Lack of Neuro Cell

Respected Doctor,

Iam  36 years old male. I have muscle loses and feel too soft in triceps in right hand. I also feel some weight loss in the right hand only, and could not lift from shoulder to top even with a small weight(but normally I could).
I have beeen diagnosed by a neurologist and he reported me it is due to lack of neuro cells.
Everything normal in MRI scan.
Two of my fingers in right hand(middle and ring finger) is dis functioning and feeling some strokes(rarely) in next two fingers. I need to know what causes this disease and how to get treated.

Thanking you
Regards
Ceesar