Document Type

Presentation or Lecture

Publication Date


Conference or Event

XXI World Congress for Neurology, Vienna, Austria


Physical Therapy


Background: In patients with complex regional pain syndrome (CRPS) delayed pain flares consistently occur ten days following salient psychogenic stress episodes. Timing of latent flares suggests pain modulation via hypothalamus-pituitary-thyroid (HPT) axis hormones.

Objective: To determine if thyroxine (T4) may modulate latent stress-related neuropathic pain flare intensity, temporal relationships between daily stress, serum T4 levels, and perceived pain intensity in patients with CRPS were investigated.

Patients and Methods: Daily, for ten weeks, three patients with type I CRPS and no thyroid pathology Hx provided blood samples for T4 assay and ratings of stress and pain. Measures included visual analog pain scale, McGill pain questionnaire, and Daily Stress Scale. Blood draws yielded bound T4 and free thyroxine index (FTI) values using microplate enzyme immunoassay. Each sample was split for blind assay from two independent labs.

Results: Across patients, 14 peak stress episodes and 26 significant pain flares were reported. Each stress episode was followed ten days by a significant pain flare and free T4 values exceeding normal adult range (2.4ng/dL). Serial lag correlations were strongest between stress and pain for pain experienced ten days after peak stress episodes (r=+0.381, p< 0.05). FTI correlated strongest with stress ten days following a stressful episode (r =+0.454, p< 0.001). Same-day pain and FTI correlated at r=+0.643, p< 0.001.

Conclusions: Increased pain ten days following stressful events is related to psychogenic HPT activity in CRPS patients. Pain modulation by thyroxine may assist understanding pain fluctuation etiology and suggest new treatment avenues for managing neuropathic pain.