Evidence for Generalized Hyperalgesia in Chronic Fatigue Syndrome: A Case Control Study.

Several studies provided evidence for generalized hyperalgesia in Fibromyalgia or Whiplash
Associated Disorders. In Chronic Fatigue syndrome however, pain is a frequently reported
complaint, but up to now evidence for generalized hyperalgesia is lacking. The aim of this
study is to examine whether the pressure pain thresholds (PPTs) at both symptomatic and
asymptomatic sites differ in CFS patients with chronic pain, compared to healthy controls.
Therefore thirty CFS patients with chronic pain and thirty age and gender matched healthy
controls indicated on a Margolis Pain Diagram where they felt pain lasting longer than 24
hours in the past 4 weeks. After completing a test battery of questionnaires evaluating pain
cognitions, functional status and symptomatology, a blinded researcher assessed PPTs
bilaterally at 7 non-specific sites on both trunk and extremities. PPTs were compared for the
two complete groups. In addition, PPTs of patients and controls who did not report pain in a
respective zone were compared.
PPTs of the patients were significant lower (p <.001) compared to these of the control group,
also when pain free samples per zone were compared (p <.001). The mean PPT in all CFS
patients was 3.30 kg/cm² and 8.09 kg/cm² in the controls. No confounding factors responsible
for the observed differences, as e.g. catastrophizing and depression, could be revealed.
These findings provide evidence for the existence of hyperalgesia even in asymptomatic areas
(generalized secondary hyperalgesia). The generalized hyperalgesia may represent the
involvement of a sensitized central nervous system.