tc,
Very sorry to hear that your mother has been diagnosed with ALS. I'm sure you are in shock after reading what may be in store for her and your family's future. It will probably be a while til you begin to accept her fate and you will be able to move beyond feelings of despair.
If you use the search button near the top of the page you will find info about lithium on this site.
I can only give you the account of my husband's experience with lithium...It is no magic bullet. He started lithium on 02/22/08. Improvements: Hardly any cramping in throat when yawning. Less coughing/gagging. Can now use left fingers to type once again and can write better with left hand now (left handed). Voice is a lot clearer and doesn't have to repeat himself as often as before. More energy! Side effects: Dry mouth, a little gas, and increased fasciculations.
His lithium level was at .2 but has decreased to .1. I think the reason for this is diet, as he went away for a few days and had a change in diet. He remains on 150mg twice daily for now.
These improvements may seem small, but he is thoroughly thrilled to be able to use his fingers on his left hand more than anything!
Good luck to you and your mother. And please feel free to ask any more questions you may have. We are all here to support each other!