Neurologists don’t know. Tried a nerve block which was unsuccessful. Has been occurring for 30+ years. Get 7-10 days pain free, then slow build up
on RHS of back of neck leading to acute pain for 6-8 hours which then suddenly stops. Then wiped out for 48 hours. The cycle repeats. One neuro suggested cutting one of the occipital nerves (there are 5 apparently) to see if that helps! The intermittent-ness seems to be the puzzling thing. NSAIDs seems to reduce the frequency and severity but would prefer not to take them due to risk of stomach bleeds.