Why There Is Loss Of Sensation In The Hand And Arm?

Hi, I have just recently found out that my Father-in-law has a crumbling spine. Also, even though he is on the acute stroke recovery ward, it has not been established that he has actually had a stroke, yet he has lost the feeling in his right hand and arm, and has been told that his muscles in his arms are wasting away. Both his brother and his sister died from motor neurone disease, but due to a simple 'pin prick' test, and maybe other factors, but this has been ruled out and we have been told that it is not m.n.d. His speech is also very slured also, and even though he is on the stroke ward, they are not sure even if it is a stroke at all, but maybe some sort of progressive nerve damaging disease. Could you shed any light on this. He also has diabetes (insulin dependant). Any advice would be appreciated. He is due for an MRI Scan some time next week - Thanks - Mark