by Michael McDowell, MD, and Daniel A. Wecht, MD
There has been extensive debate on the role of fixed pressure versus programmable pressure shunt valves in adult populations. A large succession of programmable valve types has surfaced to compete against older fixed pressure systems, which have gradually lost favor at many institutions. Programmability has been purported to provide the benefit of a reduced risk of shunt revision by allowing for dynamic intracranial pressure management, but these valves typically have a higher cost per unit.
Much of the published literature comparing the costs and clinical outcomes of programmable versus nonprogrammable shunts focuses on pediatric populations. Those studies examining fixed pressure shunts in adulthood are frequently dated or highly selective in terms of the underlying etiology requiring cerebrospinal fluid diversion. We investigated in detail the natural history of an adult patient population who universally received fixed valve shunt insertion as the initial treatment of hydrocephalus by a single physician. Between 2000 and 2017, 126 fixed pressure valves were inserted as the initial form of cerebrospinal fluid diversion in the senior author’s practice (Dr. Daniel Wecht) in patients without a history of prior cerebrospinal fluid diversion. All patients received a fixed pressure valve, with 94% being Pudenz medium pressure valves. The indication for shunting primarily included hemorrhagic hydrocephalus (43%), normal pressure hydrocephalus (38%), tumor-related hydrocephalus (6%), and pseudotumor cerebri (6%). Thirty-three (26%) required at least one revision, with a mean follow up time of 28 months. This corresponds closely to our department’s published programmable shunt revision rate as well as those published by other centers.
Nineteen patients (58%) required a single revision, 10 (30%) required two shunt revisions, and four (12%) required three or more revisions. The primary cause of shunt revision was mechanical shunt failure (39%) followed by infection (21%). Over-drainage was an indication for shunt revision in two patients (6% of revisions), and under-drainage likewise occurred in two patients (6% of revisions). Of note, all four patients requiring revision due to drainage-related issues had a diagnosis of normal pressure hydrocephalus. Shunt revision rate did not significantly vary by etiology. The difference in attributable hospitalization cost per shunt placement or revision when comparing patients within this cohort to those with programmable shunt placements performed by other surgeons at UPMC was an average of approximately $3,000 per operative case (p < 0.0001).
The primary criticism of fixed pressure shunts has focused on the inability to perform dynamic cerebrospinal fluid diversion management without a revision. Our findings suggest that the need to perform revision surgery due to under-drainage or over-drainage is very uncommon despite utilization of a standard medium fixed pressure shunt in almost all circumstances while treating a wide array of etiologies requiring cerebrospinal fluid diversion. The substantially greater cost for programmable shunts do not seem to come with a significant change in overall revision rate. We suggest, in an era of growing concerns regarding medical expenses, that non-programmable shunts should be considered as the primary initial form of cerebrospinal fluid diversion and that programmable valves may be beneficial only in circumstances where static cerebrospinal fluid management has been proven to be inadequate.