Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
2000-03-17
2002-09-17
Dvorak, Linda C. M. (Department: 3739)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C600S383000, C600S561000, C606S129000
Reexamination Certificate
active
06453185
ABSTRACT:
BACKGROUND
The invention generally relates to an improved catheter and a method for treating conditions of the brain area and, more particularly, to an improved ventricular catheter adapted for placement in a subdermal tunnel, and a method for sensing physical parameters in the skull area with a ventricular catheter and placing the catheter in a subdermal tunnel in an improved manner to expedite the subdermal placement procedure and to reduce the risk of infection.
Head injuries, other pathologic neurological disorders and systemic diseases have been shown to cause acute swelling of the brain or an increase in the volume of cerebral spinal fluid (“CSF”). The so-called “closed-box” cranial vault restricts the amount of increase that can be tolerated before the increase in intracranial pressure poses a danger to the patient. The contents of the cranial vault are essentially non-compressible and comprise approximately 80% brain, 10% CSF and 10% blood. An increase in one of the components requires a decrease in one or both of the others to accommodate the change. An increase in the brain or CSF may result in undue pressure on healthy tissue resulting in temporary or permanent disability to the patient. Intracranial pressure sensors, catheters and shunts have been developed to monitor and manage the treatment of these patients, either through the recording and manipulation of information from the sensor or through the shunting mechanism from a catheter in the ventricle.
The intracranial pressure monitoring devices are introduced into the brain through an access hole in the skull. When placement in the ventricle is desired, the opening is appropriately close to the anterior horn of the lateral ventricle and the catheter and/or sensor is inserted through the access hole into the ventricular space. The pressure sensor in the distal end of the catheter conducts information via a cable in the catheter to an external monitor. Simultaneously, fluid may be drained from the ventricle and collected in an external drainage bag or system to relieve pressure. The monitoring and management of the patient may be hours or many days, typically five to ten days.
Because of the extended amount of time that the ventricular catheter must be positioned in the patient, and because of the invasive nature of the procedure, another consideration is the increased risk of infection of brain tissue by pathogens entering through the skull opening or access hole. The presence of a direct pathway through the skull access hole from an outside environment directly into the brain ventricle causes a substantial risk of infection. To reduce this risk, a catheter placement technique referred to as subdermal tunneling has been developed.
In the prior fluid-filled pressure sensing catheter approach, a foil strain gauge or rosette of strain gauges is located at the proximal end of the catheter or within an apparatus outside of the catheter. The distal end of the catheter is inserted into the cranium and receives fluid from the cranium in a lumen extending completely through the catheter to the proximal end. The fluid pressure in the catheter lumen acts on the surface to which the gauges are attached and the gauge or gauges provide an electrical signal representative of the strain in the surface which can be correlated to pressure in the cranium.
In this fluid-filled catheter approach, traditional or forward tunneling under the scalp is typically used. A surgeon makes an incision, or first opening, in the patient's scalp exposing a portion of the skull overlying a ventricle of the brain. Subsequently, a twist drill access hole is formed through the skull exposing the interior of the cranial vault. Next, the distal end of the fluid-filled catheter is inserted into the twist drill access hole after which the proximal end of the catheter is connected to a sharp pointed tunneling instrument, such as a trocar or needle. The trocar is inserted under the scalp at the point of incision just proximal of the skull access hole and is advanced through the scalp to form a subdermal tunnel of typically five or more centimeters. The tunneling instrument is pulled through the tunnel to exit the scalp at this exit opening. The proximal end of the catheter, which is attached to the end of the trocar, is also pulled through the tunnel and is then pulled taut in the tunnel. The surgeon then sutures the scalp over the skull access hole and over the tunnel entrance and exit thereby sealing the skull access hole and the scalp openings.
The diameter of the tunnel is kept as small as possible and is just larger than the diameter of the catheter that must be threaded through the tunnel. The small diameter of the tunnel contributes to lowering the risk of infection. It has been found that the subdermal tunnel technique substantially decreases the risk of intracranial infection by providing an elongate tunnel through which pathogenic organisms would have to pass before they could enter the cranial vault through the skull access hole. There is thus no direct pathway for contamination to enter the access hole. The tunneling technique has proven very successful.
One of the drawbacks of a fluid filled catheter is that the pressure head created by the fluid column in the catheter must be subtracted from the pressure readings to get an estimate of the actual CSF pressure within the brain ventricle. The common use of oscillating beds in head injury cases further complicates this problem by causing fluctuations in the fluid column. To solve the pressure measurement problem associated with fluid filled catheters, transducer tipped catheters that include sensors, typically strain gauges or optical sensors, placed within the catheter's distal end were developed.
Transducer tipped catheters used in ventricle pressure sensing have a transducer of an electrical or optical nature located at the distal tip of the catheter, that is placed within the cranium of the patient. There is an elongate shaft connecting the catheter's distal end with its proximal end. The proximal end of the catheter includes a connector that is used to connect the internal optical or electrical conductors to another connector located on an intermediary cable or directly on an instrument for displaying the pressure sensed or other physical parameter that has been sensed to the physician and nursing staff. Such connectors not only interconnect the signal communication line, but also provide a physical device that locks the two connectors together to apply the necessary pressure to force the internal conductor of one connector into good signal contact with the internal conductor of the other connector, and so that they do not become inadvertently disconnected. Because of this locking device and other design parameters of prior connectors, they have been too large to fit within the small subdermal tunnel discussed above. Therefore, transducer tipped catheters have been reverse tunneled.
Reverse tunneling is similar to traditional tunneling except that the trocar is used to puncture the scalp at a location distal of the skull access hole and is tunneled towards the skull access hole from the distal location. After formation of the subdermal tunnel, the distal end of the catheter, which is smaller than the connector, is inserted into the second scalp opening (remote from the skull access hole) and pulled through the tunnel to the scalp opening adjacent the skull access hole. The needed length of catheter is pulled through the tunnel in the direction of the skull access hole up to the point that the large connector or other device mounted to the catheter cannot be pulled farther. The large connector will either come into contact with the distal scalp opening or, if partially pulled into the tunnel, will be prevented from further advancement due to its larger size as compared to the smaller diameter of the tunnel. The physician then positions the distal end of the catheter in the ventricle or other cranial location as desired and the catheter is fixed in the desired in-dwelling positi
Dvorak Linda C. M.
Fulwider Patton Lee & Utecht LLP
Integra LifeSciences Inc.
Ruddy David M.
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