Botulinum Toxin Type A Blockade of the Sphenopalatine Ganglion in Treatment-refractory Chronic Migraine

Inclusion Criteria: The participants must meet all of the inclusion criteria to participate in this study: 1. Informed and written consent. 2. Male or female, between 18 and 70 years of age 3. Masters a Scandinavian language at level sufficient to fully understand the written and verbal study information 4. Migraine, with or without aura, fulfilling the International Classification of Headache Disorders (ICHD) III criteria 1.3. for chronic migraine at time of inclusion 5. Chronic migraine at least for a period of 1 year prior to inclusion 6. Debut of episodic migraine before the age of 50, and chronic migraine before the age of 65. 7. The condition is pharmacologically refractory as defined in this study as insufficient treatment effect, contraindication(s) or intolerable side effect(s) of at least 3 medications from at least 2 of the following medication (drug) classes 1. Beta-blockers 2. RA(A)S-inhibitors 3. Calcium-antagonists 4. Antiepileptic drugs 5. Tricyclic antidepressants 6. Botulinum toxin A 7. CGRP antagonists 8. Subject has had no change in type, dosage or dose frequency of preventive headache medications \< 3 months prior to baseline/screening, or a minimum of 5 half-lives, whichever is longer. 9. Subject agrees to maintain current preventive headache medication regimens (no change in type, frequency, or dose) during the whole study period. 10. In the case of women of childbearing potential (WOCBP) they have to commit to highly effective contraception in a period of 4 weeks after injection (for details, confer section 4.3) 11. Ability to understand study procedures and to comply with them for the entire length of the study Exclusion Criteria: All candidates meeting any of the exclusion criteria at baseline or visit 2 will be excluded from study participation: 1. Allergy or hypersensitivity reactions to marcaine, lidocaine, xylocaine, adrenaline, any botulinum toxin or similar substances. 2. Subject is unable to differentiate migraine from other concomitant headaches. 3. Subject with secondary headache conditions, with the exception of medication overuse headache. 4. Non-responder in regular clinical practice to preventive medications from ≥6 of the following 7 drug classes: 1. Beta-blockers 2. RA(A)S-inhibitors 3. Calcium-antagonists 4. Antiepileptic drugs 5. Tricyclic antidepressants 6. Botulinum toxin A 7. CGRP antagonists 5. Subject has had a change in type, dosage or dose frequency of preventive headache medications \< 3 months prior to baseline/screening, or a minimum of 5 half-lives, whichever is longer. 6. Subject has had a change in type, dosage or dose frequency of preventive headache medications during the baseline period, eg. prior to IMP administration 7. Botulinum toxin injections in the head and neck region, as part of migraine treatment or otherwise indicated on medical or cosmetic grounds, in the last 4 months before inclusion. 8. The discontinuation of CGRP-antagonists within 3 months before study inclusion or 5 half-lives, whichever is longer, 9. Participation in a clinical study of a new chemical entity or a prescription medicine within 2 months before study inclusion or 5 half-lives, whichever is longer. 10. Subject is currently participating or has participated in the last 3 months in another clinical study in which the subject has, is, or will be exposed to an investigational or non-investigational drug or device. 11. Subject has had previous radiofrequency ablation, balloon compression, gamma knife, or chemical denervation (e.g. glycerol treatments) of the trigeminal ganglion or any branch of the trigeminal nerve. 12. Subject has had previous radiofrequency ablation (including non-lesional pulsed radiofrequency), balloon compression, gamma knife, or chemical denervation (e.g. glycerol treatments) of the SPG. 13. Subject has had blocks of short-acting anaesthetics of the SPG in the last 3 months. 14. Subject is or has been treated with occipital nerve stimulation or deep brain stimulation. 15. Ongoing abuse of drugs (including narcotics) or alcohol. 16. More than 4 days of opioid use per month (including codeine and tramadol), and any use of barbiturates 17. Treatment with pharmacological substances prior to SPG-injection that may interact with BTA (aminoglycosides, spectinomycin, neuromuscular blockers, both depolarizing agents (such as succinylcholine) or non-depolarizing (tubocurarine derivates), and anticholinesterases). 18. Inadequate contraceptive use. Women of childbearing potential (WOCBP) who do not use highly effective contraception (HEC) or use other medication that may interact and/or otherwise reduce the efficacy of the contraceptive agents in use. 19. Subject has undergone facial surgery in the area of the pterygopalatine fossa or zygomaticomaxillary at the planned injection site that, in the opinion of the Investigator, may lead to an inability to properly conduct the procedure. 20. Facial anomaly or trauma which renders the procedure difficult. 21. Subject currently has an active oral or dental abscess or a local infection at the site of injection based on present symptoms. 22. Subject has been diagnosed with any major infectious processes such as osteomyelitis, or primary or secondary malignancies involving the face that have been active or required treatment in the past 6 months. 23. Patients with comorbid psychiatric disorders with psychotic or other symptoms making compliance with the study protocol difficult, at the discretion of the investigator 24. Patients exhibiting a high degree of comorbidity and/or frailty associated with reduced life expectancy or high likelihood of hospitalization, at the discretion of the investigator 25. Patients with disorders that severely inhibits lacrimation, at the discretion of the investigator 26. Patients with previous ischemic cardiovascular and cerebrovascular disorder with, in the opinion of the investigator, a moderate to high risk of new ischemic episodes. 27. Known infection or history of human immunodeficiency virus, tuberculosis, or chronic hepatitis B or C infection. 28. Subject has a history of bleeding disorders or coagulopathy, that, in the opinion of the Investigator, may lead to an inability to properly conduct the procedure. 29. Unable to stop antithrombotic medication e.g. platelet aggregation inhibitors and/or anticoagulation therapy, prior to procedure. 30. The patient cannot participate or successfully complete the study, in the opinion of their healthcare provider or the investigator, for any of the following reasons: * mentally or legally incapacitated or unable to give consent for any reason * in custody due to an administrative or a legal decision, under tutelage, or being admitted to a sanatorium or social institution * has any other condition, which, in the opinion of the investigator, makes the patient inappropriate for inclusion in the study 31. The patient is a study centre employee who is directly involved in the study or the relative of such an employee.