Lack of correlation between vasodilatation and pharmacologically induced immediate headache in healthy subjects

Background: The causal relationship between experimental headache and vasodilatation has not been fully clarified. In the present study, we combined headache and vascular data from eight experimental studies and conducted detailed statistical analyses. Given that substances used in all these experiments were vasodilators we examined a possible correlation between headache scores and increases in arterial diameter. Methods: We identified nine studies and retrieved raw data in 89 healthy subjects (46 females, 43 males), mean age 27 years (range 18-59 years). The following variables were collected: maximal median headache intensity scores on a verbal rating scale (VRS) during immediate headache (0-120 minutes); the mean velocity of blood flow in the middle cerebral artery (V-meanMCA); and the diameter of the frontal branch of the superficial temporal artery (STA) during the maximal median headache intensity. Results: The scatter plots show no relationship between maximal headache score and the relative changes in V-meanMCA and diameter of the STA. The main analyses of covariance showed a significant effect only of heart rate on headache (p = .014). The interaction tests were insignificant for all variables. Conclusions: The major outcome is a finding of no linear relationship between experimental immediate headache and dilatation of the MCA or STA.