<jjs> wrote in message news:13tvd7fa2iccc4e@news.supernews.com...
> "granny" <DontSpamMe@NoSpam.com> wrote in message
> news:47df648c$0$17362$4c368faf@roadrunner.com...
>
>> Could you explain please what this new 'Zone System' is with step by
>> step instructions...
>
> Sure, just as soon as you post step-by-step instructions for brain
> surgery


APPARATUS AND METHODS FOR PERFORMING BRAIN SURGERY

A less invasive surgical technique for performing brain surgery in which
a dilating obturator and cannula assembly is inserted into brain tissue
until the obturator tip and cannula are adjacent the target tissue. The
obturator is removed and surgery is performed through the cannula. In
preferred embodiments the obturator and cannula are placed using image
guidance techniques and systems to coordinate placement with
pre-operative surgical planning. A stylet with associated image guidance
may be inserted prior to insertion of the obturator and cannula assembly
to guide insertion of the obturator and cannula assembly. Surgery
preferable is performed using an endoscope partially inserted into the
cannula with an image of the target tissue projected onto a monitor.

The brain is a delicate soft tissue structure that controls bodily
functions through a complex neural network connected to the rest of the
body through the spinal cord. The brain and spinal cord are contained
within and protected by significant bony structures, e.g., the skull and
the spine. Given the difficulty of accessing the brain through the hard
bony protective skull the diagnosis and treatment of brain disorders
presents unique challenges not encountered elsewhere in the body.
Diagnosis of brain disorders requires clear, accurate imaging of brain
tissue through the skull. In recent years significant advances have been
made in imaging technology, including stereotactic X-ray imaging,
Computerized Axial Tomography (CAT), Position Emission Tomography (PET)
and Magnetic Resonance Imaging (MRI). See, for example, Butler U.S.
Patent 6,359,959. These imaging devices and techniques permit the
surgeon to examine conditions within the brain in a non-invasive manner
without opening the skull. If a target lesion or mass is identified
through use of one or more imaging techniques, it may be necessary or
desirable to biopsy a lesion within the brain.

Once a diagnosis has been reached based upon one or more imaging
techniques, a treatment plan must be developed. One available method of
treatment involves X-ray therapy

Alternatively, surgical treatment may be necessary or desired. In order
to operate surgically on the brain, access must be obtained through the
skull and delicate brain tissue containing blood vessels and nerves that
can be adversely affected by slight disturbances. Therefore, great care
must be taken in operating on the brain not to disturb delicate blood
vessels and nerves so that adverse consequences do not resxilt during or
after surgery. Brain surgery can be highly invasive. In some instances,
in order to obtain access to target tissue, a substantial portion of the
skull is removed and entire sections of the brain are retracted to
obtain access. Of course, such techniques are not appropriate for all
situations, and not all patients are able to tolerate and recover from
such invasive techniques. It is also known to access certain portions of
the brain by forming a hole in the skull, but only limited surgical
techniques may be performed through such smaller openings. In addition,
some techniques have been developed to enter through the nasal passages,
opening an access hole through the occipital bone to remove tumors
located, for example, in the area of the pituitary.

A significant advance in brain surgery is stereotactic surgery involving
a stereotactic frame correlated to stereotactic X-ray images to guide a
probe or other smrgical instrument through an opening formed in the
skull through brain tissue to a target lesion or other body.

A related advance is frameless image guidance, in which an image of the
surgical instrument is superimposed on a pre-operative image to
demonstrate the location of the instrument to the surgeon and trajectory
of further movement of the probe or instrument.

A preferred apparatus for accessing brain tissue has a dilating
obturator with a blunt distal tip, a substantially cylindrical shaft
portion, and a proximal handle portion. A cannula is disposed around the
shaft portion and preferably is made of a transparent material. The
obturator and cannula assembly preferably is associated with an
image-guided surgery system so that placement of the obturator and
cannula assembly can be carefully monitored and controlled as the
obturator and cannula assembly is atraumatically inserted into brain
tissue.

In a first embodiment the obturator has a longitudinal channel
therethrough configured and dimensioned to receive the shaft of a narrow
stylet or probe. The stylet or probe has attached thereto image guidance
means calibrated to indicate the orientation and position of the stylet
or probe. An image guidance system interacts with the stylet or probe to
display for the surgeon on a monitor an image of the stylet or probe
superimposed onto an image of the patient s brain, such as an MRI image.
The image may be a pre-operative MRI image used for surgical planning.
When the stylet or probe is mounted in the longitudinal channel of the
obturator, the superimposed image of the probe also is indicative of the
position and orientation of the dilating obturator and the cannula.

Traditional methods are used to incise and retract soft tissue of the
scalp covering the skull. A hole is made in the skull, and the dura is
opened and retracted to provide access to the brain. In the first
method, the stylet or probe is inserted through the obturator
longitudinal channel and advanced until a length of the stylet or probe
extends out of and beyond the blunt tip of the dilating obturator. The
dilating obturator and cannula assembly is held back away from the
tissue as the stylet or probe is gently advanced through the brain
tissue under both direct vision and positional image guidance until the
tip of the stylet or probe is adjacent the target tissue. Once the
stylet or probe is placed and the position is confirmed using the image
guidance system, the blunt dilating obturator and cannula assembly is
slowly and carefully advanced into the brain tissue to atraumatically
spread the tissue over the dilating tip and around the cannula while
maintaining the position of the stylet or probe as a guide to
advancement of the obturator and cannula assembly. A gentle back and
forth rotation during insertion may facilitate placement of the
obturator cannula assembly. Preferably, the cannula is clear so that the
dilated brain tissue may be visually inspected through the walls of the
cannula to assure that no damage was caused to surrounding brain tissue
during insertion of the device.

Alternatively, in a second contemplated method the image guidance means
may be mounted directly to the dilating obturator and cannula assembly
so that the obturator and cannula assembly may be inserted without a
separate stylet or probe. In this configuration, the obturator and
cannula assembly is inserted into the brain tissue under image guidance
until the obturator is adjacent the target tissue. Once the obturator
and cannula assembly is positioned, the dilating obturator is removed,
leaving the cannula in place.

In yet a third contemplated method, the dilating obturator and cannula
assembly may be inserted into the brain under direct visualization
without use of an image guidance system.

After the cannula is placed, surgery may be performed through the
cannula, either under direct vision or more preferably using an
endoscope and camera system to project an enlarged image of the target
tissue onto a monitor to visualize the tissue during surgery.

Preferably, the cannula has a diameter of approximately 10 mm to 20 mm,
and more preferably 10 mm to 15 mm. An endoscope of a substantially
smaller diameter, such as a 4 mm endoscope, is mounted partially
inserted into the cannula. The endoscope is mounted to one side of the
cannula and inserted so that the image projected onto the monitor is of
the target tissue at the end of the cannula. In practice, a 4 mm
endoscope inserted approximately halfway into the cannula is appropriate
to create the desired image display while leaving a substantial portion
of the cannula open and available for the insertion of instruments to
perform surgery. Optionally, a camera holder may be used to secure the
endoscope in the desired position.

Appropriate surgical instruments are then used to perform surgery upon
the target tissue. For example, scissors, graspers and suction tools may
be inserted through the cannula, visualizing the tips of the instruments
to perform the desired procedure either directly with the naked eye or
through a microscope, or indirectly through the endoscope using the
endoscope eyepiece or more preferably and camera system to display the
image on a monitor. A preferred instrument for debulking brain tissue is
a fluidized ultrasonic instrument, such as CUSA

During surgery, monitoring equipment may be used to monitor brain
function during surgery to assist the surgeon in understanding the
effects of the actions taken during surgery operating on the brain so
that the surgery may be terminated in the event an indication of an
adverse effect is detected.

After surgery upon, the target tissue is complete, the cannula is gently
removed, and the dura, skull and scalp are closed in a traditional
fashion.

Gentle atraumatic dilation of the brain tissue makes it possible to
operate further inside the brain than otherwise would be possible
utilizing traditional surgical techniques. The disclosed methods and
apparatus create an access area to work while simultaneously protecting
adjacent brain tissue from, inadvertent collateral damage and trauma
that might otherwise occur if more traditional surgical techniques were
to be utilized. In addition, accessing target tissue through the cannula
as contemplated avoids more invasive techniques that involve removing
substantial portions of the skull and retracting large portions of the
brain to gain access to operate on target tissues. In some cases, the
devices and methods may make it possible to operate on target tissue
that would, without these devices and methods, otherwise be regarded as
inoperable using previously known techniques.

The techniques described herein are particularly useful to access
tumors, cysts or other conditions which might otherwise be considered
inoperable or might require much more invasive transcranial surgery to
remove a larger portion of the skull and retract a substantial amount of
brain tissue. The techniques described herein using dilating obturator
and cannula permit brain surgery to be performed in a less invasive
manner through an opening in the skull that is substantially smaller
then otherwise possible, on the order of a 2 cm to 4 cm in diameter
rather than a much larger opening for more traditional surgical
techniques.

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