Article Type : Research Article
Authors : Abdulwahab F Alahmari
Keywords : Ventriculoperitoneal shunt; Obstruction; Hydrocephalus; Siphon shunt
The aim of this paper is to propose a cleanable ventriculoperitoneal shunt (VP shunt) system that uses simple methods to reduce shunt
replacement operations due to obstructions.
Cerebrospinal fluid (CSF) is produced by choroid plexus
normally a 500 cc / day. The flow of the CSF in hydrocephalus is
disturbed wither by an over production of CSF, or an obstruction
in the pathways, or a weak absorption of the CSF in the arachnoid
granulations in the superior sagittal sinus (SSS). The
hydrocephalus can be communicated (i.e. the ventricular system
connected with the subarachnoid space) or non-communicated
(i.e. the ventricular system is not connected with the subarachnoid
space due to an obstruction). One of the treatments for
hydrocephalus is using a Ventriculoperitoneal Shunt (VP shunt).
A VP shunt can work in best cases for two years, then the patient
will need to undergo a surgery to remove the shunt and replace it
with a new one . Usually, a VP shunt will malfunction due to
an infection or an obstruction . The aim of this paper is to
propose a new VP shunt design that will decrease the chances of
needing to go to a shunt replacement surgeries.
The shunt is design to allow a full access to the entire shunt length by placing two accesses that allow going to one direction. One of the accesses is opened cranially and one is opened caudally. The tube is passing subcutaneously until it opens with two accesses behind the ear. The cleaning accesses must be in a rubber or plastic box behind the ear which has the same skin color of the patient. The hygiene of this area (i.e. access area) is very important for the patient’s health. The area must be kept dry and clean especially after taking showers or swimming. The skin on the edges of the access must be regularly checked and cleaned with a disinfectant. The abdominal part of the VP shunt has multiple openings, one is the main big two opening and the rest of them are accessory openings that are design to allow more flow. There are two cleaning wires; one for the cranial tube and one for the abdominal tube. Each tube’s wire has a red mark showing the length of the tube. During cleaning the insertion of the cleaning wire should not cross the red mark. Crossing the red mark on the wire can allow the wire to hit the brain parenchyma (i.e. in cleaning the cranial part of the tube) and cause bleeding or cause penetration of the abdominal wall or intestinal perforation (i.e. in cleaning the abdominal part of the tube). The catheter is made from stainless steel which is thick, flexible, and strong to be impenetrable, while using the cleaning wire. Cleaning the tube will help in cleaning and removing the accumulating protein on the tube’s wall. Sometime, a broken part of the choroid plexus is vacuumed into the VP shunt which causes shunt obstruction which can be removed by the cleaning wire. The catheter is coated with poly methyl methacrylate (PMMA) inner and outer surface of the tube which prevent infection & inflammation in the tube and works to prevent adhesion of the CSF protein to the catheter wall which will lead to obstruction. Practically, stainless steel can be coated with plastic. The whole shunt is one part so no shunt disconnection will occur and is made of flexible stainless steel so it can’t be broken (i.e. shunt fracture). Before start removing the obstruction, the access area must be cleaned and sterilized very well to prevent cerebral infections. A good implanting of the sterilization and cleaning of the area before start the cleaning will eliminate any chance of cerebral infection. Some VP shunts use a flashing technique to remove the choroid plexus which can lead to inter?ventricular hemorrhage due to high pressure or make an impression on the brain due to repeated flashing. As well, flashing to an obstructed tube inside a region that already contains high intracranial pressure can cause death
Figure 1: The design of the VP shunt which can be modify to have only one cranial catheter.
Figure 2: The VP shunt located behind the ear and its fixed (red sign) to the skull bone to prevent malposition
Figure 3: The holes on the distal end of the abdominal part of the shunt. The design of these openings is convergence from inside to outside of the tube as illustrated in the figure to minimize the flow from outside to inside the tube.
Figure 4: The neurosurgeon should stops at the red sign at the wire to prevent
Figure 5: The superior location of the tip of the VP shunt which will work in standing and supine position.
Figure 6: The method of fixation of the VP shunt
Figure 7: A one way valve located in the abdominal part of the VP shunt to prevent any return of abdominal fluid and allow the cleaning wire to pass to the last part of the tube.
Figure 8: An illustration of the VP shunt which has no devices or battery attached to it.
The “S” shaped siphon filter will prevent air from entering the
tube until it has a high pressure to overcome the CSF which will
prevent any Airlock in the tube. The tip of the ventricular part of
the shunt is placed in a superior location at the roof of the lateral
ventricle to prevent siphon effect which will lead to subdural
hematoma. The tube can has two cranial heads or one based on
the necessity. The two heads will decrease the chances of an
obstruction to occur. The siphon shape will prevent any siphon
effect “over?drainage” of the CSF because the tip of the tube is
placed in a superior position in both lateral ventricles which will
work in a standing or supine position. Both tubes are fixed to the
skull firmly to prevent any displacement of the tube. The
neurosurgeon who is placing the VP shunt must make sure of the
accurate position of the shunt and the fixation of the shunt to the
skull very well to avoid displacement of the shunt. The VP shunt
has a one way valve in the abdominal part of the shunt to prevent
any return of any fluid from the abdominal cavity to the brain.
The one way valve will allow cleaning of the abdominal part of
the shunt. In cases of shunt obstruction of the cranial part, a
trendelenburg position must be applied which may remove the
obstruction. If did not work, a cleaning wire of the shunt is
required. The one way valve will prevent of any fluid return from
the abdomen in the trendelenburg position. Flashing of normal
saline might be used in trendelenburg position. If that maneuver
did not work, the neurosurgeon in charge can start using the wire
cleaning technique. The benefit of this shunt is decreasing the risk
of having any cranial part obstruction by 50%. The cranial part of
the shunt usually is the most obstructed part. As well, due to
presence of too many holes on the distal part of the abdominal
part, it will decrease the percent of having an obstruction in the
abdominal part of the shunt. The shunt is very cheap because it
has no technology, digital devices, or battery see (Figures 1-8).
This design needs to be tested, evaluated in a clinical trial, then
get approved by the Food and Drug Administration (FDA). The
design theoretically will decrease the chances of tube obstruction
in the cranial part by 50% by placing two cranial parts. The
cleaning process of the VP shunt will required a thorough
cleaning process to prevent any infection. A firm fixation of the
shunt to the skull will prevent any shunt?malposition. The shunt
will be very cheap and it has no technologies or digital devices.