RELIABLE ASSESSMENT OF THE HUMAN NOCICEPTIVE WITHDRAWAL REFLEX AND REFLEX RECEPTIVE FIELDS: INTRODUCTION OF NEW METHODS

The nociceptive withdrawal reflex (NWR) is considered a reliable and objective tool in pain assessment. It is often assessed by estimation of a single NWR threshold (NWR-T) but spatial assessment is possible by quantification of the reflex receptive field (RRF). Both methods are sufficiently sensitive to detect abnormal spinal nociception in groups of pain patients but large interpersonal variance limits their clinical use. Variability comprises personal differences but may be exacerbated by the use of non-optimal assessment methodologies.

In this Ph.D. project specific imperfections of existing methods were addressed to enable more valid and reliable assessment of NWRs and RRFs.

NWR detection from standard electromyography (EMG) is extremely sensitive to EMG crosstalk and a method to handle this type of noise, based on analysis of muscle fiber conduction velocity was developed. Conventional NWR-T estimation was found associated with a high failure rate but a change of stimulation site yielded a reduced failure rate and superior reliability. Finally, a completely objective methodology was developed to enable more reliable RRF quantification.

This work suggests that limited reliability of existing methods may contribute to the large variability observed and that the introduced initiatives can be applied to enable more reliable assessment of NWRs and RRFs.