System for controlling an implanted neural stimulator

• US 4,735,204 A
• Filed: 10/30/1986
• Issued: 04/05/1988
• Est. Priority Date: 09/17/1984
• Status: Expired due to Term

• Current Assignee: Cordis Corporation (Cardinal Health, Inc.)
• Original Assignee: Cordis Corporation (Cardinal Health, Inc.)
• Inventors: Yomtov, Barry M., Sussman, Marvin L.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/924,743
• Time in Patent Office: 523 Days
• Field of Search: 128/419 C, 128/419 E, 128/419 P, 128/419 PG, 128/419 R, 128/421, 128/422, 128/423 R
• US Class Current: 607/60
• CPC Class Codes: A61N 1/37217 characterised by the communication link, e.g. acoustic or tactile

Abstract

An improved control system for a neural stimulator allowing either the patient or physician to effect the level of output by application of an external magnet. Such application of a magnet for a predetermined period of time initiates an incrementally increasing output, under control of an implanted microprocessor, allowing human feedback from the patient to determine the effective level of output current to fix the output at the selected effective level.

Claims

1. A neural stimulating system for permitting patient control of a neural stimulator within preset limits in response to an externally and manually applied magnetic field, said neural stimulating system comprising:

a magnet for use by the patient;

a magnetically controlled switch for implantation in a patient'"'"'s body just beneath the patient'"'"'s skin and for being positioned at a location in the body for selective closing by application of an external magnetic field as established by placing said magnet over the patient'"'"'s skin adjacent said switch;

a neural stimulating electrode for implantation in a patient'"'"'s spine adjacent the patient'"'"'s spinal cord; and

a neural stimulator including programmable electronic circuit means for implantation in a patient'"'"'s body, such as adjacent said switch, said circuit means being electrically coupled to said magnetically controlled switch and to said neural stimulating electrode and said circuit means including means for generating a selective electrical output current between a minimum level of zero current, programmed into said circuit means and a maximum level programmed by a physician into said circuit means in response to closing of and duration of the closure of said magnetically controlled switch, which output current is supplied to said neural stimulating electrode,

said means for generating an output current including means for generating gradually, incrementally increasing neural stimulating electrical output current pulses, in response to the application of the externally applied magnetic field to said magnetically controlled switch for a predetermined period of time.

2. The system of claim 1 wherein said means for generating gradually, incrementally increasing neural stimulating electrical output current pulses includes means for generating current pulses along a ramp function.

3. The system of claim 1 wherein said electronic circuit means comprises means for detecting the electrical output current being generated at the time of removal of the externally applied magnetic field and the opening of said magnetic actuated switch and for maintaining said output current at the detected level.

4. The system of claim 3 wherein said implanted circuit means comprises a microprocessor coupled to said switch and to said current generating means.

5. The system of claim 4 wherein said microprocessor includes means for detecting the opening and closing of the magnetically actuated switch and means for turning the neural stimulator or in response to closure of said switch for a first duration, means for turning the neural stimulator off in response to a closure of said switch for a second duration following immediately after said first duration, and means for initiating an incrementally increasing neural stimulator output current in response to a closure of said switch for a third duration following immediately after said second duration.

6. A method for controlling, by a patient, the operation of a neural stimulating system including a magnet, a neural stimulator implanted in a patient'"'"'s spine including current generating means, a microprocessor implanted beneath a patient'"'"'s skin coupled to said current generating means and a magnetically responsive reed switch means implanted beneath a patient'"'"'s skin and connected to the microprocessor, said method comprising the steps of:

manually causing, from a position exterior of a patient'"'"'s body, closing of the reed switch means for a predetermined time period by holding the magnet adjacent said reed switch means for said predetermined time period;

generating output current pulses from the neural stimulator;

and

causing the output current pulses from the neural stimulator to increase incrementally from a minimum value of 0 so long as the reed switch means is closed beyond the predetermined time period and only until a certain current level is reached which is the lesser of a level of output current that interrupts human body generated pain pulses and a maximum output current level of the neural stimulator preprogrammed by a physician into the microprocessor;

said step of causing the output current pulses to increase including the step of utilizing means for gradually and incrementally increasing the output current pulses to increase the output current pulses incrementally to successively higher current values.

7. The method according to claim 6 wherein said predetermined time period is at least 6 seconds.

8. The method of claim 6 wherein said step of incrementing the output current pulses is carried out over a time period of a ramp function for current values from 0 milliamps to a maximum of 8.9 milliamps.

9. The method of claim 6 wherein said step of incrementing the output current pulses is carried out according to a ramp function which is started at a time approximately 6 seconds after initial closing of the switch means and is continued for a duration of 30 seconds for a total switch means closed period of 36 seconds.

10. The method of claim 6 wherein said step of causing the output current pulses from the neural stimulator to increase includes the step of gradually and incrementally increasing the output current pulses along the slope of a ramp function from 0 to said maximum programmed output current level.

11. The method of claim 10 wherein said step of incrementally increasing the output current pulses includes incrementally increasing the output current in steps of 0.12 milliamps per step along the ramp function.

12. The method of claim 10 wherein said ramp function has a duration of 30 seconds.

13. The method of claim 10 wherein said output current increases over the timer period of said ramp function from 0 milliamps to a maximum of 8.9 milliamps.

14. The method of claim 6 wherein said step of incrementing the output current pulses in steps includes generating 3 bursts of output current pulses at one level followed by 3 bursts of current pulses at a next succeeding level approximately 0.12 milliamps above the preceding level.

15. The method of claim 14 where the step of generating 3 current pulses includes generating said current pulses over a time period of 0.024 seconds for each step increase in current.

16. The method of claim 10 wherein said step of incrementally increasing the output current pulses includes increasing the output current pulses over a time period of said ramp function from 0 milliamps to a maximum of 8.9 milliamps.

17. The method of claim 6 wherein said step of closing the switch means for a time period of more than 2 seconds and less than 6 seconds includes turning off the neural stimulator.