Idiopathic means the same side; affecting the same side of the body.
When discussing Migraine disease and other headache disorders, we generally see ipsilateral used to describe symptoms that occur on the same side of the head or body a the headache. This can happen in Migraine, and is quite common with symptoms of cluster headache.
You can read more about some of the ipsilateral symptoms of cluster headaches in Cluster Headaches - The Basics.
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+.