I have just been reading an article entitled as above, by Dr Richard P Allen, unfortunately I cannot post a link for some reason, but I believe that if you google the above title with his name you should be able to find it.
It was very interesting, they have done a study with MRI, and discovered a connection with glutamate in the thalamus, which is responsible for arousal, and think that even in those fortunate enough to have their symptoms controlled, this could be the reason for continued insomnia, which is me a T.
I hope you can understand me, I am not to great at explaining things these days, but I thought it could be interesting reading for you.
The article is published in lots of journals, Neurology today is one I think.
Good luck, an take care,