Electrophysiological Tests Used in the Evaluation of Peripheral Neuropathy and Neuropathic Pain - PowerPoint PPT Presentation

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Electrophysiological Tests Used in the Evaluation of Peripheral Neuropathy and Neuropathic Pain

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Title: Electrophysiological Tests Used in the Evaluation of Peripheral Neuropathy and Neuropathic Pain


1
Electrophysiological Tests Used in the Evaluation
of Peripheral Neuropathy and Neuropathic Pain
  • David R. Cornblath, MD
  • Johns Hopkins

2
Outline
  • Electrophysiological Tests
  • Natural History in Diabetes
  • Correlation with Outcomes
  • Use in Clinical Trials
  • Practical Issues
  • Summary

3
Neurophysiological Tests
  • Nerve conductions sensory and motor and F waves
  • Electromyography
  • Quantitative sensory testing
  • Autonomic function testing
  • QSART

4
Natural History of EDx Studies in Diabetes
  • Most comprehensive data is the RDNS which shows a
    gradual worsening in neuropathy over time -0.34
    NIS(LL)7 points/year in diabetes and -0.85
    NIS(LL)7 points/year in DPN.
  • Depending on the treatment study examined, the
    data vary somewhat but all show worsening over
    time.

5
Correlation of Edx Tests with Outcomes
  • The best data comes from Dr. Dyck and colleagues
    who suggest that a clinically detectable and
    meaningful change in neuropathy is a 2 point
    change in NIS which is equal to a 2.9 m/s or 1.2
    mV change for avg. of median, ulnar and peroneal
    nerves or 2.2 m/s or 0.7 mV change for peroneal
    nerve alone.

6
EDx Tests in Clinical Trials
  • Frequently used in neuropathy clinical trials as
    either primary or secondary endpoint.
  • NCS show improvement when the change in diabetes
    is dramatic such as with transplantation,
    intensive control, or in children.
  • NCS have not shown improvement in most clinical
    trials, but that may be a related to the lack of
    therapeutic successes or the parameter chosen.

7
Practical Issues
  • What is the desired outcome?
  • Which fiber population will be affected?
  • What parameter of NCS will be affected?
  • How fast will intervention work?
  • Which test to use?
  • What is hypothesized to occur from the
    intervention?
  • Can this be done in multiple sites given the need
    for standardization, reproducibility, and
    reliability?
  • Yes for NCS (see recent multi-center Japanese
    data)

8
Summary
  • Peripheral Neuropathy
  • Of the many tests, nerve conductions are the best
    studied and most accepted tests and correlate
    with clinical measures. A change over time is
    real. NCS can detect improvement or worsening.
  • The other electrophysiological tests may be used
    in selected cases, but more data is needed on
    many of the practical issues.
  • Nerve conductions are useful as part of composite
    measures of neuropathy such as NIS(LL)7 and TNS.

9
Summary
  • Neuropathic Pain
  • Electrophysiological tests are valuable as a
    monitoring tool for toxicity.
  • Nerve conductions should not be used as outcome
    criteria as they measure large fiber function,
    not small fiber function.
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