What Causes Numbness In The Arm, Back And Legs?

My mother used to feel onesided numbness in arm, back.... frequently,

she used to report muscle cramps in leg... sometimes... and headache...

now she is feeling numbness in the other arm also... She is working too

hard physically as both going to work and looking after bedridden father

for past 9 months... She is reporting the above syptoms for past 2 or 3 months only... Her age is 56. Please tell us what her problem might be