gms | German Medical Science

60th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Benelux countries and Bulgaria

German Society of Neurosurgery (DGNC)

24 - 27 May 2009, Münster

Implantation failures and suboptimal positions of gravitational valves. Rather the rule than the exception – with a massive impact on shunt dysfunction

Meeting Abstract

  • B. Vienenkötter - Neurochirurgische Klinik, Universitätsklinikum Heidelberg
  • A. Unterberg - Neurochirurgische Klinik, Universitätsklinikum Heidelberg
  • A. Aschoff - Neurochirurgische Klinik, Universitätsklinikum Heidelberg

Deutsche Gesellschaft für Neurochirurgie. 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien. Münster, 24.-27.05.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocP16-02

DOI: 10.3205/09dgnc423, URN: urn:nbn:de:0183-09dgnc4239

Published: May 20, 2009

© 2009 Vienenkötter et al.
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Outline

Text

Objective: The function of gravitational (g)-valves is strictly dependent on the angle of vertical alignment. Therefore they require an orientation strictly parallel to the longitudinal body axis. Despite its decisive role only 1 out of 166 g-valve-papers (incl. running studies) systematically investigated g-valve-deviation from body axis (= flaw angles). Furthermore, the implantation site on the lateral head has not been compared to the thoracic site.

Methods: From our medical record of about 650 g-valve-implanted patients with retroauricular and thoracic gravitational devices, each 50 consecutive patients were extracted and randomized. On scout-scans / x-rays the deviations against the body axis were measured. The impact on g-valve-function and the additional effect of 30° head elevation were calculated.

Results: Only 22% of retroauricular vs. 28% of thoracic implantations were correctly placed (flaw angle <10°). Cranially placed valves showed anteversion in 84% and retroversion in 16%. The mean deviation was 21° implying a valve-offset of 72mm H2O in a 200mm H2O-g-valve, the maximum was 43° (valve-offset: 136mm H2O). A nocturnal head elevation of 30° may result in a mean valve-offset of 156mm H2O calculated with the mean deviation angle, and 191mm H2O in the worst case. In thoracic position the mean deviation was 10° in lateral and 16° in antero-posterior direction implying a valve-offset of 55mm H2O in a 200mm H2O-valve. Maximal deviation was 52° resulting in valve-offset of 158mm H2O.

Conclusions: Positioning failures are common in our series and may indicate malfunction of g-valves. The thoracic implantation site is clearly superior to the head position and should therefore be preferred in adults.