Electrode insertion tool

Details Electrode insertion tool Electrode insertion tool

1999-10-27

2001-10-16

Schaetzle, Kennedy (Department: 3762)

Surgery: light, thermal, and electrical application

Light, thermal, and electrical application

Electrical energy applicator

C607S117000, C607S137000, C600S377000, C128S899000, C606S129000

Reexamination Certificate

active

06304785

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a simple and reliable mechanical tool for inserting medical electrodes into nerve tissue such as the cerebral cortex, brain stem and the spinal cord. The tool can be hand held, or mounted in a stereotactic positioning device. An alternative embodiment of the tool uses a curved tip for holding the electrode for insertion in the cochlear nucleus of the brain as part of a procedure to assist a profoundly deaf patient.
The tool is especially useful with small medical electrodes having a button-like cylindrical base, typically made of epoxy, of about 2.5-mm diameter and about 0.5-mm thickness. Typically, multiple (e.g., seven) relatively sharp time-like electrodes (the length depending on the application, but typically in the range of 1 to 6 mm) extend from the base, and connecting leads enable individual or parallel energization of the electrodes depending on the nerve-stimulation protocol being used.
The challenge met by the invention is to move the positioned electrode with an initially high acceleration to enable the electrode times to penetrate at high velocity the tough and puncture-resistant pia-arachnoid member overlapping the cortex and spinal cord. It is then desirable to stabilize and cease accelerating the penetration rate to prevent injury to the underlying neuron al population, and to the delicate arterial and venous blood vessels.
An important advantage of the invention is that the electrodes and associated base are recessed within a tip of the insertion tool prior to actuation. This feature enables the tool tip to be positioned against the tissue to be penetrated, thus enabling handheld operation as opposed to the sometimes cumbersome mounting of the tool in a stereotactic positioning device.
Several alternative velocity-control mechanisms are disclosed which approximate viscous damping of movement of the electrode driving mechanism to enable high initial acceleration until penetration is achieved, with controlled and relatively stabilized velocity thereafter.
SUMMARY OF THE INVENTION
The electrode insertion tool of this invention includes a tubular handle having a reduced-diameter tubular tip. A guide wire extends through the handle and into the tip to be secured to an injection piston slidably moveable within the tip. An electrode assembly can be fully inserted against the injection piston to be shrouded by the tip, thus enabling the tip to be placed directly against the tissue into which the electrode assembly is to be inserted.
A compression spring is positioned within the handle, and is compressed between an adjustable normally stationary plug and a moveable ring which is secured to the guide wire. A cocking knob extends from a rear end of the handle and is secured to the guide wire so the knob can be retracted to move the ring toward the stationary plug to compress the spring. An external trigger on the handle holds the plug in the spring-compressed “cocked” position, and the trigger is moveable to release the plug and “fire” the tool to move the electrode assembly forwardly out of the tubular tip.
To provide a high initial acceleration of the guide wire and electrode assembly, followed by a relatively constant velocity (typically in the range of one-to-four meters per second), a means is provided within the handle to provide motion control approximating viscous damping, and restraining force approximately proportional to velocity of the moving system, thus enabling high initial acceleration. The damping means is described in terms of both magnetic eddy-current braking force, and piston-cylinder drag force.


REFERENCES:
patent: 5306251 (1994-04-01), Alexander
patent: 5361760 (1994-11-01), Normann et al.
patent: 5443493 (1995-08-01), Byers et al.
patent: 6056716 (2000-05-01), D'Antonio et al.
Annals of Biomedical Engineering (1992) pp. 413-422.
A Microassembly Structure for Intracortical Three-Dimensional Electrode Arrays (1996) five pages.

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