I Just Experienced A Numbness In My Left Leg. It

I just experienced a numbness in my left leg. It extended from my butt to my toe tips. It felt a bit like what happens when an extremity "goes to sleep"...but a lighter, tingly feeling. I have no pain. Not in that leg or anywhere else in my body. I did the usual things suggested to determine if I was having a stroke...smile, lift arms over my head, speak...everything worked fine. This numbness happened once or twice years and years ago...maybe 10 years. What could cause this?