Pain perception and modulation in acute and chronic pain states

Abstract

This thesis describes the evaluation of pain perception in acute and chronic pain patients and the strength of the endogenous pain modulation system in chronic pain patients. Additionally, pain phenotypes are determined in patients with chronic pain.

The ability of patients with acute pain after surgery and patients with fibromyalgia to consistently score random painful stimuli on a numerical rating scale is assessed, and the influence of opioids on this ability is evaluated. In patients with fibromyalgia, the offset analgesia paradigm is also evaluated. Offset analgesia is defined as the reduction in pain perception after a small decrease in a nociceptive heat stimulus, that is larger than would be expected from the magnitude of the stimulus decrease. This paradigm can be used to assess the endogenous ability to modulate incoming pain signals. Another manifestation of endogenous pain modulation is conditioned pain modulation (CPM). This is the reduction of pain perception of a nociceptive stimulus by the application of a second nociceptive stimulus on a remote area on the body. In this thesis the ability of a new device specifically developed to induce CPM is evaluated.

In the last 2 chapters, the signs and symptoms of chronic pain patients with fibromyalgia, diabetes and sarcoidosis are used to construct 4 pain phenotypes. These phenotypes represent groups with more homogeneous patterns of signs and symptoms, which may be important to identify and evaluate targeted drug therapy.