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FAQ's
VBAS was born of the desire to eliminate the
need to “pull” on brain tissue as this is dangerous with current brain
retractors that cause a high local retraction pressure distributed over
a limited surface area. The VBAS was designed to eliminate any “pulling”
on surrounding tissues in any direction. By their circumferential
elliptical design as well as the hemispheric design, there is no need to
pull in any direction whatsoever. The limited pressure exerted on the
surrounding brain tissue is a neutral one, and we believe is far less
than the pressures that cause venous compromise and resultant cerebral
damage. The design of the VBAS was to maximize the surface area of
displaced brain to reduce the local tissue pressure.
VBAS was also designed to function as an IGS pointer, so that problems
related to brain shift due to surgical manipulation might be eliminated.
In combination with minimally invasive techniques, the problems of
volume shift, cortical shift and target tissue shift are minimized and
surgeon confidence in IGS enhanced.
VBAS is simple in design and easy to use.
The combination of ease of use, navigational capability and reliability
will allow for increased surgeon comfort and confidence in the use if
IGS technology.
 When
will VBAS be used
Does
the VBAS have any limitations
What
do you think about VBAS & IGS-supported retractor positioning
What
are the safety constraints
What
about bleeding, is this a concern
When will VBAS be used
The TC device will be impressive for use in posterior fossa tumors such
as large acoustic neuromas and meningiomas when an internal
decompression approach is used. Because the distal margins of these
tumors tend to remain fixed to dura or bone during internal
decompression, navigational guidance during removal allows for safety to
surrounding structures and prevention of traversal tumor margins
inadvertently. The TC device also provides for excellent access for far
lateral approaches to the foramen magnum and C1/C2 region in the removal
of tumors etc. The small port TC model (12mm) is also ideally suited for
removal of intracerebral hematomas, third ventriculostomy, colloid cyst
excision etc.
We strongly feel that the small port TC model will compete successfully
with endoscopic approaches currently being popularized because it offers
both neuronavigational capability and binocular vision by way of a truly
minimally invasive approach that stands up to endoscopic claims.
We believe the EC model allows for impressive exposure to lesions around
the brain, such as meningiomas (subtemporal, subfrontal, falcine,
inferooccipital etc.), posterior fossa aneurysms requiring a subtemporal
approach, trans-callosal approaches to intraventricular tumors.
Through further development with additional products in the pipeline, we
believe we will for the first time allow for a minimally invasive
approach to anterior circulation aneurysms and trans-sylvian approaches
to posterior circulation aneurysms to provide both navigational
confidence and a better exposure than possible with most large
craniotomy, extensive sylvian dissection approaches. The view is truly
impressive. The retraction problems that commonly occur after anterior
communicating artery aneurysm surgery are also eliminated.
We believe to also be able to offer a significant advantage whereas most
aneurysms can be included in the elliptical working channel: in cases
where intraoperative aneurysmal rupture occurs, bleeding is contained in
the working channel itself, thus preventing diffuse dispersion of
subarachnoid blood while the problem is being brought under control. The
SF will also provide minimally invasive neuronavigational access to
tumors along the base such as sphenoid wing and cavernous meningiomas,
large supra-sellar pituitary tumors and craniopharyngiomas.
Does the VBAS have any limitations
None, which we can see. The access port can be easily manoeuvred,
particularly with IGS capability. The field of view is in fact
impressive, and surrounding tissues are nicely visualized through the
optically transparent working channel.
Sylvian fissure approaches with the products in the development pipeline
provide superior visibility with a smaller craniotomy and greatly
reduced risk of retraction injury.
We feel that keyhole surgery is made both safer and simpler with VBAS.
.
What do you think about VBAS & IGS-supported retractor
positioning
As far as we know, light does not turn around corners; therefore, most
approaches require a direct path to the target. We agree that VBAS will
not be able to compete with the flexible endoscope, when such
manoeuvrability is required. However, we believe that the improved
working channel of the VBAS will make endoscopic use easier when it is
required.
We feel most strongly that the ability of an
access device to “become” the navigational device, so that both
access-without-displacement and navigation occur simultaneously,
provides for a “10” in both functionality and safety. Such functionality
will remove to a large degree the concerns of neurosurgeons that worry
about brain-shift targeting issues in a non-real-time IGS working
environment.
What are the safety constraints
The VBAS is made of polished polycarbonate and slides very easily along
brain tissue. It does not adhere to tissues, even after prolonged
periods of time. Therefore, interposed materials are no longer necessary
to protect the brain from adhesion to the access device. We do; however,
recommend that the access port be lubricated with saline prior to
positioning.
The VBAS is designed for minimally invasive neurosurgery. The field of
view is actually quite impressive, as mentioned under the “Does VBAS
Have Any Limitations” question, above. The “step-by-step” approach is in
fact superior to the standard corticotomy approach. As mentioned above,
no retraction or pulling is required during positioning of the TC
device. The beauty of the TC device is that it eliminates brain shift,
allowing for straight path to the target without lateral displacement of
the brain or target. For each centimeter of depth of placement, the
amount of brain displacement is far less with the TC device than would
be required with standard retraction. A lesion at depth would require a
larger corticotomy and definite lateral brain shift with standard
retractors.
Meticulous hemostasis is standard of care in brain surgery. As the
polished polycarbonate tubular surface does not adhere to the
surrounding brain, removal does not cause bleeding, as occurs with the
removal of cotton etc. after prolonged periods of time with standard
retraction systems.
An advantage by design of the VBAS system is obtained in the optical
clarity of the polished polycarbonate so that if hemorrhagic change or
bleeding occurs in the surrounding tissue during a procedure, it can be
visualized as it happens and addressed immediately. Standard retractors
and the foam or cotton materials placed beneath and around them are
opaque. When bleeding occurs when they are utilized, it is not seen
immediately, and sometimes hemorrhagic change in surrounding brain is
not recognized until the end of the procedure when the retractor and
materials are removed. Any vessels outside the access device can be
plainly seen, whereas they can not be seen with standard opaque
retraction systems. As the working port is advanced, oncoming vessels
can be seen through the optically clear introducer, and therefore
avoided accordingly.
Since the VBAS does not cause overdue brain compression, the need to
reposition a standard retractor and “control” local pressure has been
alleviated. This should make for a calmer and more confident surgical
experience.
What about bleeding, is this a concern
Visualization of bleeding as it occurs is a concern, and is addressed by
the optical clarity of the VBAS devices. It allows for an immediate
response to the problem when it occurs.
The concept of a distally expandable working channel is a good one,
particularly when larger lesions at depth are considered in the
subarachnoid space. Such capability could be incorporated in future
modifications of VBAS.
Vycor Medical is currently underway with certifying that our products
are MRI/MRA compatible. Another design consideration for using
polycarbonate rather than metal is that transmission of electrocautery
energy is not possible with plastic devices, thus eliminating the
possibility of electrical burning of exposed tissues.
The following is a graphed chart of 15 neurosurgeons responses to the
following questions:
We believe that VBAS will allow those
surgeons who avoid brain retraction to prevent brain injury (larger
craniotomy, more extensive exposure and dissection) to use a brain
access system with improved safety and neuronavigational capability. We
also believe that those who avoid neuronavigational technology because
of fears of brain-shift targeting issues that occur with standard
retraction systems will become more comfortable with VBAS as a method
fro using IGS.
We believe that those surgeons who use IGS
will all be in the “10” range once they have had a chance to use the
VBAS/IGS integrated devices. This information was obtained by viewing
ONLY the SLA prototypes. These neurosurgeons had not tried the VBAS
System.
Preplanning results in simplified surgery. When accuracy and targeting
doubts are allayed in the minds of doubtful surgeons, IGS utilization
will rise.
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