening or hole is made in the floor of the third ventricle of the brain using a miniaturized telescope that is introduced into this fluid-filled cavity of the brain through a cannula or tube. The hole allows the cerebrospinal fluid (CSF) to flow out of the third ventricle via a natural bypass to the subarachnoid space. Care must be taken to avoid damage to the Basilar Artery, the blood supply to the brainstem (a structure that controls important bodily functions). The primary complications are fever and bleeding. If successful, the procedure avoids a foreign body (the shunt) and the increased risk of infection associated with implanted devices in the brain. Overdrainage complications associated with shunts are avoided. One of the major problems of this procedure is that the hole could close. When this occurs, the symptoms of hydrocephalus return.
The clinical results of this study demonstrated that, overall, 42 (48%) of the procedures failed and 46 (52%) were successful. In patients with noncommunicating causes, the success rate was 73%. Median time to failure was one month (ranging from immediate to five years). Median age of failed patients at time of ETV was seven years. Serious complications occurred in five (5.6%) patients.
The authors conclude that ETV in previously shunted patients is safe and as successful as in patients in whom ETV is performed as the initial surgery to manage hydrocephalus. Failure can be expected to occur with greater frequency in communicating (all CSF passageways are open to the arachnoid villi—the natural structures that drain CSF into the bloodstream) than in noncommunicating types of hydrocephalus where there is a blockage somewhere in the ventricular system. The fact that the patients have a malfunctioning shunt in place is not a contraindication to this procedure. In cases of infected shunts, ETV is a useful adjunct to the treatment of the infection. It allows the infected shunt hardware to be removed while offering a method to manage the patient’s hydrocephalus.
A commentary at the end of the article, by Dr. A. Leland Albright, Chief of Neurosurgery, Children’s Hospital of Pittsburgh, notes that the authors’ suggestion that shunt malfunction, in the presence of shunt infection, can be treated using ETV rather than shunt revision is an important conclusion. He added two cautions:
• ETV is usually not effective in patients with posthemorrhagic hydrocephalus as evidenced by the 1/11 success rate experienced by the authors.
• The effectiveness of ETV in postmeningitic hydrocephalus, 2/6 success in the authors’ experience, cannot be determined on the basis of six patients.
With reference to the conclusion that patients with posthemorrhagic hydrocephalus will not benefit from ETV, a more optimistic outlook has been presented in other studies. Siomin and co-workers (J Neurosurg 2002) evaluated the safety, efficacy and indications for ETV in patients with a history of subarachnoid (SAH) or intraventricular hemorrhage (IVH) with or without CSF infection. They performed a retrospective analysis of 101 patient records from seven hospitals; 46 patients had a history of hemorrhage (SAH or IVH), 42 had a history of CSF infection, and 13 had both bleeding and a CSF infection. Third ventricular hydrocephalus was present in all patients before endoscopy was performed. The success rate for ETV treatment (with a follow-up period ranging from 0.6 to 10 years) was 60.9% after hemorrhage alone, 64.3 after infection alone, and 23.1% after both bleeding and CSF infection. Relatively minor complications were observed in 15 patients (14.9%). There were no deaths. A higher rate of treatment failure was associated with:
• classification in the combined infection/hemorrhage group,
• premature birth in the posthemorrhage group, and
• younger age in the postinfection group.
A higher success rate was associated with a history of VP shunt placement before ETV in the posthemorrhage group, even among those born prematurely (who are otherwise more prone to treatment failure). The 13 premature infants who had an IVH and who had undergone VP shunt placement prior to ETV had a 100% success rate. The procedure was also successful in 9 of 10 patients with primary aqueductal stenosis. The authors conclude that patients with obstructive hydrocephalus and a history of either hemorrhage or infection may be good candidates for ETV. Patients who have sustained both hemorrhage and infection are poor ETV candidates, except in selected cases and as a treatment of last resort. “In patients who have previously undergone shunt placement posthemorrhage, ETV is highly successful. It is also highly successful in patients with primary aqueductal stenosis, even in those with a history of hemorrhage or CSF infection.”
Baskin et al. (J Neurosurg 1998) assessed a protocol to evaluate and treat patients with slit ventricle syndrome (SVS). All patients underwent fiberoptic intracranial pressure monitoring after removal or externalization of their ventricular shunt systems. A significant number of patients tolerated shunt system removal without requiring further intervention. Patients demonstrating a continued need for CSF drainage underwent an ETV regardless of the supposed cause of hydrocephalus. Sixteen of 22 patients (72.7%) experienced a significant improvement of their SVS complaints and 14 of 22 patients (64%) were no longer shunt dependent after a mean follow-up period of 21.4 months. The authors note that “(t)he success of ETV in two patients who were shunt dependent as a consequence of previous IVHs illustrates the limitations of systematically excluding patients for this procedure based on the outdated and arbitrary designations of their hydrocephalus as ‘obstructive’ or ‘communicating’. By definition, all patients with hydrocephalus have an obstruction to CSF absorption at some point along their CSF circulatory pathway and the more accurate description...of hydrocephalus as either intra- or extraventricular remain most meaningful. One would expect ETV to be successful whenever the procedure bypasses the obstruction, whether it exists within the ventricular system or at the level of the basal cisterns. Furthermore, if symptomatic hydrocephalus is related to a series of partial circulatory obstructions, circumventing some of these points by ETV might be sufficient to enable patients to compensate for their remaining disease and to avoid dependence on a shunt system.”
It is clear that this question needs more statistical analysis before any firm conclusions can be made. It is important to note that there are risks of more serious complications in ETV than with shunt implantation including ocular nerve palsies, stroke and bleeding from the Basilar Artery. Because there is a considerable difference in technical difficulty between shunt implantation and ETV, appropriate training for performing the ETV procedure is important.
ETV is an alternative to shunting that may allow patients with hydrocephalus to avoid shunt implantation or allow a patient with a nonfunctioning shunt to have it removed. It is important for patients to understand the risks and benefits of this procedure. For additional information, see the newsletter article on ETV.
Why re-invent the wheel? There was nothing wrong with the old ones. This may be true for wheels but not when it comes to the treatment of hydrocephalus. It wasn't until the 1960s, with the development of implants. that the treatment of hydrocephalus became possible and shunts (the diversion of fluid from brain to chest, the heart, or usually the belly with silicone tubing) became a routine procedure for neurosurgeons and others. Apart from technical advances in structure and shape, the concept has remained the same. The problems associated with shunts haven't changed either. Shunts still fail mechanically, block, overdrain and infect. Very little can be done on this front and if shunts were kitchen appliances, the manufacturers would recall them.
There is an alternative which is endoscopic third ventriculostomy. This very old procedure (dating back to the 1900s) was abandoned because of outrageous complications due to poor anaesthetics and inappropriate equipment. Technical progress in optics, electronics and image processing have made endoscopy (which means looking inside something) accessible to all medical disciplines. In the 1980s endoscopic instruments were purpose-built for neurosurgery and an increasing number of applications were found. Currently in our department two or three neuroendoscopies are performed per week for a variety of indications, mostly for the treatment of hydrocephalus but also in tumour surgery.
Endoscopic ventriculostomy, which means opening the floor of the brain using a miniaturised telescope, was one of the first applications. Because of the position of the cavities of the brain, specifically in hydrocephalus, you can navigate from the top of the skull through the brain to the floor of the brain. The floor is very thin and can be opened using a laser fibre or another cutting device. This allows the fluid to flow out of the brain via a natural bypass. The risk of this procedure is very low and there are very few potential side effects, there is no overdrainage, no blockage, the risk of infection is very small and, most important of all, there is no foreign material left behind that can cause difficulties at a later date. The success of this treatment is determined by what caused the hydrocephalus in the first place. If the natural outflow of fluid is blocked by a tumour or from birth (obstructive hydrocephalus) the success rate is 85%, when there has been an infection (meningitis) or a bleed in the brain the success rate is about 50%. The overall success rate for endoscopic ventriculostomy in hydrocephalus is two-thirds. The advantage is that once a ventriculostomy functions and the hydrocephalus is relieved there is no need for further surgery. Ventriculostomy, when successful, is a one-off procedure with permanent result. We now treat an increasing number of patients with shunt complications with the same overall success rate. Having a shunt in place does not preclude endoscopic treatment.
This compares favourably with the 'classic' treatment of hydrocephalus, ie shunts, since 70% will fail within a 10-year period and a child needs a mean of five to six shunts before reaching adult age. We have come to the point that we offer endoscopic treatment for every new case of hydrocephalus and for every shunt blockage.
But what if the endoscopic treatment does not work? Overall there remains one-third of the patients in whom the procedure will not relieve the hydrocephalus. In those patients the only option is to divert the fluid with a shunt. A prior ventriculostomy does not influence the procedure. Up to now there is no way of predicting which patient will benefit from the procedure so we must remain honest about the results and it is only after a lengthy and informative talk with the parents that we proceed. Unfortunately, we can't take any credit for either the operation or the equipment, but we may have re-invented the wheel in the sense that we are rediscovering an old procedure using the latest technology and improving the results.