How do you decide whether to locally excise vs deroof a persistent draining tunnel in a patient with otherwise medically optimized HS?  

Great question. Both are great options. I usually try for a deroofing since it's a shorter healing time, but it doesn't always work out. If you can find an opening to the tunnel, that helps a lot. It gives you the opportunity to probe and a place to begin your incision. Both of those help you get in...