See these references:
http://www.merriam-webster.com/netdict/idiopathic
THis one is cool as it cites many sources:
http://medical-dictionary.thefreedic...com/idiopathic

Essentially it's as many here have said often: Don't know, havn't a clue!
Next step for you is to go thru the whole self-assessment of diagnostics and symptoms from this source and then start to numb your brain with all the 'possibles', narrowing it down to likelies or probables... http://neuromuscular.wustl.edu/alfindex.htm
It's essentially what I call 'brain wrestling' time.
Only you can do the work to sort it out? It's work, I guarantee you, but knowing what you are dealing with helps you get on with LIFE!
It's not easy, but doing the research at least helps you understand what all is going on! Hope and patience! - j