Bilateral simply means affecting both sides.
When discussing Migraines and other headaches, we generally see bilateral used to describe head pain on both sides of the head as opposed to unilateral head pain. For example, tension-type headache tends to be bilateral, whereas Migraine is more frequently unilateral. Bilateral is sometimes used to describe other symptoms as well. For example, the possible tingling and numbness of the extremities sometimes experienced with Migraine is often bilateral.
Teri Robert is a leading patient educator and advocate and the author of Living Well with Migraine Disease and Headaches. A co-founder of the Alliance for Headache Disorders Advocacy and the American Headache and Migraine Association, she received the National Headache Foundation’s Patient Partners Award and a Distinguished Service Award from the American Headache Society. Teri can be found on her website, and blog, Facebook, Twitter, StumbleUpon, Pinterest, LinkedIn, and Google+.