1. Field of the Invention
The present invention relates to a valve for the treatment of hydrocephalus.
It is known that hydrocephalous is a disease caused notably by an abnormal accumulation of cephalo-rachidian or cerebrospinal fluid in the cavities (ventricles) of the brain, and more particularly by the clogging of the natural loculi (usually referred to as arachnoid villosities) for the resorption of the cephalo-rachidian fluid. This clogging is attended by a volumetric increment of the ventricles of the cranial cavity of brain-pan and consequently of the skull itself in newborn children having still open fontanelles.
In adults, due to the rigidity of the brain-pan, this disease is revealed by disorders affecting the locomotive organs, by incontinences, mental disorders and/or a gradual deterioration of the cerabral parenchyma.
One known method of treating this disease consists in diverting the cephalo-rachidian fluid contained in the ventricles of the cranial cavity towards any other resorption region such as the heart or the peritoneum.
For this purpose, a catheter is introduced into one of the ventricles of the brain-pan by trepanning the patient's skull, this catheter being subsequently connected to another tube inserted under the scalp and leading at the neck level either to the jugular vein (in which case the apparatus is completed by introducing a distal catheter into the left-hand auricle) or simply to the peritoneum.
Therefore, the assembly comprises an upstream catheter and a downstream catheter, but in fact it constitutes a unitary system which must be connected once or twice, according to the particular model utilized. The shunt assembly, from its proximal end to its distal end, is completely sub-cutaneous, thus affording a certain freedoom of movement to the patient and avoiding infections.
The arachnoid villosities keep a constant pressure between the cephalo-rachidian fluid and the venous blood. Furthermore, they prevent the ventricles of the brain-pan from being drained off in the orthostatic position.
Consequently, when a system for diverting the cephalo-rachidian or cerebro-spinal fluid is grafted to a patient, an adequate valve system must be inserted therein.
This valve is disposed either at the end of the system and is therefore a distal valve disposed near the trepan orifice, and in this case the valve is referred to as a proximal one.
2. The Prior Art
A number of valve types have already been proposed up to now for such shunting systems utilized in the treatment of hydrocephalus.
Among these known valves, those invented by Pudenz, Raimondi and Holter are of the slotted type and are simply formed in the wall of the tube consisting of silicone elastomer, the valve slots opening when the cephalo-rachidian fluid attains a predetermined pressure.
The Pudenz and Raimondi valves comprise slots formed at the distal, closed end of the circuit.
The Holter valve comprises a tubular sheath adapted to be positionned in the vicinity of the trepan orifice. In the sheath ends small cupula of a silicone base material are introduced and have lateral slots formed therein to permit the flow of cephalo-rachidian fluid therethrough.
Also known in the art is the Hakim valve which comprises a mechanical device for controlling the fluid pressure.
This device consists of a ball valve cooperating with a frustoconical seat; this ball valve is urged to its seated position by a gaged spring so that the valve will open under a predetermined pressure. One advantage of this Hakim valve over slotted valves is that it opens under a precision-gaged pressure.
However, whatever the precision of operation of these known valves, they are objectionable in that they are capable of operating in only one pressure range, so that a complete series of valves must be provided for operating in different pressure ranges consistent with the various cases of hydrocephalus to be treated.
Moreover, it may be expected that during the evolution of the disease or during its treatment the valve ingrafted initially will open under an excessive high or low pressure.
In this case the valve must be replaced and this involves of course another surgical operation.