After suffering a very painful attack involving my trigeminal nerve , I found from the internet that our nerves are wrapped with an insulating white fat called MYELIN . Us elders eat less animal protein, the source of B12 which makes myelin. Also our smaller stomachs have less acid which releases B12. Then of course alcohol nulls the lining of our 20 ft intestine preventing absorbsion .
My pain went away after taking B12 daily.
Good luck, James.