1. Field of the Invention
This invention relates to the design, construction, and use of a device for acute and chronic measurement of intracranial pressures in the human central nervous system, particularly during magnetic resonance (MR) imaging procedures, in particular during the injection or infusion of therapeutic drugs into the brain parenchyma. The present invention is an improvement over conventional methods and apparatus for measuring intracranial pressure, such as ventriculostomy with an external transducer, epidural strain gauge transducer, pressure sensitive epidural capsule, pressure sensitive subdural capsule, or subarachnoid pressure transducer.
2. Background of the Prior Art
Elevated intracranial pressure (ICP) can result from a variety of pathophysiological disturbances and frequently presents a major problem in the management of patients with head injury or other neurological disorders and diseases, including brain tumors and intracerebral hemorrhage. Although numerous autoregulatory and compensatory mechanisms protect the brain against elevations in ICP, if the ICP is increased to levels approximately equal to or greater than those of the arterial blood pressure, cerebral blood flow can be severely compromised leading to brain herniation and death.
The primary aim of ICP monitoring is to provide an early warning of a deteriorating condition so as to enable corrective therapy to be implemented. The accuracy required when measuring ICP is typically of the order of 1-2 mm Hg, but equally important is the reliability of the data. To ensure reliability, the calibration of any measuring device must be easily checked and adjusted as necessary. In addition to the steady-state accuracy of any sensing device and recording system, it is essential to have adequate dynamic response characteristics in the measuring device.
It is also essential that measurements can be made with minimum interference to the patient. To satisfy this objective, non-invasive methods of determining changes in ICP indirectly have been attempted using, for example, impedance plethysmography. Such non-invasive methods have been used successfully in neonates. However, in adults, methods which give the most accurate measurements require access into the cranial cavity and are therefore more invasive.
Invasive ICP devices have generally evolved in two basic directions. The first is based on implanting a sensor within the cranium. The second is based on mounting the sensor externally and connecting the measurement site through a fluid-filled transmission line. The three main sites for ICP Ring are the lateral ventricle, the extradural space, and the subdural or subarachmoid spaces.
U.S. Pat. No. 4,014,319 to Favre discloses an intracranial pressure transducer comprising a small sealed capsule positioned in a trephined hole in the patient""s skull, wherein a sensor diaphragm in contact with the dura mater is displaced by changes in intracranial pressure and produces an output signal proportional to the change in intracranial pressure. U.S. Pat. No. 4,026,276 to Chubbuck discloses a pressure monitoring apparatus implantable in the cranium, wherein the apparatus comprises a passive resonant circuit with inductance and capacitance capability for measuring intracranial pressure by comparison to a reference ambient pressure.
U.S. Pat. No. 4,062,354 to Taylor et al. discloses an intracranial pressure transducer system comprising a holding bracket containing sensor elements which is positioned against the dura of the brain, wherein the elements within the holding bracket transmit electromagnetic signals related to the intracranial pressure to a receiver outside the patients body.
U.S. Pat. No. 4,080,653 to Barnes et al. discloses a method and apparatus for recording intracranial pressure utilizing a transducer amplifier.
U.S. Pat. No. 4,114,603 discloses an intracranial pressure monitoring device comprising a pressure-sensitive catheter insertable between the dura mater and arachnoid membrane. U.S. Pat. No. 4,114,606 discloses a monitoring apparatus for intracranial pressure measurement, wherein electromagnetic radiation is imposed on a passive circuit implanted in the cranium, the frequency at which the radiation is absorbed reflecting intracranial pressure.
U.S. Pat. No. 4,147,161 to Ikebe et al. discloses a system for measuring or monitoring intracranial pressure which comprises a non-elastic detecting pouch inserted between the skull and the brain, wherein a pressure measuring device in the liquid in the pouch indirectly measures the intracranial pressure.
U.S. Pat. No. 4,156,422 to Hildebrandt discloses an apparatus for treating hydrocephalus comprising housing which contains subcutaneously implantable components for measuring and controlling fluid pressure, wherein a second housing outside the patient contains measuring and control components whereby an intracerebral space may be automatically drained in response to a predetermined adjustable ICP.
U.S. Pat. No. 4,210,029 to Porter discloses a differential sensor unit utilizing fiber optic light guides, wherein three light guides pass within a pneumatic line into one end of a rigid cylindrical envelope implanted in the skull. Detectors are arranged to actuate pressure display and pneumatic controls to adjust the internal pressure of the envelope to match the ICP and thereby measure the ICP. U.S. Pat. No. 4,265,252 to Chubbuck discloses an implantable transsensor device containing a passive RF resonant circuit which is responsive to changes in ICP.
U.S. Pat. No. 4,385,636 to Cosman discloses an implantable telemetric differential pressure sensing device comprising a planar closed conductive loop which moves with a flexible diaphragm, wherein the resonant frequency of the conductive loop is detected telemetrically to determine pressure in a body compartment.
U.S. Pat. No. 4,343,038 to McKean discloses a magnetic field generator and magnetic pick-up coil contained in an implanted ICP monitoring device. U.S. Pat. No. 4,354,506 to Sakaguchi et al discloses an intracranial pressure gauge which comprises a powerless resonance circuit composed of a coil and a condenser, a sensor equipped with an implantable pressure-sensitive section capable of changing the inductance or the capacitance of the condenser in response to a change in ICP. U.S. Pat. No. 4,438,773 to Letterio discloses an implantable subarachnoid bolt for use in measuring ICP. U.S. Pat. No. 4,465,075 to Swartz discloses an integrated circuit including a pressure transducer and temperature compensation circuit.
U.S. Pat. No. 4,471,786 to Inagaki discloses a telemetering intracranial pressure transducer for detecting ICP, wherein a pressure-receiving layer disposed in contact with the dura mater transmits an output signal to an telemetering transmission circuit housed entirely beneath the patients scalp.
U.S. Pat. No. 4,600,013 to Landy et al. discloses a probe for ICP measurements in the subarachnoid space, said probe comprising a threaded shaft having a lumen in contact with a pressure transducer.
U.S. Pat. No. 4,621,647 to Loveland discloses an apparatus for monitoring and regulating ICP, wherein a manometer, transducer and regulator are interconnected by tubing and stopcocks. U.S. Pat. No. 4,627,443 to Chubbuck discloses an X-ray readable implantable pressure sensor,,wherein shifting of the radiopaque means is observed to indicate the change in pressure of a body cavity.
U.S. Pat. No. 4,677,985 to Bro et al. discloses an intracranial probe to monitor both ICP and blood flow by thermal diffusion and hydrogen clearance techniques.
U.S. Pat. No. 4,703,757 to Cohen discloses an optical fiber pressure transducer, wherein variations in transversely applied pressure to an elongated flexible fiber results in proportional light refraction and corresponding output signal.
U.S. Pat. No. 4,711,246 to Alderson discloses a miniaturized pressure transducer, wherein light transmitted through a single optical fiber is reflected by a diaphragm in accordance with the pressure being measured.
U.S. Pat. No. 4,723,556 to Sussman discloses an intracranial ventricular catheter assembly, wherein a pressure sensing device is connected to the proximal catheter. U.S. Pat. No. 4,738,267 to Lazorthes discloses an implantable intracranial pressure sensor, wherein a pressure-sensitive diaphragm placed directly on the dura mater transmits the intracranial pressure through a resistive type transducer. U.S. Pat. No. 4,772,257 to Hakim et al. discloses an external programmer for magnetically-adjustable cerebrospinal fluid shunt valve.
U.S. Pat. No. 4,858,619 to Toth discloses an intracranial pressure monitoring system, wherein relief valves are combined with a pressure sensor for automatic venting of cerebrospinal fluid during elevated ICP.
U.S. Pat. No. 4,805,634 to Ullrich discloses an adapter assembly for accurately positioning a removable biosensor implanted in the cranium.
U.S. Pat. No. 4,841,986 to Marchbanks discloses a method and apparatus for measuring ICP, wherein a pressure sensor placed against the eardrum indirectly detects ICP changes based on displacement of the eardrum.
U.S. Pat. No. 4,903,707 to Knute et al. discloses a ventricular catheter assembly comprising a catheter and a bolt, wherein the catheter can be inserted to a predetermined depth into the cranium. U.S. Pat. No. 4,995,401 to Bunegin et al. discloses a device for measuring anterior fontanelle pressure, wherein ICP changes can be detected noninvasively.
U.S. Pat. No. 5,000,049 to Cooper et al. discloses an apparatus for measuring fluid pressures using a catheter device.
U.S. Pat. No. 5,005,584 to Little discloses a fiber optic transducer utilizing a flexible membrane to transduce pressure by interrupting light transmission between fiber optic paths in a catheter or guide wire carrier.
U.S. Pat. Nos. 5,074,310 and 5,117,835 to Mick disclose a method and apparatus for in non-invasively measuring changes in ICP , wherein a predetermined vibration signal is applied to one location in the skull and an output vibration signal is detected from another location in the skull reflecting ICP changes over time.
U.S. Pat. No. 5,108,364 to Takezawa et al. discloses a monitoring catheter for medical use comprised of multiple tubes equipped for fluid delivery and removal, pressure measurement, and temperature measurement. U.S. Pat. No. 5,113,868 to Wise at al. discloses a pressure sensing catheter system comprising a catheter, a pressure sensor, and a signal conduit means within the catheter for signals between an external monitor and the pressure sensor, the signal conduit including two electrical conductors which are connectable to the external monitor.
U.S. Pat. No. 5,191,898 to Millar discloses a cerebroventricular catheter means of measuring ICP and injecting or withdrawing cerebrospinal fluid, wherein a transducer positioned at the end of the cerebroventricular catheter and electrically coupled to a monitor allows for ICP monitoring.
U.S. Pat. No. 5,292,899 to Watanabe et al. discloses a method for measuring ICP by using a device comprising a reservoir implantable under the skin of a patient and into which reservoir cerebrospinal fluid can be introduced from the ventricle of the patient, a flexible dome configured to be upwardly projected from said reservoir by the pressure of the cerebrospinal fluid and flexibly deformable according to an external force, a pressing part for pressing against said dome through the skin, a pressing-part-driving means for driving said pressing part pressing the dome and a flexible membrane provided at the tip of the pressing part and having an interior filled with a fluid, the method comprising: pressing the flexible membrane of the pressing part against the dome of the reservoir through the skin by means of the pressing-part-driving means after a zero point correction of the pressure transducer is performed by communicating the interior of the flexible membrane with the atmosphere.
U.S. Pat. No. 5,325,865 to Beckman et al. discloses a catheter assembly for measuring fluid pressure in a body cavity, comprising an optical converter responsive to an electrical power source for energizing a light-emitting diode which has drift characteristics which vary in response to temperature, and a detection circuit. U.S. Pat. No. 5,230,338 to Allen et al. discloses an interactive image-guided system for displaying images corresponding to the placement of a surgical probe in the body. U.S. Pat. No. 4,173,228 to Van Steenwyk et al, and U.S. Pat. No. 5,042,486 to Pfeiler et al. disclose medical probes wherein electromagnetic signals are propagated between one antenna on the tip of the probe inserted into a body region and several antennae outside the body. The position and orientation of the probe tip are determined from the signals transmitted between said antennae.
U.S. Pat. No. 5,211,165 to Dumoulin et al., U.S. Pat. No. 5,255,680 to Darrow and Dumoulin, U.S. Pat. No. 5,307,808 to Dumoulin et al., and U.S. Pat. No. 5,318,025 to Dumoulin et al. additionally disclose a tracking system in which radiofrequency signals emitted by an invasive device, such as a catheter, are detected and used to measure the device""s position and orientation in a patient. Localization of devices in situ is achieved by transmit radiofrequency coils positioned at its distal end, which are detected by receive radiofrequency coils positioned around the imaging volume of interest. The position of the device, as determined by the tracking system, is superimposed upon independently acquired diagnostic images. U.S. Pat. No. 5,383,454 to Bucholz discloses a system for indicating a position of a tip of a probe which is positioned within an object on images of the object, wherein a computer employing translational software translate the position of the tip of said probe into a coordinate system corresponding to the coordinate system of the cross-sectional images.
Each of the above cited patents provide advantages and disadvantages for ICP monitoring. For instance, intraventricular catheters are accurate but may be difficult to position in the presence of brain swelling and shifting of tissue. Subarachnoid devices are easily placed, but may underestimate higher ICP pressures, particularly if they are not coplanar to the brain surface. Epidural devices require placement through a burr hole and can be hampered by recording artifacts, dampening, and problems with calibration.
Moreover, none of the above cited patents disclose a method or apparatus for evaluating changes in ICP resulting from the direct injection or infusion of drug agents into brain tissues. One of the significant problems with direct drug delivery to living tissue is assuring that the drug is accurately distributed to target receptor locations. The efficacious delivery of therapeutic agents for the treatment of brain tumors or neurodegenerative diseases, as two examples, requires that the agents be delivered as close to their receptors in the brain as possible, while minimizing increases in intracranial pressure during and after drug delivery. Liquid drug agents delivered into the brain through implanted catheters will disperse from the site of injection at variable rates depending on a number of factors, including the physicochemical characteristics of the drug, capillary uptake, metabolic degradation and excretion of the drug, size of the extracellular space (the volume fraction), and geometry of the brain cell microenvironment (tortuosity). The degree to which each of these factors influences the distribution of a particular drug agent may be an important determinant of the effectiveness of drug treatment of diseases of the central nervous system.
Ideally, drug material injected into the brain infiltrates the extracellular space, and the subsequent tissue distribution of the drug is governed mainly by its molecular weight, molecular radius, and the tissue matrix structure into which the material has been injected. However, injection of a solution containing a macromolecular drug agent into the intraparenchymal extracellular space of the brain may instead result in the injected drug being sequestered as a cavity or depot. If the injected drug solution forms a fluid-filled cavity in the tissue, this may lead to tissue selling, an increase in ICP and, secondarily, altered interstitial transport of the drug solute.
It is therefore apparent that increases in ICP induced by intraparenchymal injections of liquid drug agents can injure tissues directly, or indirectly by retarding the efficacious distribution of the drug due to tissue swelling and retarded interstitial solute transport. Thus, it is important to be able to monitor any local and regional increases in ICP resulting from injections of liquid drug agents directly into the brain parenchyma. The availability of an MR-visible drug delivery device which incorporates a method means for monitoring local and regional changes in ICP would make it possible to obtain near real-time information on tissue pressure changes during interventional procedures in an intra-operative MR system.
The present invention discloses a device and method for monitoring intracranial pressure (ICP) during MR image-guided neurosurgical procedures, wherein an MR-compatible microsensor pressure transducer coupled to a pressure sensing diaphragm is positioned or located on the surface of an interventional device, such as at or near either a) a distal tip of the device and b) lateral surfaces of an MR-compatible device such as an MR-compatible multi-lumen drug delivery catheter. One or preferably more than one sensing element may be present on the interventional device. The microsensor and diaphragm detect and monitor local and regional changes in ICP during and after delivery (especially immediately after delivery while changes in local concentration of the injectant or drug agents can be observed) of liquid drug agents into the brain parenchyma. In at least one method within the scope of the invention, the pressure sensor includes a pressure transducer for converting a sensed pressure into a first electrical signal which is detectable by an external monitor transmission after transmission over a signal conduit means. There may be a first switching device for selectively controlling when the first electrical signal is generated, and a device that is responsive to at least one command signal from the external monitor for controlling the delivery of drug solution in response to detected alterations in ICP. In a practice of the present invention, the ICP monitoring device may also be inserted into any convenient location such as a lateral cerebral ventricle, cerebral cistern, subarachnoid space, subdural or extradural space, or venous sinus, under MR imaging guidance, and used to record intracranial pressures over seconds, minutes, hours to days in patients undergoing diagnostic or therapeutic neurologic interventions. Continuous monitoring of the ICP in real time may also be effected in this invention.
The invention also relates to an apparatus for the determination or monitoring of intracranial pressure comprising:
an article that is insertable into the tissue or vasculature of the brain,
said article comprising a pressure sensing element, a signal transmitting connector connecting the pressure sensing element and a signal reader (meaning artificial intelligence or artificial memory such as a reader, recorder or analyzer), the signal reader being able to (read, record, or analyze) signals from said pressure sensing element to indicate hydrostatic pressure or changes in hydrostatic pressure. The pressure sensing element may, for example, comprise a solid state pressure sensing element, a curved semiconductor element, or a physical sensor, alone or combined with electronic or electrical elements, such as a diaphragm (e.g., a diaphram or flexible, compressible, deflatable, inflatable or pressure moveable layer or element that has one surface that is exposed to an environment in which the pressure sensing element is placed, such as within the fluid or tissue fluid of a patient), as where a second surface of the diaphragm defines part of an internal cavity within the pressure sensing element, and movement of said diaphragm causes changes in pressure within the internal cavity. A pressure reading device may then be present within said internal cavity and the pressure sensing element is attached to the connector by electrical attachment of the pressure reading device to the connector. The pressure-sensing device may be connected to or independent of a device for the delivery of chemical agents into the bodily fluid, and particularly into the bodily fluids of the brain. Certain semiconductor elements are known to be pressure-sensitive, and therefore semiconductor elements may be positioned on the interventional device at the tip and/or at multiple locations on the lateral surface of the interventional device and be electrically connected to an outside source to interpret the signals.
At least one method according to the present invention for sensing the intracranial pressure within a patient comprises inserting the above described apparatus into the brain of a patient, visualizing the tissue around the apparatus and visualizing the apparatus itself by magnetic resonance imaging particularly in effect by continuous or real time visualization with MRI or fluoroscopy, less preferred), and positioning the apparatus within the device under magnetic resonance imaging, and reading signals from said pressure sensing element to indicate hydrostatic pressure or changes in hydrostatic pressure within the brain during or shortly after delivery of chemical agents into the fluids and/or tissue of the brain. Upon reading changes in hydrostatic pressure of the brain that exceeds a predetermined amount, an indication of the exceeding of that predetermined amount may be provided to an operator of the apparatus, as by an alarm, special image on a video screen, or by an automatic function change directed by memory (computer) associated with the system. For example, the apparatus may also comprise at least one lumen for delivery of chemicals to the patient, and chemicals are delivered to the patient through the at least one lumen, and upon reading changes in hydrostatic pressure of the brain that exceeds a predetermined amount during delivery of chemicals to the patient from the lumen, an indication of the exceeding of that predetermined amount is provided to an operator of the apparatus. This can be effected upon the indication of the exceeding of that predetermined amount by an artificial memory, that artificial memory then signaling the apparatus to reduce the amount of chemical being delivered to the patient.
One aspect of this invention is to provide a device and method for acute measurement of ICP in the human central nervous system during magnetic resonance (MR) imaging procedures, particularly those involving direct injection or perfusion of drugs into the brain parenchyma, with the measurement and sensing being performed during those stages of the drug delivery where pressure changes may occur.
A second aspect of this invention is to provide a device and method for controlling the delivery of drug solution in response to detected alterations in ICP during magnetic resonance (MR) imaging procedures, particularly those involving direct injection of drugs into the brain parenchyma. This can be particulartly accomplished by the use of at least two pressure sensing elements, one distal and one proximal to the point of insertion of the interventional device. By having separated pressure sensing devices, a pressure gradient may be measured and/or the direction of flow and variations in flow from the point of introduction can be determined.
A third aspect of this invention is to provide a device as an alternative method for the detection and measurement of intracranial pressure, replacing devices and methods such as conventional ventriculostomy with an external transducer, an epidural strain gauge transducer, a pressure sensitive epidural capsule, a pressure sensitive subdural capsule, or a subarachnoid pressure transducer.
A fourth aspect of this invention is to provide a device and method to record intracranial pressures over extended time periods such as hours or days in patients that have been subjected to compression or shift of the cerebral ventricles resulting from severe head injury, tumor, or other causes of acute or chronic intracranial hypertension.
A fifth aspect of the invention is to provide a device and method to accurately record ICP in the lateral ventricle, epidural, subdural, and subarachmoid spaces in patients in whom these fluid-filled cavities have been compressed by trauma or medical condition, including tumors or hematoma, or may have thick or mobile walls or small volumes that cannot be reliably penetrated with standard ventricular catheters when they are attempted to be positioned under stereotaxic guidance.
A sixth aspect of this invention is to provide a device and method for safely measuring ICP with minimal risk of infection caused by meningitis or ventriculitis, minimal risk of intracranial hemorrhage from opening the dura or puncturing the ventricle, and minimal interference to the patient.
A seventh aspect of this invention is to provide a device and method for MR image-guided therapeutic drainage of cerebrospinal fluid to relieve acute rises in ICP.
An eighth aspect of this invention is to provide a device and method for injection of a small volume of MR-visible gas for MR-ventriculography while monitoring ICP.
A ninth aspect of this invention is to provide a device and method for a hydrocephalus pressure valve and self-sealing port for regulating the flow of cerebrospinal fluid through the catheter after placement of the catheter tip into the ventricle, subarachnoid, subdural, or epidural space under MR imaging guidance.
A tenth aspect of the present invention is to provide a device substantially made of MR-visible elastomeric hydrogel, polymer, thermoplastic, or similar low friction material to minimize abrasive damage to the brain during insertion.