Question
I have an eight year old cactus, 3 ft wide, 3 ft tall, potted.  I don't know what type it is, but it branches out in all directions, all from one trunk about 4" in diameter.  I put it outside when the weather hit 80, then the evenings dipped, so I brought it back in.  During both moves, unfortunately, it was dropped.  It was punctured in many places by it's own needles, bled a milky white substance, and now each of those branches is turning brown.  Help please, I don't want to lose it.  

Answer
Elaine,

It sounds like you actually have a Euphorbia, which is similar to a cactus, but isn't one. They are very sensitive to cold and over watering. Is it possible that it was left out in below 40 degree weather? If so, that could be the problem. If the damage was from it's own spines, it should heal. If it was exposed to low temps as well, It may still survive. Let the plant go for a few weeks and monitor whether it looks better or worse.

Please follow up with me at that time and let me know its condition. Hope this helps.

Sincerely,

Greg