title: Reliable estimation of nociceptive withdrawal reflex thresholds.
abstract: BACKGROUND
  Assessment of the nociceptive withdrawal reflex (NWR) is frequently applied to probe the excitability level of the spinal nociceptive circuitry. In humans, the NWR threshold (NWR-T) is often estimated by applying electrical stimulation over the sural nerve at the lateral malleolus. Such stimulation may be associated with substantial pain and discomfort rendering completion of the assessment infeasible.
  
  
  METHODS
  As an alternative to sural nerve stimulation, NWR-Ts were also estimated by electrical stimulation at the arch of the foot. Failure-rates and test-retest reliability of these two procedures were evaluated. A fully-automated interleaved up-down staircase procedure was used to estimate the NWR-T for both stimulation sites. NWRs were detected from EMG measured over the biceps femoris and tibialis anterior muscles, respectively. A total of three repeated measures were performed in two different sessions to evaluate the test-retest reliability of the two methods using Bland-Altman agreement analysis.
  
  
  RESULTS
  The failure rate of NWR-T estimation based on electrical stimulation of the sural nerve (29%) was substantially higher than when the NWR was elicited by stimulation at the arch of the foot (5%).
  
  
  CONCLUSIONS
  The analysis of test-retest reliability indicated that the two methods for NWR-T estimation were equally reliable for within-session comparisons, but stimulation at the arch of the foot enabled NWR-T estimation with superior between-session reliability
  
  
  CONCLUSIONS
  These results support a paradigm shift within NWR-T estimation favoring stimulation at the arch of the foot.
authors.affiliation: Center for Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, Room E1-202, 9220 Aalborg Øst, Denmark. Electronic address: mbj@hst.aau.dk.
authors.forename: Michael Brun
authors.initials: MB
authors.lastname: Jensen
authors.affiliation: Center for Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, Room E1-202, 9220 Aalborg Øst, Denmark.
authors.forename: José
authors.initials: J
authors.lastname: Biurrun Manresa
authors.affiliation: Center for Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, Room E1-202, 9220 Aalborg Øst, Denmark.
authors.forename: Ole Kæseler
authors.initials: OK
authors.lastname: Andersen
mesh_terms: D000293:Adolescent; D000328:Adult; D004558:Electric Stimulation / Q000009:adverse effects; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D005528:Foot / Q000294:innervation; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D059225:Nociception / Q000502:physiology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D017603:Signal Detection, Psychological / Q000502:physiology*; D013497:Sural Nerve / Q000502:physiology; D055815:Young Adult
keywords: Nociceptive withdrawal reflex (NWR); Reliability; Spinal nociception