Pain thresholds in daily transformed migraine versus episodic migraine headache patients

Abstract

Objective: The objective of this study was to test whether pain thresholds of patients with episodic migraine (EM) are significantly different from transformed migraine (TM) patients as measured by Quantitative Sensory Testing (QST) and Semmes-Weinstein Monofilaments (SW).

Background: Although there are many theories, none have undeniably proven why many TM patients are refractory to triptans and other gold standard medications. The hypothesis was that baseline pain thresholds of TM patients are lower than EM patients.

Methods: Episodic (n = 40) and Transformed (n = 41) migraineurs with and without aura were examined with QST and SW over eight locations (bilateral ophthalmic, maxillary, C4/posterior neck, and forearm). All patients completed two visits, baseline and severe migraine.

Results: TM patients have lower pain thresholds, than EM patients, as measured on QST and SW testing. A total of 81 out of 129 patients completed both parts of the study at baseline and severe migraine. There were significant differences (P < .05) between EM and TM groups at baseline on maxillary, neck (EM = 45.91 degrees C and TM = 42.94 degrees C), and arm.

Conclusions: TM patients, clinically known to report skin hypersensitivity during migraine, were found to have lower pain thresholds than EM patients, both with severe migraine, and at baseline, measured by QST and SW mechanical testing. As with Burstein's work in EM patients with lowered pain thresholds during their acute migraine, central sensitization may be the explanation for non-responsiveness to triptans in a high proportion of TM patients. The difference in pain threshold at the neck location was such a strikingly frequent difference between EM and TM patients, that this indicates the need for future research to clarify the directional relationship and the relative importance of muscular versus peripheral versus central hypersensitivity in the determination of allodynia.