GB2042685A

GB2042685A - Valve in a Surgically Implantable Shunt System for Venting Cerebrospinal Fluid

Info

Publication number: GB2042685A
Application number: GB8000217A
Authority: GB
Original assignee: Hakim Co Ltd
Current assignee: Hakim Co Ltd
Priority date: 1979-01-10
Filing date: 1980-01-03
Publication date: 1980-09-24
Also published as: CA1150588A; SE8000178L; FR2446112B1; FR2446112A1; GB2042685B; JPS55113457A; DE2951025A1; NL8000019A

Abstract

The valve (10) has an elongate, hollow valve body (11) into which a flat plate (14) tightly fits partitioning the valve body into an outlet chamber (16) and an inlet chamber (17) communicating respectively with a drainage catheter and a cerebroventricular catheter (12). The flat plate has a circular aperture (18) connecting the chambers and upon which rests a spherical ball (19). A flat spring (20) biases the ball against the circular periphery of the aperture. Testing for leakage is accomplished by illuminating with light of a suitable frequency the aperture (18), with ball (19) seated therein, and detecting any light transmitted through the aperture. <IMAGE>

Description

SPECIFICATION A Surgically Implantable Shunt System for Venting Cerebrospinal Fluid This invention relates to a surgically implantable shunt system for venting cerebrospinal fluid (CSF) from a cerebroventricular catheter to a drainage catheter and more particularly to such a system including a valve for presenting a precisely controllable back pressure to the cerebral ventricles in case of hydrocephaly and similar conditions of impaired circulation and absorption of cerebrospinal fluid.

Mechanical devices for controlling the drainage of cerebrospinal fluid into the bloodstream are in use, an example of which is the shunt device of U.S. Patent No. 3,288,142. These devices include valves such that the flow is unidirectional from the ventricles to drainage into the circulatory system. While quite successful, such valves are relatively expensive and difficult to fabricate.

These prior valves are also somewhat heavy and bulky, their metal parts interfering, for example, with X-ray scanning procedures. Previously known devices also sometimes become clogged with brain debris or with CSF protein when elevated to abnormally high levels. This is particularly true of so-called slit valves which have been used for this purpose, e.g. valves which are merely a thin slot in a silastic tube. Such debris can prevent the valve from sealing properly, thereby degrading its ability to regulate closely the back pressure presented to the cerebral ventricles. Wide hystersis between opening and closing pressures has been another shortcoming of known shunt valves for use in treating hydrocephaly, i.e. there has not been a well defined "popping" pressure at which pressure the valve opens.

The present invention provides in a surgically implantable shunt system for venting cerebrospinal fluid from a cerebroventricular catheter to a drainage catheter, a valve for presenting a precisely controllable back pressure to the ventricles, said valve comprising an elongate, hollow valve body, a flat plate partitioning said valve body so as to form an inlet chamber and an outlet chamber, said ventricular catheter being coupled to said inlet chamber and said drainage catheter being coupled to said outlet chamber, said plate being provided with a circular aperture connecting said inlet and outlet chambers, a spherical ball of diameter larger than said aperture for controllably restricting flow through said aperture, and a spring including a cantilevered flat portion overlying said ball and biasing it against the circular periphery of said aperture whereby a circular seal is selectively effected between said ball and said plate, providing a precisely defined back pressure with low hysteresis and low susceptibility to bridging by debris.

The shunt system is designed for use in a hydrocephalus treatment system, for example, as shown in Fig. 1 of U.S. Patent No. 3,527,226.

Testing of known valves has been accomplished previously by subjecting the valves to a vacuum or a gas pressure, or even exposure to a liquid environment. These methods are cumbersome, time consuming and often foul the valve in the testing process.

According to the present invention, the effectiveness of the valve seal is tested during manufacture by optical means. Thus, according to the present invention, light energy at a wavelength for which the ball is opaque is directed upon the aperture with ball in place.

Absence of light leakage indicates a properly sealing valve.

A specific embodiment of the present invention will now be described by way of example, and not by way of limitation, with reference to the accompanying drawings in which.~ Fig. 1 is a partial longitudinal sectional view of a surgically implantable shunt system of the present invention: Fig. 2 is a sectional view along section lines 2-2 of Fig. 1; Fig. 3 is an edge view of the flat plate portion of the valve device; Fig. 4 is a plan view of the flat plate portion of the valve device; and Fig. 5 is a schematic representation of an optical method for testing the sealing effectiveness of the valve device.

Corresponding reference characters indicate corresponding parts through the several views of the drawings.

Referring now to the accompanying drawings, the valve device 10 comprises a hollow valve body 11, preferably made of injection molded polyethersulfone plastics. Valve body 11 ouples at its inlet end to cerebroventricular catheter 12, and its outlet end with drainage catheter 13 or with a pumping system, including a second valve, i.e. in the manner shown in U.S. Patent No. 3,527,226.

Tightly fitting within valve body 1 1 is a thin, flat plate 14, preferably made of stainless steel, which partitions valve body 1 1 into an inlet chamber 15 and an outlet chamber 16. In this embodiment, thin plate 14 is 0.38 inch long, 0.14 inch wide and 0.01 inch thick. A highly polished circular aperture 1 7 of diameter 0.057 inch is cut through flat plate 14 thereby connecting inlet chamber 15 and outlet chamber 16 providing a flow path for cerebrospinal fluid from the cerebral ventricles to drainage into the circulatory system. As can be seen more clearly in Fig. 3, circular aperture 17 in flat plate 14 has a coined rim 18, the radius of curvature of which matches the radius of spherical ball 19, thereby providing a seat for ball 19. In this embodiment, the radius of curvature of rim 18 is approximately 0.031 inch.The combination of valve body 1 1 and thin plate 14 allows this shunt valve to be light in weight, compact and inexpensive to manufacture.

Spherical ball 19 for controllably restricting flow through the valve is a highly polished hard material, preferably synthetic sapphire, having a diameter of 0.062 inch which is larger than the diameter of aperture 17 so that it rests against coined rim 18 of aperture 17 without passing through, thereby forming a seal. The highly polished surfaces of ball 19 and aperture 17 ensure an effective seal when ball 19 is seated, and furthermore, lessen any tendency for the ball to become stuck in the seated position, so enabling a precisely defined and repeatable opening pressure.

Referring now to Fig. 1 and Fig. 4, flat spring 20, having a semicircular bend, is attached to flat plate 14 at 21 by spot welding or other suitable means. The constant of the spring 20 may be varied by altering its width or thickness, thereby allowing for valves with different operating pressures. Spring 20, parallel to the plane of aperture 17, overlies ball 19, touching it at essentially a single point and biasing it against rim 18 8-of aperture 17. This arrangement achieves a narrow hysteresis between opening and closing pressures. When the valve is open, ball 19 is able to spin freely because of the point contact with spring 20, discouraging the accumulation of debris and permitting close regulation of the back pressure presented to the lateral ventricles.

Valve 10 is assembled by inserting the flat piate-ball-spring assembly into valve body 11 from the right side of Fig. 1. The contour of chamber 16 is such that ball 19 will remain within aperture 17 after assembly. This is, shoulder 28 limites the extension of spring 20, thereby assuring that ball 19 cannot become dislodged from aperture 17.

In Fig. 5, the method of testing the sealing characteristics of the shunt valve disclosed herein is illustrated. Light source 25 illuminates one side of flat plate 14 with the ball 1 9 seated. The wavelength of the light from source 25 is selected so that ball 19 is opaque. With a sapphire ball, for example, green light is appropriate. A light detector 26 is arranged on the opposite side of flat plate 14 to detect any light which passes through aperature 17 of flat plate 14. Absence of light reaching the detector indicates a properly sealing valve.

Although in this embodiment injection molded polyethersulfone plastics has been used for valve body 1 1 and stainless steel for flat plate 14 and spring 20, it is obvious that other stable, essentially inert and non-toxic materials could be utilized. Similarly, although synthetic sapphire is the preferred material for ball 19, other hard, nontoxic and inert materials could be substituted.

The disclosed valve is, therefore, compact, light in weight, minimally opaque to X-rays, inexpensive to manufacture and simple to assemble. More importantly, the valve achieves a tight regulation of the cerebrospinal fluid pressure within the cerebra F ventricles, while exhibiting low hysteresis and low susceptibility to clogging with debris enabling it to present a precisely controllable back pressure to the cerebral ventricles.

Claims

1. In a surgically implantable shunt system for venting cerebrospinal fluid from a cerebroventricular catheter to a drainage catheter, a valve for presenting a precisely controllable back pressure to the ventricles, said valve comprising an elongate, hollow valve body, a flat plate partitioning said valve body so as to form an inlet chamber and an outlet chamber, said ventricular catheter being coupled to said inlet chamber and said drainage catheter being coupled to said outlet chamber, said plate being provided with a circular aperture connecting said inlet and outlet chambers, a spherical ball of diameter larger than said aperture for controllably restricting flow through said aperture, and a spring including a cantilevered flat portion overlying said ball and biasing it against the circular periphery of said aperture whereby a circular seal is selectively effected between said ball and said plate, providing a precisely defined back pressure with low hysteresis and low susceptibility to bridging by debris.

2. A shunt system as claimed in Claim 1 in which said flat plate is composed of stainless steel.

3. A shunt system as claimed in Claim 1 or 2 in which said circular aperture presents a highly polished seating for said ball.

4. A shunt system as claimed in Claim 1, 2 or 3 in which the ball is a sapphire ball.

5. A shunt system as claimed in any preceding claim in which said spring is metallic.

6. A shunt system as claimed in any preceding claim in which said cantilevered flat portion of said spring lies parallel to the plane of said aperture when said ball is seated therein.

7. A shunt system as claimed in any preceding claim in which said flat plate is approximately 0.01 inch thick.

8. A shunt system as claimed in any preceding claim in which said circular aperture is approximately 0.057 inch in diameter and ssid ball is approximately 0.062 inch in diameter.

9. A surgically implantable shunt system substantially as hereinbefore described with reference to the accompanying drawings.

10. A method of testing the sealing effectiveness of a valve for presenting a precisely controllable back pressure to the cerebral ventricles, said valve comprising an elongate, hollow valve body, a flat plate partitioning said valve body so as to form an inlet chamber and in outlet chamber, said plate being provided with a circular aperture connecting said inlet and outlet chambers, a spherical ball of diameter larger than said aperture for controllably restricting flow through said aperture, and a spring including a cantilevered flat portion overlying said ball and biasing it against the circular periphery of said aperture, wherein said method comprises directing light energy of a wavelength for which said ball is opaque upon said aperture when said ball is seated against said circular periphery of said aperture, and detecting said light transmitted through said aperture by suitable light detection means, the level of said transmitted light indicating said sealing effectiveness of said valve.

1 1. A valve for presenting a precisely controllable back pressure to the cerebral ventricles in a surgically implantable shunt system for venting cerebrospinal fluid comprising an elongate, hollow valve body, a flat plate partitioning said valve body so as to from an inlet chamber and an outlet chamber, said plate being provided with a circular aperture connecting said inlet and outlet chambers, a spherical ball of diameter larger than said aperture for controllably restricting flow through said aperture, and a spring including a cantilevered flat portion overlying said ball and biasing it against the circular periphery of said aperture.