This has triggered a memory. Initially I thought 'no connection' then remembered: at certain times of the month my wisdom teeth would ache so much that I was unable to eat: even after they were removed, every month the sockets would be very painful - they were removed in 1981. [teeth not sockets ;-)]. This went on for many years, probably 10 or more B4 it settled down Some1 could have written a Thesis!