Untersuchung über die Feingewebs-Fremdkörperinteraktion an internen Bauteilen und Oberflächen von Liquor-Shuntventilen
by Constantin Reitemeyer
Date of Examination:2023-02-17
Date of issue:2023-02-17
Advisor:Prof. Dr. Hans-Christoph Ludwig
Referee:Prof. Dr Arndt Schilling
Referee:PD Dr. Sabine Sennhenn-Kirchner
Persistent Address:
http://dx.doi.org/10.53846/goediss-9725
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Abstract
English
The mankind is accompanied by the hydrocephalus for thousands of years. Archaeological finds of hydrocephalic skulls date back to 10.000 BC (Flannery and Mitchell 2014). It is a serious disease of the Central Nervous System, which can occur at any age and can lead to death if left untreated. The cerebrospinal fluid builds up in the cerebral ventricles, leading to increased intracranial pressure and to macrocephaly, especially in infancy (Trepel 1995). This leads to symptoms such as headache, vomiting, nausea and cognitive impairment. Adequate therapy in form of the implantation of a ventriculoperitoneal shunt (VPS) to drain the excess of cerebrospinal fluid exists since 1955. The shunt consists of a silicone catheter and a valve and connects the cerebral ventricles to the peritoneum or right atrium. On average every second shunt system has to be replaced during its lifetime due to complications (Reddy et al. 2014). The occlusion of a VPS valve is responsible for this malfunction in 56.1 % of the cases (Sainte-Rose et al. 1991). The drainage of excess cerebrospinal fluid stops due to occlusion, through which intracranial pressure increases and symptoms are triggered. A revision in which the affected components or the entire shunt are replaced will then be unavoidable. The aim of our study was to get a better understanding of the mechanism of shunt occlusions. Tissue proliferations (Blegvad et al. 2013), calcifications and mineralizations (Echizenya et al. 1987) on inner and outer surfaces of shunt catheters and valves as reasons for an occlusion have already been described in literature. However, by using the ,,Trenn-Dünnschliff-Technik“ (sawing and grinding technique), we were able to histologically analyze tissue within titanium valves for the first time and gain knowledge about its quantity and localization. Cellular tissues were detected in almost every valve (Table 19). In eight out of nine cases, when the clinical diagnosis indicated a valve occlusion, a subtotal or total obstruction was confirmed histologically. The thickness and composition of the tissue layer correlated primarily with the duration of the implant in vivo. Implants that were explanted after a few weeks showed only single cells or cellular traces. With longer in vivo periods of implantation, multilayered tissue structures in form of layers, plaques or conglomerates were found. These were mainly localized on the corners and edges of the valve or the rotor, on the ball or the niches next to the ball-cone-unit. The proteins laminin, fibronectin and collagen IV were detected by immunohistological examinations of the preparations. These extracellular matrix proteins are components of the basal membrane. They are expressed by the processes or astrocytes and form the blood-brain barrier and the Virchow-Robin space under physiological conditions. We were able to show that individual cells and whole cell clusters adhered to the inner surfaces of the valves. It has already been described in the literature that microvascular trauma caused by implantations and the ongoing foreign body irritation cause the activation of astrocytes and microglial cells and a chronic inflammatory reaction (Harris und McAllister 2012). We suspect that this irritates fibrosis within the valve and can lead to failure of the entire system after a longer period of implantation. As a consequence of our study we conclude that an early therapy of intraventricular hemorrhage using neuroendoscopy is very important to reduce the stimuli for membrane and scar formation. This will reduce shunt dependency. However, since the insertion of a shunt cannot be completely avoided in the foreseeable future, optimization of the shunt therapy is necessary in order to reduce the revision rates. The lavage is therefore currently the subject of a worldwide study (Trophy-Registry).
Keywords: hydrocephalus; ventriculoperitoneal shunt; valve obstruction; shunt complication; shunt valve; cerebrospinal fluid shunt; astrogliosis; shunt revision; neurosurgery