Quantitative SSEP and EEG as Objective Pain Biomarker

Over the past few years, significant advances have begun to be made in the development of
particular measures as valid biomarkers or surrogate markers for the presence of acute and/or
chronic pain. Many of these advances have been made because of the development of new and
improved technologies, for example in the fields of imaging and genetics. Research is now
showing brain activity and brain organizational changes associated with the presence of pain.
Various factors have been found in the blood that is associated with the presence of pain.
Research is also suggesting that pupil responses to a variety of stimuli may predict the
presence of pain and machine learning analysis of videos has found facial movement patterns
in both animals and humans that are correlated with the presence of pain.

The establishment of a biomarker of pain is a key requirement for understanding the
person-specific effects of anesthetic and analgesic drugs. An objective pain measure will be
an integral part in the planning of an anesthetic and potentially enable the researchers to
answer the question whether proper matching of the anesthetic or analgesic dose to a person's
individual profile will result in better cognitive recovery from anesthesia.

There are several approaches to quantifying pain in an objective fashion. These approaches
are based on the observation of afferent signals to the brain, brain integration of
nociceptive signals or secondary responses to nociceptive signals (ocular, facial, autonomic
or behavioral responses). Pain has been studied extensively with fMRI. Several other methods
have been proposed: pain behavior, pupillary responses, and autonomic responses.

Somatosensory evoked electrical potentials (SSEP) are routinely recorded to assess the
integrity of sensory pathways during spine surgery. Our primary study aim is to correlate the
neuronal (EEG) signal (Y1) and/or γ - band power (Y2) with both the stimulus intensity (X1,
the voltage of constant current stimulator output) and the perceived pain intensity (X2)

This is a pilot study to test the hypothesis that the gamma frequency range (30 -100 Hz) of
standard EEG or somatosensory evoked potential (SSEP) correlate with intensity of an
experimental pain stimulus and perceived (self-rating, subjective) pain intensity.

Inclusion Criteria:

- Adult human volunteers (age > 18) that are able to understand study procedures.

Exclusion Criteria:

- Medical conditions that would interfere with somatosensory processing. (diabetic
neuropathy, stroke), chronic pain, medications known to affect pain processing (opioid
therapy, selective serotonin reuptake inhibitor (SSRI)).