Chronic pancreatitis patients show hyperalgesia of central origin: a pilot study.

Background: The pain of chronic pancreatitis remains challenging to manage, with treatment all too often being unsuccessful. A main reason for this is lacking understanding of underlying mechanisms of chronic pain in these patients.
Aim: To document, using somatic quantitative sensory testing, changes in central nervous system processing (neuroplasticity) associated with chronic pancreatitis pain and thus gain insight into underlying pain mechanisms.
Patients and Methods: We studied 10 chronic pancreatitis patients on stable opioid analgesic medication. Ten matched surgical patients without pain served as controls. Pain verbal numeric rating scores (NRS) and thresholds to electric skin stimulation and pressure pain were measured in dermatomes T10 (pancreatic area), C5, T4, L1 and L4.
Results: The pancreatitis patients had a median NRS pain score of 5 (range 3-8). Electric sensation and pain thresholds were significantly increased in the pancreatic region, tending to be more so in female pancreatitis patients. Pressure pain thresholds were significantly lower in pancreatitis patients than in controls, with men tending towards greater generalised relative hyperalgesia than women.
Conclusions: Chronic pancreatitis patients show pronounced generalised deep hyperalgesia that is present despite opioid therapy. These signs, consistent with central sensitisation, appear relatively more prominent in men than women. There is also evidence suggesting that women may have a better segmental inhibitory response than men, possibly explaining their relatively less prominent generalised deep tissue hyperalgesia compared to men.