what the significance of a failed tip-toe and heel walks are?

I went to see a new GP (thanks BTW, to everyone who responded to my DO vs MD post- I really like this new DO-doc). He asked me to walk on my heels- which not even my neuro had asked me to do 2 years ago. I cannot do it. I can lift the toes on my right foot, but not the left, and have no balance. When I try to walk on high tip-toe, I cannot move forward (like 3" a step) and cannot get my knees to bend or stay balanced at all. I had not been aware that I couldn't do it prior to this appointment, so it was a little shocking.

What brain/muscle functions are these 2 walks testing? What exactly does it mean if a person cannot do them? Are there diseases/dysfunctions that are commonly associated with them? I did a google-search and came up with nothing- just that a patient should be asked to do them.

Thanks again for any response!!

elle