Alvanian spine mites were tiny parasitic arachnids which burrowed into humanoid spinal columns, causing back pain for life.
Odo mistook a pinched nerve for Alvanian spine mites in 2373. (DS9: "The Begotten")
According to the script, Alvanian was pronounced as "al-VEIN-ee-un". 
According to the RPG sourcebook Creatures, the Alvanian spine mite is a tiny crustacean that lives inside the spinal columns of larger animals and feeds on neural energy.