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".

• Sphenopalatine Ganglion Block with Local Anesthetic (Procedure): Block performed with bilaterally inserted q-tips with 1:1 mixture of lidocaine 40mg/ml and ropivacaine 5mg/mL
• Sphenopalatine Ganglion Block with Placebo (Isotone NaCl) (Procedure): Block performed with bilaterally inserted q-tips with isotone NaCl
• "Sham"-block with Placebo (Isotone NaCl) (Procedure): Block performed with bilaterally inserted q-tips with isotone NaCl. The q-tips are inserted a maximum of 3 cm into the nasopharynx thus not reaching the mucus above the ganglion.

Primary outcomes

• Hyperactivity in the sphenopalatine ganglion assessed by pain intensity (0-100mm on a visual analogue scale, VAS) of the postdural headache in standing position in the group Ropivacine-Lidocaine and "sham". [30 minutes after block]: Pain intensity will be measured as worst experienced pain after the patient has been standing for 30 seconds or the worst experienced pain while attempting to stand if the rating has to be interrupted.

Secondary outcomes

• Number of patients with pain rating below 30mm in standing position (0-100mm on a visual analogue scale, VAS) [30 minutes and 1 week after block]: Pain intensity measured as worst experienced pain after the patient has been standing for 30 seconds or the worst experienced pain while attempting to stand if the rating has to be interrupted.
• Worst experienced pain in standing position (0-10 on a numercial rating scale, NRS) [During study period until completion of 1 week follow up]: The worst experienced pain reported during the week following the block as registered by the patient.
• Average pain intensity (0-10 on a numercial rating scale, NRS) [During study period until completion of 1 week follow up]: The average pain intensity reported during the week following the block as registered by the patient.
• Number of patients needing "rescue GSP-block" [At 1 week follow up]: If the patient at the 1 week follow up still needs further treatment a "rescue SPG-block" defined as a new SPG-block with "open label" analgetics will be offered.
• Hyperactivity in the sphenopalatine ganglion assessed by pain intensity (0-100mm on a visual analogue scale, VAS) of the postdural headache in standing position in all 3 groups. [30 minutes after block]: Pain intensity will be measured as worst experienced pain after the patient has been standing for 30 seconds or the worst experienced pain while attempting to stand if the rating has to be interrupted.

Other outcomes

• Analgesics used daily in the week following the SPG-block [During study period until completion of 1 week follow up]: The use of analgesics during the week following the block as registered by the patient and the patient file.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Age > 18 years
* Moderate to severe headache (NRS >= 3) with self reported duration of minimum 6 hours during the past week as well as moderate to severe headache (NRS >= 3) on the day of intervention.
* Onset of headache during or maximum 4 weeks after PCR-verified COVID-19 infection.
* Headache must have persisted for at least 4 weeks following COVID-19 diagnosis.

Exclusion Criteria:

* Patients who cannot cooperate to the study
* Patients who does not understand or speak Danish
* Allergy to the drugs used in the study
* Has taken opioids within 12 hours prior to intervention
* History of migraine or persistent headache before COVID-19 infection.
* Active COVID-19 infection (defined by the Danish Goverment regulations, i.e. 48 hours after last symptoms (omitting long term effects) or 7 days after positive COVID-19 test if no symptoms.

• Christian S Meyhoff, PhD, Study director, University Hospital Bispebjerg and Frederiksberg