Please tell me if there is a cure for fatal/sporadic fatal insomnia?

Regretfully no: Regretfully there is no cure as of yet. Gene therapy has also been unsuccessful. It is a rare prion disease that is usually inherited, so it is very rare to be diagnosed with it. If you are concerned about it, it is recommended you consult your physician to go over a detailed history and examination to properly evaluate your symptoms. Insomnia due to other causes are more common. Hope that helps!