Abstract: An apparatus and method of making a hole of a first predetermined diameter in a dura of a patient for the insertion of a catheter having a second predetermined diameter. A burr hole is created in the cranium of the patient, if necessary. A stylet is inserted into the lumen of a catheter with an end of the stylet formed with a tip having a diameter having a predetermined relationship with the first predetermined diameter such that the distal end of the stylet is proximate to a distal end of the catheter. The end of the catheter is inserted into the burr hole of the cranium. An electrical current is applied to the stylet in order to cauterize the dura creating a hole in the dura approximately equal to the diameter of the tip.

Abstract: An apparatus and method of making a hole of a first predetermined diameter in a dura of a patient for the insertion of a catheter having a second predetermined diameter. A burr hole is created in the cranium of the patient, if necessary. A stylet is inserted into the lumen of a catheter with an end of the stylet formed with a tip having a diameter having a predetermined relationship with the first predetermined diameter such that the distal end of the stylet is proximate to a distal end of the catheter. The end of the catheter is inserted into the burr hole of the cranium. An electrical current is applied to the stylet in order to cauterize the dura creating a hole in the dura approximately equal to the diameter of the tip.

Abstract: A method of making a spring are described. The spring is made by etching or cutting at least one spiral arm in a flat substrate leaving residual material around the arm. The intermediate residual material is either pushed or lifted to form a conical spring.

Abstract: A valve seat for a ball valve in an adjustable medical valve is described. The valve seat is formed as a cone in a manifold. The cone is formed by rotating a line that intersects a central axis of the valve seat around the central axis. The angle of the intersection between the line and the central axis is doubled to form the included angle of the valve seat. Generally, the narrower the included angle, the better the tolerance of the assembled valve for variations in the spring constant of the pressure regulating spring. Specifically, the present invention has included angles between 0 and 90 degrees with the preferred included angles being between 10 and 40 degrees. A valve embodying the valve seat is also disclosed.