Method and apparatus for intracranial pressure estimation

• US 4,564,022 A
• Filed: 03/12/1982
• Issued: 01/14/1986
• Est. Priority Date: 03/12/1982
• Status: Expired due to Fees

• Current Assignee: Clark Watts, Donald H. York, John G. Rosenfeld
• Original Assignee: Clark Watts, Donald H. York, John G. Rosenfeld
• Inventors: York, Donald H., Rosenfeld, John G., Watts, Clark
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US06/357,482
• Time in Patent Office: 1,404 Days
• Field of Search: 128/748, 128/731-732
• US Class Current: 600/561
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 5/377 using evoked responses

Abstract

A method and apparatus for non-invasively estimating the intracranial pressures of a subject is provided. A sensory stimulus is directed towards the subject thereby generating electrical brain activity. A peak in the second negative-going wave of the brain activity is identified and the latency of such peak is measured. The intracranial pressure of the subject is estimated by comparing value of the latency with known latency/intracranial pressure correlations.

Claims

1. A method for estimating intracranial pressure comprising the steps of:

(a) generating at least one evoked potential;

(b) measuring the value of the latency of a peak of said evoked potential; and

(c) comparing the value of said latency with known latency/intracranial pressure correlations to determine an estimated intracranial pressure.

2. The method of claim 1 wherein a plurality of evoked potentials are generated and an average peak latency is determined.

3. The method of claim 1 wherein said peak is the second negative-going peak of said at least one evoked potential.

4. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) attaching an electrode to the subject'"'"'s head to measure potentials;

(b) providing a sensory stimulus to the subject to produce an evoked potential;

(c) measuring the interval between said sensory stimulus and a peak voltage potential on said electrode; and

(d) identifying an estimated range of intracranial pressure corresponding to said measured interval.

5. The method of claim 4 wherein said interval is in the range of approximately 60 to 108 milliseconds.

6. The method of claim 4 wherein a first electrode is placed on the subject'"'"'s skull vertex, a second electrode is placed on the subject'"'"'s left earlobe, and a third electrode is placed on the subject'"'"'s right earlobe, and said peak voltage potential is a differential voltage between said first electrode and said second and third electrodes.

7. The method of claim 4 wherein said peak voltage potential is the second negative-going peak of said voltage potential.

8. A method for estimating the intracranial pressure of a subject comprising the steps of:

(a) evoking a potential by means of a sensory stimulus;

(b) recording the values of a plurality of discrete points along said potential in the time range of approximately 60 to 108 milliseconds after said stimulus;

(c) analyzing said values to determine the location of a change in slope from negative to positive along said potential in said time range; and

(c) calculating a range of estimated intracranial pressure corresponding to said location of said change in slope.

9. The method of claim 8 further comprising the step of reiterating said step of evoking a potential a predetermined number of times.

10. The method of claim 9 further comprising the step of averaging said recorded discrete point values.

11. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure;

(f) wherein said analog response is sampled at a plurality of intervals such that a plurality of discrete digital values are generated which represent said analog response; and

(g) wherein said discrete digital values are generated within the time interval of approximately 60 to 108 milliseconds after each stimulus.

12. A method of estimating the intracranial pressure of the subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure; and

(f) wherein said output signal indicates a range of estimated intracranial pressure.

13. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure;

(f) wherein said analog response is sampled at a plurality of intervals such that a plurality of discrete digital values are generated which represent said analog response;

(g) wherein said discrete digital values are each stored in a unique memory location;

(h) wherein a plurality of stimuli are provided and said discrete digital values corresponding to each said interval are summed; and

(i) monitoring said discrete digital values for an out-of-range condition and providing one additional stimulus when an out-of-range condition is sensed.

14. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure; and

(f) eliminating abnormal fluctuations in said analog response by means of a curve smoothing routine.

15. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure; and

(f) wherein said step of determining a peak location determines a peak in the second negative-going wave of said analog response.

16. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure;

(f) wherein said analog response is sampled at a plurality of intervals such that a plurality of discrete digital values are generated which represent said analog response; and

(g) wherein said step determining a peak location comprises analyzing said discrete digital values for a change in slope from negative to positive.

17. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure; and

(f) generating an error signal if no said peak location is determined in said step of determining a peak location.

18. A method of estimating the intracranial pressure of a subject comprising the steps of:

(a) providing at least one sensory stimulus to the subject;

(b) sensing an analog electrical brain response of the subject to said at least one stimulus by means of an electrode;

(c) converting said analog response to a digital signal;

(d) determining a peak location in said digital signal by means for digital computing;

(e) generating an output signal representative of said peak location to indicate estimated intracranial pressure; and

(f) generating an error signal if more than one peak location is determined in said step of determining a peak location.

19. An apparatus for estimating intracranial pressure of a subject comprising:

(a) means for generating a potential evoked by a sensory stimulus;

(b) means for measuring the value of the latency of a peak of said potential; and

(c) means for comparing the value of said latency with known latency/intracranial pressure correlations to determine an estimated intracranial pressure.

20. An apparatus for estimating intracranial pressure of a subject comprising:

(a) an electrode adapted to be attached to the head of the subject to measure voltage potentials;

(b) means for providing a sensory stimulus to the subject;

(c) means for measuring the interval between said stimulus and a peak voltage potential on said electrode; and

(d) means for identifying an estimated range of intracranial pressure corresponding to said measured interval.

21. An apparatus for estimating intracranial pressure of the subject comprising:

(a) a source of light disposed to be viewed by the subject;

(b) an electrode adapted to be attached to the subject'"'"'s head to detect the subject'"'"'s electrical brain activity;

(c) means for causing said source of light to flash, thereby stimulating electrical brain activity of the subject;

(d) computer means for detecting a latency of a peak in said electrical brain activity with respect to said flash of said source of light; and

(e) output means for indicating a range of intracranial pressure determined with respect to said detected peak latency.

22. The apparatus of claim 21 further comprising storage media means for recording signals indicative of said electrical brain activity stimulated by said source of light.

23. The apparatus according to claim 22 further comprising microprocessor means for controlling said means for causing said light to flash, said storage media, and said output device.