The Effect of Ganglion Sphenopalatine Block Versus Placebo on Persistent Headache Following COVID-19 Infection

Adult patients with persistent headache following COVID-19 infection will be enrolled in the study. The patients will be randomised into three groups; bilateral SPG-block withto receive local anesthetic (lidocaine + ropivacaine), bilateral SPG-block with placebo (isotone NaCl) or bilateral "sham"-block with placebo (isotone NaCl). Primary outcome is hyperactivity in the sphenopalatine ganglion assessed by pain intensity (0-100mm on a visual analogue scale, VAS) of the headache in standing position 30 minutes after block in the group Ropicavain-Lidocain and "sham".