I visited my neurologist yesterday.  I have to be evaluated every six months for migraines and to make sure that my tremors are benign and that I do not in fact have Parkinson's.  They have been determined to be "essential tremors."

I asked my neurologist "What does that mean, 'essential'?"  He answered, "It means that essentially we have no idea what causes them."

Nothing like having doctors with a sense of humor.