Abstract
Diagnosis of symptomatic valve malfunction in hydrocephalic patients treated with VP-Shunt (VPS) might be difficult. Clinical symptoms such as headache or nausea are nonspecific, hence cerebrospinal fluid (CSF) over- or underdrainage can only be suspected but not proven. Knowledge concerning valve malfunction is still limited. We aim to provide data on the flow characteristics of explanted shunt valves in patients with suspected valve malfunction. An in vitro shunt laboratory setup was used to analyze the explanted valves under conditions similar to those in an implanted VPS. The differential pressure (DP) of the valve was adjusted stepwise to 20, 10, 6, and 4 cmH2O. The flow rate of the explanted and the regular flow rate of an identical reference valve were evaluated at the respective DPs. Twelve valves of different types (Codman CertasPlus valve n = 3, Miethke Shuntassistant valve n = 4, Codman Hakim programmable valve n = 3, DP component of Miethke proGAV 2.0 valve n = 2) from eight hydrocephalic patients (four male), in whom valve malfunction was assumed between 2016 and 2017, were replaced with a new valve. Four patients suffered from idiopathic normal pressure (iNPH), three patients from malresorptive and one patient from obstructive hydrocephalus. Post-hoc analysis revealed a significant difference (p < 0.001) of the flow rate between each explanted valve and their corresponding reference valve, at each DP. In all patients, significant alterations of flow rates were demonstrated, verifying a valve malfunction, which could not be objectified by the diagnostic tools used in the clinical routine. In cases with obscure clinical VPS insufficiency, valve deficiency should be considered.
Highlights
Implantation of a ventriculo-peritoneal shunt (VPS) is the most widely used neurosurgical procedure to treat patients with hydrocephalus
Up to 25% of patients suffering from idiopathic normal pressure hydrocephalus develop primary deterioration after VPS
In case of suspected underdrainage, low-dose CT-shunt-series as well as conventional contrast-enhanced shunt series failed to demonstrate radiological evidence of shunt failure [13, 35, 36], while clinical symptoms were persistent despite multiple adjustments of the respective valve
Summary
Implantation of a ventriculo-peritoneal shunt (VPS) is the most widely used neurosurgical procedure to treat patients with hydrocephalus. Reported five-year shunt survival rates for first-time shunt implantations are as low as 53.1% [9, 19, 41]. Up to 25% of patients suffering from idiopathic normal pressure hydrocephalus (iNPH) develop primary deterioration after VPS. Neurosurgical Review extended neuroimaging does not yield a cause for shunt malfunction in patients presenting with nonspecific symptoms. The valve itself as the origin of the shunt malfunction may come to the fore. The aim of our study was to clarify whether in patients requiring shunt revision, without a final yield in prior diagnostics, the valve itself might contribute to the malfunction of the shunt system or not
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