Surgery – Instruments – Electrical application
Reexamination Certificate
2001-09-06
2004-07-13
Rollins, Rosiland (Department: 3739)
Surgery
Instruments
Electrical application
Reexamination Certificate
active
06761718
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to ventricular catheters which have been previously implanted in-vivo into one or more ventricles of the human brain for therapeutic purposes; and is particularly directed to removing adherent tissue occlusions of ventriculoperitoneal shunts employed in pediatric neurosurgical techniques for release and fluid flow of cerebral-spinal fluids
BACKGROUND OF THE INVENTION
The present invention is usefully employed with ventricular catheters which have been therapeutically implanted in-vivo into the human brain; but which have become blocked by the surrounding cranial tissue which has occluded the intake drainage holes within the implanted catheter and become adherent to the catheter itself. In order to properly appreciate both the medical problem and the improved bipolar coagulator device which is employed therapeutically to alleviate such occlusion conditions in-situ, an in-depth description of the relevant medical and therapeutic use circumstances is provided below.
A. Ventricular Catheterization
The four ventricles of the human brain are interconnected cavities that produce and circulate cerebral-spinal fluid (CSF). Procedures involving ventriculostomy (i.e., placement of a catheter into the ventricular system of the brain) form a major part of a neurosurgeon's clinical practice. General areas for application of ventricular catheter placement include intracranial pressure monitoring (ICP), draining or shunting of CSF and the installation of pharmacological therapeutic agents.
CSF drainage is a major life-sustaining therapy for patients with congenital or acquired hydrocephalus. CSF drainage, which can only be performed with an intraventricular catheter, is a life-preserving procedure, because it can immediately reduce intracranial pressure. The ventricular catheter, used to drain cerebral-spinal fluid, is connected to a peripheral subcutaneous drainage system, i.e., to the peritoneal cavity or systemic circulation via the heart. However, later catheter obstruction by tissue and debris is a common, sometimes life-threatening problem.
Standard procedures for ventricular catheterization are disclosed in the textbook literature. See, for example, Neurosurgery, edited by Robert H. Wilkins and Setti S. Rangacharty, Section A, Chapter 13, Techniques of Ventricular Puncture (McGraw Hill 1984).
A frequently chosen site for ventricular catheterization is the coronal plane. In most cases, a catheter is inserted in the anterior horn of the lateral ventricle through an orifice or burr hole drilled just anterior to the coronal suture in the midpupillary line of the cranium, i.e., in the frontal bone over the ventricle. This is known in the field as Kocher's point. The burr hole, only slightly larger than the diameter of the selected catheter to insure a snug fit and provide a seal against CSF leakage, is placed approximately 1 cm, anterior to the coronal suture, approximately 10 to 12 cm. above the nasion, and approximately 2 to 3 cm. from the midline over the nondominant hemisphere. After the burr hole is made, the dura and underlying pia-arachnoid are opened and coagulated, for example, with a fine-tipped blade after cauterizing the dural surface.
A pre-measured catheter having a stylet is then introduced and directed freehand through the burr hole, approximately in the coronal plane, and angled towards the medial canthus of the ipsilateral eye, using external landmarks such as the inner canthus of the eye in the frontal plane and a point just in front of the external auditory meatus in the lateral plane as guides to placement. CSF should flow freely from the catheter tip at a depth of approximately 4 to 5 cm. from the interior cranial surface.
A distinctive “give”, or release of opposition, can often be felt when the ventricle is penetrated. Pressure should be measured at this point, since an artificially low value will be obtained even if small amounts of fluid are lost. Then, after removal of the stylet from the catheter, advancement another 1 cm. or so should insure placement in the frontal horn at a depth of about 5 to 6 cm. from the external table of the skull, care being taken that CSF continues to flow.
A variety of ventricular catheters and a range of methods for guiding a catheter into the ventricular system of the human brain are conventionally known and used. Merely illustrating this range and variety are: U.S. Pat. Nos. 5,569,267; 5,030,223; 4,860,331; 4,613,324; 4,392,307; 4,386,602; 3,934,590; 3,223,087; 3,073,310; 3,053,256; 3,817,887; and the references cited within each of these printed publications.
B. Ventriculoperitoneal Shunts
Ventriculoperitoneal (VP) shunt placement for hydrocephalus is one of the most common procedures in neurological surgery. Hydrocephalus may result from subarachnoid hemorrhage, trauma, tumors, and the like. The technique entails introducing a catheter through brain tissue into one of the lateral ventricles of the brain. Cerebrospinal fluid in the ventricle may be vented through the catheter to relieve signs, symptoms, and sequelae of hydrocephalus.
The current surgical technique for placement of VP shunts was developed in the 1950s by Scarff and has persisted with few modifications. Despite the relative simplicity of this procedure, the complication rate can be significant and includes operative morbidity as well as post-operative infections and tissue obstructions.
Surgical technique plays a major role in reducing complications associated with VP shunts. Improper placement of the ventricular catheter may result in neurologic injury from the misplaced catheter or may cause an early proximal shunt obstruction, which is often secondary to blockage by adherent choroid plexus and other debris. The incidence of misplaced catheters is variable and dependent on a variety of factors, including the experience of the surgeon, the size of the targeted ventricle, the surgical approach, and the use of intraoperative guidance, such as fluoroscopy, ultrasound, or endoscopy. Thus, to optimize shunt function and minimize morbidity proper placement of the proximal catheter is essential.
Two surgical approaches have been principally used for VP shunt placement, frontal and parieto-occipital. To assist in placement into small ventricles, a frontal catheter guide has been developed by Ghajar for placement of frontal ventricular catheters [Ghajar J B, J.
Neurosurg.
68: 318-319 (1988)]. This instrument capitalized on the anatomical observation that a line passing perpendicular to the skull at the coronal suture will intersect the lateral ventricle.
However, parieto-occipital catheter placement has some advantages over frontal catheter placement. The catheter path necessary for the frontal approach to the ventricles traverses frontal lobe regions having a low seizure threshold. Mechanical irritation of the neural tissue surrounding the catheter may give rise to epileptogenic foci independent of the underlying cause of hydrocephalus. This complicates patient management and increases health care cost, as well as markedly impacting the patient's quality of life.
The anatomy of the head and neck also cause technical difficulties for the surgeon. The distal end of the shunt is subcutaneously tunneled to the peritoneal cavity for implantation. Implantation in the open peritoneum provides an outlet for excess fluid drainage from the ventricles. The catheter path to the abdomen is circuitous from the frontal burr hole, however. The tube must pass posterior to the ear, and generally requires an additional skin incision. These difficulties frequently cause major complications and tissue obstructions.
C. Intraventricular Shunt Occlusions and Obstructions
Although generally successful and widely accepted by both neurosurgeons and patients, the ventriculoperitoneal shunt (“VPS”) and indeed all shunting systems, regularly malfunction despite the best efforts of physicians and biomedical engineers. These malfunctions—once commonly the result of material, construction, or mechanical failures—
Children's Medical Center Corp.
Prashker David
Rollins Rosiland
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