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Identification of Sural Nociceptive flexion reflex Ratio in adult Males 20-40 years of age

Thien Ngo MD PGY – 4 UK PM&R 5/23/2013 Advisors: Drs. Lumy Sawaki & Oscar Ortiz. Identification of Sural Nociceptive flexion reflex Ratio in adult Males 20-40 years of age. Outline. Introduction Objectives Experimental Design Method Results References. Introduction 1.

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Identification of Sural Nociceptive flexion reflex Ratio in adult Males 20-40 years of age

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  1. Thien Ngo MD PGY – 4 UK PM&R 5/23/2013 Advisors: Drs. LumySawaki & Oscar Ortiz Identification of SuralNociceptive flexion reflex Ratio in adult Males 20-40 years of age

  2. Outline • Introduction • Objectives • Experimental Design • Method • Results • References

  3. Introduction 1 • Pain is a subjective experience, and its measurement has been traditionally based on self reported instruments. • Absence of objective instruments • Quantitative sensory testing and nociceptive flexion reflex (NFR) threshold have been explored as options to measure pain more objectively

  4. Introduction 2 • NFR in theory • The NFR is a polysynaptic spinal reflex subserving withdrawal from potentially noxious stimuli. • Provide indirect evidence of supraspinal modulation • The higher the threshold the more inhibition of spinal nociceptive transmission

  5. Introduction 3 • NFR threshold is defined by the lowest noxious stimulation intensity required to trigger a reflex motor response in the biceps femoris muscle.

  6. Introduction 4 Central hyperexcitability as measured with nociceptive flexor reflex threshold in chronic musculoskeletal pain: a systematic review. Lim EC, Sterling M, Stone A, Vicenzino B. Pain. 2011 Aug;152(8):1811-20. Epub 2011 Apr 27

  7. Introduction 5 • Promising results in multiples experimental studies. • Reliable, reproducible, and correlated well with clinical findings within subjects • Significant variability between subjects, despite efforts for standardization, makes it unsuitable for clinical use or establishment of normal values.

  8. Introduction 6 Sural SNAP amplitude using NFRT stimulus NFRI = x 100 Sural SNAP amplitude (supramaximal) • Propose alternative standardized method to measure NFR that avoid variability (mostly due to changes in skin resistance).

  9. Objectives • The goal of this pilot study is to begin to establish normative data of NFRI in young male adults. Our proposed study has 2 specific aims: • Specific Aim #1:Identify the “normal” suralnociceptive flexion reflex threshold (NRFT) and the suralnociceptive flexion reflex ratio (NFRR) in male adults of 20 to 40 years of age. • Specific Aim #2:Measure the correlation between the NFRI and level of pain as measured by Visual Analogue Scale (VAS).

  10. Experimental Design • Recruitment: Flyers and volunteer subjects • Screening process and informed consent • Inclusion Criteria: • Healthy male 20-40 • Exclusion Criteria: • Avoiding confounding factors of NFR and NFRT recording • Head injury, alcohol/drug abuse, psychiatric illness, on psychiatric/pain medications, neurological disorder, chronic pain, h/o cancer, and peripheral neuropathy

  11. Method (Step 1) (Sural sensory nerve action potential)

  12. EMG Machine

  13. Method (Step 2) (Nociceptive Flexion Reflex)

  14. EMG machine - Biceps Femoris Reflex

  15. Graph 1: Subject by Subject Responses: biceps reflex, pain index, and NFRR Graph 1. Pain index and NFRR showed a closed correlation with subject 1, 2, 4, 6, & 7. There was no significant correlation between pain and biceps reflex intensity.

  16. Graph 2: Correlation between pain index vs biceps reflex Graph 2. Biceps Reflex (mA) vs Pain Index showed 59% correlation

  17. Graph 3: Pain index vs NFRR Graph 3. Lack of a correlation between pain index and NFRR

  18. Conclusion/Discussion: • No significant findings • Variability • Take away points • Revise gold standard • Minimal threshold for SNAP • Standard stimulus for pain index

  19. References • 1.) Giorgio, S. et al. “The lower limb flexion reflex in humans”. (2005) Progress in Neurobiology 77: 353-395. • 2.) Rhudy, J. & France, C. “Defining the nociceptive flexion reflex (NFR) threshold in human participants: A comparison of different scoring criteria”. (2007) Pain 128: 244-253. • 3.) France, C. et al. “Using normalized EMG to define the nociceptive flexion reflex (NFR) threshold: Further evaluation of standardized NFR scoring criteria”. (2009) Pain 145: 211-218. • 4.) Terry, E. et al. “Standardizing procedures to study sensitization of human spinal nociceptiveprocesses: Comparing parameters for temporal summation of the nociceptiveflexionreflex (TS-NFR)”. (2011) International Journal of Psychophysiology 81: 263-274. • 5.) Micalos, P. et al. “Reliability of the nociceptive flexor reflex (RIII) threshold and association with Pain threshold”. (2009) Eur J ApplPhysio 105: 55-62.

  20. Thank you!

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