Hello. I'm not sure whether this is related to the neurological disorders but hopefully somebody can help.

my friend's mother who is 80 year olds fell down a few years ago and diagnosed for the vertebra fracture (T8-10). But after that she is fine and she can walk as normal.

2 months ago she started to feel pain at the lower back and the MRI shows that L3-5 fractures (this time she didn't have any trauma)

after 2 weeks of bed resting, she started to be unable to walk. And both of her legs jerk at least 10 times per hour, especially getting serious in mid night, which makes her difficult to sleep. The jerk is vigorous, and always need her family to pull them straight. We've consulted different doctors but they just can't find out what happened. All of them tell that it's not life threatening and so there is no treatment. Can anyone suggest me the possible illness of this so that we can find some specialsts to help my friend's mother?

Millions thanks!