Secondary hyperalgesia phenotypes exhibit differences in brain activation during noxious stimulation.

Area of Science:

• Neuroscience
• Pain Research
• Medical Imaging

Background:

• Noxious stimuli cause primary and secondary hyperalgesia.
• Secondary hyperalgesia results from central neuronal sensitization.
• Individuals vary in secondary hyperalgesia extent, termed high- or low-sensitization responders, a reproducible phenotype.

Purpose of the Study:

• To investigate brain activity and anatomical differences between high- and low-sensitization responders.
• To explore the relationship between secondary hyperalgesia phenotype and central sensitization.

Main Methods:

• Magnetic resonance imaging (MRI) was used to assess brain structure and activity.
• Forty healthy volunteers received a standardized burn injury.
• Blood-oxygen-level-dependent (BOLD) signals measured neuronal activation during noxious stimulation.
• T1-weighted images assessed gray-matter density.

Main Results:

• Significant differences in baseline and post-injury neuronal activity were observed between high- and low-sensitization responders.
• High-sensitization responders showed decreased gray-matter volume in the right and left caudate nucleus compared to low-sensitization responders.
• Differences in brain activity and structure correlated with the secondary hyperalgesia phenotype.

Conclusions:

• Brain structure and neuronal responses to noxious stimuli differ based on secondary hyperalgesia phenotype.
• These findings indicate phenotypical variations in central sensitization.
• Differences in central sensitization may predict susceptibility to acute and persistent pain.