gms | German Medical Science

Objective: Diagnosis of symptomatic valve malfunction in hydrocephalic patients treated with VP-Shunt (VPS) is still a challenge. Clinical symptoms such as headache or nausea are unspecific, hence cerebrospinal fluid over- or underdrainage can only be suspected but not proven. Knowledge concerning valve dysfunction is still limited. We aim to provide data on the flow characteristics of explanted shunt valves in patients with suspected valve malfunction.

Methods: An in vitro shunt laboratory setup was used to analyze the explanted valves under conditions similar to those in a ventriculo-peritoneal shunt system. The differential pressure (DP) 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.

Results: Twelve valves of different types (three Codman CertasPlus, four Miethke gravity-regulated Shuntassistant, three Codman Hakim programmable valve, two DP-components of the Miethke proGAV 2.0 valve) from eight patients (four male) with internal hydrocephalus were explanted between 2016 and 2017. Four patients suffered from idiopathic normal pressure (iNPH), three patients from posthemorrhagic and one patient from obstructive hydrocephalus. Bonferroni-adjusted post-hoc analysis revealed a significant difference (p < 0.001) of the flow rate between each explanted shunt valves and their corresponding reference valve, at each DP.

Conclusion: In all patients with suspected valve malfunction, significant alterations of flow rates were demonstrated, verifying a valve deficiency, 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.