I have been searching for some sort of answer for you, and I understand the attachment to plants!
Here is a link I found that does say that you could top off the Ponytail. I will let you decide if this is something you may want to try.
I also might recommend checking with your local extension service. They may have information relating to weather conditions this past winter. Did the cold temperatures affect your area?
Our ponytail has been outside in the same location for more than 15 years. No sign of infestation. Light and watering have been the same. This is sad as it's almost 6 feet tall and we've had it so long. Thank you for your time!
You should not top off a Ponytail Palm. Is this plant in a pot or the ground?
Is the plant receiving adequate water, lighting? Have you inspected the plant for any other signs of decease or insects?
I have listed 2 very good links with more information.