Yoga classes , spondylosis ,

Hi, a few days back my mother had a little accident during her yoga classes. She has consulted a neurologist and has been diagnosed with spondylosis. He has advised her that it is age related and the cause was the sudden change in posture that caused her guidiness and tingling sensation in her left arm. However, since today morning she is experiencing a nerve pull in her left leg which is from her thigh to heel. There is pain and she looses her balance. The nerve pull and loss of balance lasts for a second, however it occured about 20 times today. Please advise what the reason coud be for this condition. Should I have some tests done, if yes kindly advise which ones. Thanks in advance for your time.