Cluster headache pathophysiology: What we have learned from advanced neuroimaging.

BACKGROUND: Although remarkable progress has been achieved in understanding cluster headache (CH) pathophysiology, there are still several gaps about the mechanisms through which independent subcortical and cortical brain structures interact with each other. These gaps could be partially elucidated by structural and functional advanced neuroimaging investigations. OBJECTIVE: Although we are aware that substantial achievements have come from preclinical, neurophysiological, and biochemical experiments, the present narrative review aims to summarize the most significant findings from structural, microstructural, and functional neuroimaging investigations, as well as the consequent progresses in understanding CH pathophysiological mechanisms, to achieve a comprehensive and unifying model. RESULTS: Advanced neuroimaging techniques have contributed to overcoming the peripheral hypothesis that CH is of cavernous sinus pathology, in transitioning from the pure vascular hypothesis to a more comprehensive trigeminovascular model, and, above all, in clarifying the role of the hypothalamus and its connections in the genesis of CH. CONCLUSION: Altogether, neuroimaging findings strongly suggest that, beyond the theoretical model of the "pain matrix," the model of the "neurolimbic pain network" that is accepted in migraine research could also be extended to CH. Indeed, although the hypothalamus' role is undeniable, the genesis of CH attacks is complex and seems to not be just the result of a single "generator." Cortical-hypothalamic-brainstem functional interconnections that can switch between out-of-bout and in-bout periods, igniting the trigeminovascular system (probably by means of top-down mechanisms) and the consensual trigeminal autonomic reflexes, may represent the "neuronal background" of CH.

Refractory migraine profile in CGRP-monoclonal antibodies scenario.

OBJECTIVE: Refractory migraine (Ref-M) represents a conundrum that headache experts have to face with. We aim to investigate whether a peculiar profile may characterize patients with Ref-M according to 2020 European Headache Federation criteria. Furthermore, to substantiate a dysfunctional dopaminergic pathway involvement in these patients, we explored the effectiveness of olanzapine. MATERIALS & METHODS: Eighty-four patients (fitting previous Ref-M criteria of the 2014) were treated with erenumab for six months. Differences between clinical and demographic features of responder (Ref-M according to 2014 criteria) and not-responder (Ref-M according to 2020 criteria) patients to CGRP-mAbs were investigated and their predictive values assessed. In fifteen patients with Ref-M not responders to CGRP-mAbs, olanzapine was administered (5 mg/die) for 3 months and frequency and pain intensity of migraine attacks were estimated. RESULTS: Patients with Ref-M not responsive to CGRP-mAbs (29/84) when compared with Ref-M responsive to CGRP-mAbs showed higher baseline frequency of migraine attacks, medication overuse and pain catastrophizing scale (PCS) scores. Logistic regression analyses showed that frequency of attacks, medication overuse and PCS score represent independent negative predictors of CGRP-mAbs response. A ≥50% reduction of headache days/month was observed after olanzapine treatment in 67% of patients with Ref-M not responsive to CGRP-mAbs. CONCLUSIONS: We outline that higher frequency of migraine attacks, medication overuse and pain catastrophizing characterize patients with Ref-M not responsive to CGRP-mAbs. In this frame, olanzapine effectiveness on frequency and pain intensity of migraine attacks supports the hypothesis that migraine refractoriness may be subtended by a prominent involvement of the dopaminergic pathway.

Additive Interaction Between Onabotulinumtoxin-A and Erenumab in Patients With Refractory Migraine.

In the last decade, notable progresses have been observed in chronic migraine preventive treatments. According to the European Headache Federation and national provisions, onabotulinumtoxin-A (BTX-A) and monoclonal antibodies acting on the pathway of calcitonin gene-related peptide (CGRP-mAbs) should not be administered in combination due to supposed superimposable mechanism of action and high costs. On the other hand, preclinical observations demonstrated that these therapeutic classes, although operating directly or indirectly on the CGRP pathway, act on different fibers. Specifically, the CGRP-mAbs prevent the activation of the Aδ-fibers, whereas BTX-A acts on C-fibers. Therefore, it can be argued that a combined therapy may provide an additive or synergistic effect on the trigeminal nociceptive pathway. In the present study, we report a case series of 10 patients with chronic migraine who experienced significant benefits with the combination of both erenumab and BTX-A compared to each therapeutic strategy alone. A reduction in frequency and intensity of headache attacks (although not statistically significant probably due to the low sample size) was observed in migraine patients treated with a combined therapy with BTX-A and erenumab compared to both BTX-A and erenumab alone. Moreover, the combined therapy with BTX-A and erenumab resulted in a statistically significant reduction in the symptomatic drug intake and in migraine-related disability probably related to a reduced necessity or also to a better responsiveness to rescue treatments. Present data suggest a remodulation of current provisions depriving patients of an effective therapeutic strategy in peculiar migraine endophenotypes.