METHOD AND SYSTEM FOR MONITORING A NERVE

• US 20150320329A1
• Filed: 07/20/2015
• Published: 11/12/2015
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Medtronic Xomed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Xomed Incorporated (Medtronic Plc)
• Inventors: Brunnett, William C., Hacker, David C., Meyer, John A., McFarlin, Kevin Lee, Murphy, John Murdock, Yamasaki, Dwayne S., Gardi, John N.
• Granted Patent: US 9,579,037 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2505/05 Surgical care
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition
• CPC Class Codes: A61B 5/4893 Nerves
• CPC Class Codes: A61B 5/6877 Nerve
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/741 using synthesised speech
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61N 1/0556 Cuff electrodes
• CPC Class Codes: A61N 1/3605 Implantable neurostimulators for stimulating central or peripheral nerve system

Abstract

A nerve monitoring system facilitates monitoring an integrity of a nerve.

Claims

1. A system for monitoring a nerve, the system comprising:

a monitor including;

a stimulation module configured to automatically and periodically apply an electrical stimulation signal to the nerve to elicit an evoked potential; and

a response module configured to automatically measure a neurogenic response signal of the evoked potential, the response module including;

an identification function configured to automatically identify potential nerve impairment based on the measured neurogenic response signal; and

a notify function configured to automatically provide an audible or visual alarm of the potential nerve impairment.

2. The system of claim 1, wherein the measured neurogenic response signal comprises at least one of:

a direct response signal measured at a location of the nerve spaced apart from a location at which the stimulation signal is applied;

an indirect response signal measured at a muscle innervated by the nerve;

a chemical-based neurogenic response signal;

or

a smooth muscle-based neurogenic response signal.

3. The system of claim 1, wherein the identification function is configured to automatically identify the potential nerve impairment based on differences between the measure neurogenic response signal and a baseline neurogenic response pattern and wherein the notify function is configured to automatically provide one of the respective alarms when the differences exceed a predetermined limit.

4. The system of claim 3 wherein, in cooperation with the identification function, the response module comprises at least one of:

an amplitude function to identify a decrease in the amplitude of the measured response signal relative to an amplitude parameter of the baseline response pattern;

a latency function to identify an increase in the latency of the measured response signal relative to a latency parameter of the baseline response pattern;

or

an amplitude-based energy function to identify a decrease in an energy of the measured response signal relative to an energy parameter of the baseline response pattern.

5. The system of claim 3 wherein, in cooperation with the identification function, the response module comprises at least one of:

a nerve conduction velocity function configured to identify an increase or decrease in a nerve conduction velocity of the measured response signal relative to a nerve conduction velocity parameter of the baseline response pattern;

a first nerve refractory recovery function configured to identify, relative to a nerve refractory recovery parameter of the baseline response pattern, a change in at least one of a double response time, an amplitude, or a latency of a nerve refractory recovery waveform produced in response to a plurality of the stimulation signals;

or

a second nerve refractory recovery function configured to identify, relative to a nerve refractory recovery parameter of the baseline response pattern, a change in at least one of a neurogenic response morphology waveform or a neurogenic response synchrony pattern produced in response to a plurality of the stimulation signals.

6. The system of claim 3 wherein, in cooperation with the identification function, the response module comprises at least one of:

a nerve stimulation threshold function to identify an increase or decrease a nerve stimulation of the measured response signal relative to a nerve stimulation parameter of the baseline response pattern;

or

a nerve stimulation saturation function to identify an increase or decrease a nerve stimulation saturation of the measured response signal relative to a nerve stimulation saturation parameter of the baseline response pattern.

7. The system of claim 3, wherein the response module determines the baseline response pattern as an identification of an initial neurogenic status of the nerve according to multiple evoked responses via at least one of:

a statistical mean of the multiple evoked responses;

or

a variance measurement of the multiple evoked responses.

8. The system of claim 3, wherein the response module determines the baseline response pattern as an identification of an initial neurogenic status of the nerve via sorting a variability of the multiple evoked responses according to a Poisson distribution.

9. The system of claim 3, wherein the response module determines the baseline response pattern as an identification of an initial neurogenic status of the nerve according to multiple evoked responses via at least one of:

an exclusion of a portion of the multiple evoked responses based on a variability of the multiple evoked responses;

an exclusion of at least one of a maximum value or a minimum value of the multiple evoked responses;

or

an exclusion of non-evoked responses.

10. The system of claim 3, wherein the response module determines the baseline response pattern as an identification of an initial neurogenic status of the nerve according to multiple evoked responses via at least one of:

a rate of change of at least one parameter of the multiple evoked responses;

or

a rolling window of multiple evoked responses.

11. The system of claim 3 wherein the system includes a user interface configured to communicate the visual alarm or the audible alarm of the notify function and wherein the notify function includes at least one of:

a graduated type of notification in which a volume of the alarm is in proportion to a degree of deviation of the measured response from the baseline response pattern;

or

a tone type of notification in which a type of tone corresponds to a degree of deviation of the measured response from the baseline response pattern.

12. The system of claim 1 wherein the system includes a user interface configured to communicate the visual alarm or the audible alarm of the notify function and wherein the notify function includes a verbal function configured to audibly announce one or more verbal expressions that communicate at least one of a type of impairment to the monitored nerve and a degree of impairment to the monitored nerve.

13. The system of claim 1, comprising:

a cuff electrode removably securable to the nerve to maintain a continuous electrical pathway from the stimulation module to the nerve throughout the surgical procedure.

14. The system of claim 1, comprising:

a response electrode removably securable relative to at least one of the nerve or an innervated muscle to maintain a continuous electrical pathway from the respective nerve or the innervated muscle to the response module throughout the surgical procedure.

15. The system of claim 1 wherein the response module comprises an impairment sorter including an assessment module configured to assess a type, and a degree of, impairment to the monitored nerve.

16. The system of claim 15 wherein the assessment module includes a differentiator module configured to classify the type of impairment as at least one of:

a minor tension impairment of the nerve as indicated by an increase in response latency and an increase in response amplitude;

a tension impairment of the nerve as indicated by an increase in response latency and a decrease in response amplitude;

a compression impairment of the nerve as indicated by a decrease in response amplitude without a substantial change in latency;

a composite impairment of the nerve including at least two of the types of the minor tension impairment, the tension impairment, or the compression impairment;

or

an electrocautery impairment of the nerve as indicated by a detected electrocautery event occurring substantially synchronous with at least one of the types of the minor tension impairment, the tension impairment, the compression impairment, or the composite impairment.

17. The system of claim 15 wherein the impairment sorter comprises:

a reporting module configured to audibly announce one or more verbal expressions to report the type of impairment to the nerve and to report an intensity of the impairment.

18. A method of monitoring impairment of a nerve during a surgical procedure, the method comprising:

automatically identifying, via a hands-free mechanism, a type and an intensity of impairment of the nerve; and

automatically providing notification of the type or the intensity of the impairment to the nerve.

19. The method of claim 18 wherein automatically identifying the type and intensity of the impairment includes:

measuring a neurogenic response signal upon application of a stimulation signal to the nerve and identifying the potential impairment of the nerve, without regard to a baseline response signal, based on at least one of an amplitude, a latency, a waveform morphology, or a synchrony pattern of the measured neurogenic response signal.

20. The method of claim 18 wherein measuring a neurogenic response comprises:

providing at least a portion of the hands-free mechanism via removably securing a cuff electrode about the nerve to continuously maintain an electrical pathway from a monitor to the nerve during a surgical procedure performed in the vicinity of the nerve; and

performing a surgical procedure adjacent to the nerve while automatically applying the stimulation signal at periodic intervals to the nerve via the cuff electrode.