Chronic Migraine: A Narrative Review on the Use of Botulinum Toxin with Clinical Indications and Future Directions.

Chronic migraine belongs to the "chronic long-duration headaches", and it is associated to high burden and significant economic impact. Treatment for both episodic (EM) and chronic migraine (CM) is based on the management of acute attacks and their prevention. For moderate/severe attacks, pharmacological therapies are triptans, dihydroergotamine nasal sprays or injections or neuroleptics, non-steroidal anti-inflammatory drugs, and corticosteroids. Chronic migraine belongs to the "chronic long-duration headaches", and it is associated to high burden and significant economic impact. Treatment for both episodic (EM) and chronic migraine (CM) is based on the management of acute attacks and their prevention. For moderate/severe attacks, pharmacological therapies are triptans, dihydroergotamine nasal sprays or injections or neuroleptics, non-steroidal anti-inflammatory drugs, and corticosteroids. The pathophysiology of CM is characterized by an abnormal activation of the trigemino-vascular system in the meninges causing a neurogenic inflammation, which explains the use of anti-inflammatory during attacks. It seems that the objective of the preventive therapy with the botulin toxin OnaBoNT-A consists in interrupting the release of CGRP and other neuropeptides as well as the activation of C-fiber nociceptor and of the nearby A-delta fibers. The protocol for migraine treatment with OnaBoNT-A injections consists of 31-39 pericranial injection sites involving seven muscle groups bilaterally in specific areas of the head and neck, with a total dose of between 155 and 195 units, every three months. The severe adverse events reported with high doses of botulin toxin for spasticity, have not been reported for CM treated with OnabotA at the labeled dose. The established improvement with onabotulinumtoxinA treatment in CM patients had a positive impact not only in reduction monthly headache days but also in improving quality of life, with reduction in both healthcare resource utilisation (HRU) and work impairment. Aim of this review was to give an overview on the use of BoNT-A in patients with CM, giving practical advices on the clinical indications.