Preventive treatment with CGRP monoclonal antibodies restores brain stem habituation deficits and excitability to painful stimuli in migraine: results from a prospective case-control study

BACKGROUND & OBJECTIVES: Calcitonin gene-related peptide ligand/receptor (CGRP) antibodies effectively reduce headache frequency in migraine. It is understood that they act peripherally, which raises the question whether treatment merely interferes with the last stage of headache generation or, alternatively, causes secondary adaptations in the central nervous system and might thus possess disease modifying potential. This study addresses this question by investigating the nociceptive blink reflex (nBR), which is closely tied to central disease activity, before and after treatment with CGRP antibodies. METHODS: We enrolled 22 patients suffering episodic migraine (21 female, 46.2 ± 13.8 years of age) and 22 age-/gender-matched controls. Patients received assessments of the nBR (R2 component, 10 trials, 6 stimuli/trial) before (V0) and three months (V3) after treatment with CGRP antibodies started, controls were assessed once. The R2 area (R2a) and habituation (R2h; gradient of R2a against stimulus order) of the stimulated/non-stimulated side (_s/_ns) following repeated supraorbital stimulation provide a direct readout of brainstem excitability and habituation as key mechanisms in migraine. RESULTS: All patients showed a substantial reduction of headache days/month (V0: 12.4±3.3, V3: 6.6 ± 4.9). R2a_s (F(global)=5.86, p<0.001; block 1: R2a_s: -28%, p<0.001) and R2a_ns (F(global)=8.22, p<0.001, block 1: R2a_ns: -22%, p=0.003) were significantly decreased, and R2h_ns was significantly enhanced (F(global)=3.07, p<0.001; block 6: R2h_ns: r=-1.36, p=0.007) from V0 to V3. The global test for changes of R2h_s was non-significant (F(global)=1.46, p=0.095). Changes of R2h significantly correlated with improvement of headache frequency (R2h_s, r=0.56, p=0.010; R2h_ns: r=0.45, p=0.045). None of the nBR parameters assessed at baseline predicted treatment response. DISCUSSION: We provide evidence that three months of treatment with CGRP antibodies restores brain stem responses to painful stimuli and thus might be considered disease modifying. The nociceptive blink reflex may provide a biomarker to monitor central disease activity. Future studies should evaluate the blink reflex as a clinical biomarker to predict treatment response at baseline and to establish the risk of relapse after treatment discontinuation. TRIAL REGISTRATION: This trial was prospectively registered at clinicaltrials.gov (ID: NCT04019496, date of registration: July 15, 2019).