What Causes Muscular Spasm In Calf Spreading To Thigh Followed By Backache?

my daughter aged 14 suffers from left leg -calf muscular spasm which then spreads to her thighs and then she gets back aches. She has been suffering for the last one month. The doppler tests & MRI does not indicate any cause for these spasm as informed by the orthopaediatric. He suggested it could be a case of fasciculation. Kindly advise.