<jjs> wrote in message

"granny" wrote in message

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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