Chronic pain assessment using heat beam dolorimetry.

The heat beam dolorimeter (HBD) was developed to evaluate cutaneous pain thresholds in humans. In the present study, the hypothesis that a patient's underlying pain status affects his pain tolerance to an incident HBD stimulus was tested. Twenty-seven chronic pain patients with a variety of clinical problems unresponsive to conventional algological therapy were scheduled for neurosurgical procedures. These patients were evaluated pre- and postoperatively by the HBD procedure. On initial testing, drug-free pain patients showed significantly higher pain tolerance thresholds than normal volunteers (P less than 0.02, Mann-Whitney U test). Postoperatively, incident pain tolerance thresholds in the HBD test were reduced from pre-surgical levels in these patients and were indistinguishable from the second evaluation latencies of volunteers (P greater than 0.05). Twenty-four of the 27 patients reported significant pain relief following surgery. Our results show that, in chronic pain patients, endogenous pain significantly affected incident pain perception in the HBD test when compared with the responses of normal pain-free volunteers. Consequently, HBD may be useful in objectively assessing chronic pain and its relief by neurosurgical procedures.