Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-12-01
2003-08-19
Paik, Sang (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C607S112000, C607S116000
Reexamination Certificate
active
06609020
ABSTRACT:
The present invention relates to a neurosurgical guide device for use in neurosurgery. The device is particularly useful in stereotactically targeted surgical treatment of abnormalities of brain function, including abnormalities of movement such as Parkinson's disease, chorea, tremor, multiple sclerosis and cerebral palsy; abnormalities of the mind including depression, obsessive compulsive states and Alzheimer's disease; chronic pain syndromes and epilepsy. The device can also be used in the targeted treatment of brain tumours.
In order to perform neurosurgery, the surgeon needs, in the first instance to localise the desired target. This is conventionally achieved by fixing a stereotactic reference frame to the patient's head, which can be seen on the diagnostic images and from which measurements can be made. The stereotactic frame then acts as a platform from which an instrument is guided to a desired target using a stereoguide that is set to measure co-ordinates. Once an instrument is guided to the desired target, treatment can begin. For example, where the instrument is an electrode, the target area can be functionally neutralised by controlled heating at the electrode tip (radio-frequency lesioning), or by delivering high frequency electrical stimulation to the target through a chronically implanted deep brain stimulation (DBS) electrode.
Other instruments that can be used include catheters, probes for monitoring brain metabolic or electrical activity. In recent years fetal cells have been implanted into the brains of patients with Parkinson's disease using stereotactic techniques and function has been successfully restored. Drugs or tropic substances (such as nerve growth factor) may also be delivered at a targeted intraparenchymal site. Such drugs and tropic substances will modulate and may restore brain function when delivered stereotactically using catheters targeted to the desired site.
A number of difficulties are encountered in such neurosurgical procedures. Including sub-optimal placement of the instrument which may lead to significant morbidity or failure of the treatment. Sub-optimal placement may result from brain shift during the operative procedure, deflection of the instrument as it passes through the brain substance to the desired target or may result from miscalculation by the surgeon.
In order to confirm accurate target localisation preoperatively, the surgeon typically guides a microelectrode to the target to record characteristic neural firing patterns and/or pass a stimulating electrode to the target site to locally depolarised neural tissue and create a reversible functional lesion. These procedures are generally performed when the patient is awake so that functional change can be observed. A common problem with these techniques is that the passage of an electrode into or through the target will cause a mechanical lesion which will disrupt neural firing at the target site and may cause a fictional improvement. In view of this, the surgeon can lose the necessary teed-back for accurately placing the electrode. This effect is termed “impact effect”.
If the surgeon does successfully identify the target site with the electrode, then the process of removing the electrode and replacing it with an instrument (which may be a lesioning or DBS electrode), may lead to an error in the positioning of the end of the instrument due to brain shift. The instrument may create a new tract through the brain, follow the tract of another test tract to a sub-optimal target site, or sinking of the brain due to loss of the cerebro spinal fluid (CSF) may result in placement of the instrument above the optimal target site.
Furthermore, if the surgical treatment is a thermal lesion, the surrounding tissue becomes acutely swollen. The swollen tissue will be functionally inactivated and so an undersized lesion with surrounding swelling that is confined to the target will give a good functional result during the post operative period. However, the benefits will fall off as the swelling settles and the surgery may need to be repeated. Typically, up to 20% of patients require repeated surgery at the same target site.
Brain tumours may be targeted for treatment by the interstitial implantation of radio-isotopes into the tumour, or the implantation of a catheter into the tumour to deliver anti-tumour agents. As with functional neurosurgery, difficulties with established techniques include per-operative brain shift which may result in radiation or the anti-tumour agents being delivered to a sub-optimal site and damaging normal tissue.
When treating a tumour with interstitial radiotherapy an “after loading” method is typically employed in which a catheter is stereotactically inserted to the target and brought out through the scalp where it is secured using a fixation sleeve which is attached to the scalp. Radionuclide seeds such as Iodine 125 are placed in an inner catheter and this is then “after loaded” into the fixed catheter for a treatment period of days or weeks. Because this system is externalised, there remains a significant risk of infection tracking into the brain and causing morbidity. Furthermore, because the catheter is secured to the scalp, there can be some movement which may lead to delivery to a sub-optimal site.
U.S. Pat. No. 5,954,687 discloses a burr hole ring for use with a catheter, wherein the burr hole ring engages the skull. The burr bole ring is sealed by a septum and does not allow the insertion of medical instruments into the brain along a specific trajectory.
U.S. Pat. No. 4,840,617 discloses a catheterization apparatus for delivering oxygenating nutrients to or from the cerebral-spinal fluid of a patient.
U.S. Pat. No. 5,713,858 discloses a permanently implanted catheter. The catheter is sealed via a septum and does not enable insertion of instruments along a desired trajectory.
U.S. Pat. No. 5,116,345 discloses an apparatus for implanting an instrument into a brain. The device requires the positioning a temporary skull bolt that protrudes above the scalp of a patient leading to problems with the stability of the device and possible infection. The device does not allow repeated access to a desired target site over a prolonged period of time.
U.S. Pat. No. 5,180,365 discloses an implantable infusion device which cannot be used for inserting instruments along a defined trajectory.
U.S. Pat. No. 5,927,277 discloses an apparatus for securing medical devices within a cranial burr hole. The device does not allow the insertion of an instrument along a defined trajectory to a desired target site.
The present invention provides a neurosurgical guide device comprising a tube for insertion into a brain of a patient to the vicinity of a desired target, wherein the tube has a head attached to one end thereof, the head having a passageway therethrough in communication with the bore of the tube and which terminates in an opening on the outer surface of the head, and having one or more formations on its external surface for securing the device in a hole formed in a skull of the patient, whereby an instrument can be introduced through the opening and passed along the bore from a proximal end to a distal end thereof.
The neurosurgical guide device of the present invention can be used in functional neurosurgery or other stereotactic surgical procedures wherein an instrument has to be inserted to a specific target site in the brain of a patient.
The guide device of the present invention is sized and configured for receiving a neurosurgical instrument. The term “a neurosurgical instrument” or “instrument” as used herein refers to any instrument which can be used in a neurosurgical procedure. Preferably the instrument is a deep brain surgical instrument. It is particularly preferred that the instrument is an electrode such as a lesioning or stimulating electrode, a catheter, or a probe such as a microdialysis probe for the metabolic state, an electrode for measuring the electrical state or a pressure transducer.
The head of the guide device of the present inve
Paik Sang
Pearne & Gordon LLP
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