Adjustable gravitational valves. From the conception in 1996 to first implantations 2008
Authors: Alfred Aschoff, Michael Kiefer, Uwe Kehler, Bahram Hashemi, Andreas Unterberg
Background
In 1975 Hakim conceived and Schulte constructed the first
gravitational (g)-valve, which used implemented balls for a
position-dependent automatic adjustment of the valve-resistance, in
order to compensate the hydrostatic overdrainage in upright
position. In spite of excellent tests in vitro the Hakim-Lumbar was
rarely used and had no commercial success, probably due to an
exclusive design for lumboperitoneal shunts. In addition the
obligate vertical orientation was difficult to achieve because of
the round valve body. In the early 90's the forgotten concept was
rediscovered simultaneously by Richard/Block, Affeld/Miethke,
Aschoff, Sophysa and Chhabra and let to numerous new g-valves with
a superior handling.
In 1991 the combination of g- with adjustable valves was
proposed and realized in 1993 (Aschoff). Since 1994 they were
routinely implanted by an increasing number of users. Actually
about 40 g-valve-studies show reduced quotes of clinical relevant
overdrainage; subdurals requiring evacuations count 20-30% only
compared to conventional valves. However an inappropriate selection
of pressure ranges with consecutive g-valve revisions remained a
problem. In 1996 the author suggested adjustable g-valves and
developed 2000/1 seven detailed technical solutions. The idea was
picked up by Miethke, who patented the first ProSA in 2004 and an
improved version, which passed the CE-tests in 2008.
Materials and Methods
The ProSA implies an excenter fixed on a magnetic rotor, which
varies the tension of a spring counteracting the weight of a
gravitational ball. The opening pressure in vertical can be changed
stepless between 0-40 cmH2O. A brake excludes unintentional
readjustments by magnets and MRI up to 3 T. The implantation is
possible on sternum or lateral head. Like all g-valves a strict
vertical orientation to the longitudinal body axis is essentially.
The ProSA can be combined with any simple DP- or adjustable
valves.
Results
Since 12/2008 until now 15 implantations were clinically
successful (actualized data follow in June). Three of them with
decompensating complicated hydrocephalus had a perioperative
ICP-measurement; all showed physiological ICPs in upright and
horizontal.
Conclusions
Adjustable g-valves are a consequent further development of
shunt technology and verifiable effective in vivo. A prospective
multicentre trial is launched (Kehler/Kiefer 08).
University of Heidelberg, Department of Neurosurgery. Im
Neuenheimer Feld 400, 69120 Heidelberg
Email: Alfred_Aschoff@med.uni-heidelberg.de
