Abstract text (incl. figure legends and references)

OBJECTIVES: Our aim is to evaluate if changes in sensitization and habituation measured with algometry might be a biomarker for response to OnabotulinumtoxinA (OnabotA) in patients with chronic migraine (CM).

METHODS: Observational prospective cohort study. OnabotA therapy (PREEMPT) was initiated in CM patients accordingly with local guidelines. An algometry study was performed prior to OnabotA treatment and after each of three sessions. Response to OnabotA was defined as a decrease of more than 50% of migraine days, compared to the baseline. A mechanical algometer was used to determine Pressure Pain Thresholds (PPT). They were measured on 21 points over the scalp (Fp1, F3, F7, C3, T3, P3, T5, O1, Fp2, F4, F8, C4, T4, P4, T6, O2, Fpz, Fz, Cz, Pz, Oz), based on the normalized positions for electroencephalogram recordings. In each point three measures were performed with a 30-second resting period between them. We considered decreasing or increasing between PPTs (kPa) in these three measures, to establish respectively a pattern of sensitization or habituation. We evaluated change of these PPTs patterns between basal and third determination.

RESULTS: 35 patients (91.4% females) were included. Mean age was 43.3 ± 9.1 years (26-60). Twenty-six (74.3%) responded to OnabotA. Basal PPTs showed in 20 points a pattern of sensitization, whilst when measured after 3 OnabotA procedures in 14 points habituation was observed. When comparing responders with no responders, differences between basal and third determination were obtained in T4 (0.05 vs -0.44, p:0.035), F3 (0.21 vs – 0.1, p:0.033) and FP2 (0.33 vs – 0.13, p:0.005)

CONCLUSION: Algometry pattern turns from sensitization to habituation in CM patients treated with OnabotA, which, in some points, correlates with response to treatment.