My senior cat has a leaking growth between his ears. What to do?

Hi there and thank you for using pet coach to address your concern. In the photos you provided this appears to be what looks like a cyst to me. Many times these cysts are the nine and occur with age. If you do not want to put him through any major testing you could still have him examined by a veterinarian and the vet you have a look at him can stick a small needle into the cyst and drain the contents. This does not generally require any sedation and is typically well- tolerated by cats. Most likely the cyst will fill back up, but I have several patients that are older where the owners do not want to put them through any major testing or surgery and elect to bring the animal in every so often to have the cyst drained. I would discuss this with your veterinarian and see if this is something that he or she would do. I hope this helps guide you in the right direction. Please feel free to contact me if you have any further concerns.