What Causes Sudden Tremors And Numbness In Lower Half Of Body?

Last night I had a scare that never happened before.i was walking holding my 2yr old when all of a sudden my knees & legs started violently twitching and thrashing all around, so much I lost my balance and had to stop walking. As soon as I stoped walking the twitching subsided but from my waist down I lost all feeling. My legs quickly collapsed on me and I fell hard and fast. I knew I was falling and I still had feeling in my upper body which allowed me to hold my baby tight enough to protect him from the drop. After landing w/ a thud onto my legs, back , & head I slowly got up and walked away knowing THIS WAS NOT ANYWHERE NORMAL? It almost felt like a seizure to my lower part of my body? Can you please give me so answers??? Thanks Jennifer Debolt