Pressure pain sensitivity mapping of the temporalis muscle revealed bilateral pressure hyperalgesia in patients with strictly unilateral migraine

Previous studies on pressure pain sensitivity in patients with migraine have shown conflicting results. There is emerging evidence suggesting that pain sensitivity is not uniformly distributed over the muscles, indicating the existence of topographical changes in pressure pain sensitivity. The aim of this study was to calculate topographical pressure pain sensitivity maps of the temporalis muscle in a blind design in patients with strictly unilateral migraine compared with controls. For this purpose, an electronic pressure algometer was used to measure pressure pain thresholds (PPT) over nine points of the temporalis muscle: three points in the anterior, medial and posterior parts, respectively. Pressure pain sensitivity maps of both sides (dominant or non-dominant; symptomatic or non-symptomatic) were calculated. The analysis of variance showed significant differences in PPT values between both groups (F = 279.2; P < 0.001) and points (F = 4.033; P < 0.001). Patients showed lower PPT at all nine points than healthy controls (P < 0.001). We also found lower PPT in the centre of the muscle compared with the posterior part of the muscle within both groups (P < 0.01). Interaction between group and points (F = 1.9; P < 0.05) was also found. Within the migraine group, PPT levels were decreased bilaterally from the posterior to the anterior column of the temporalis muscle (Student-Newman-Keuls analysis; P < 0.05), with the most sensitive in the anterior part of the muscle. For controls, PPT did not follow such anatomical distribution, the most sensitive point being the centre of the mid-muscle belly. This study showed bilateral sensitization to pressure in unilateral migraine, suggesting the involvement of central components.