I don't currently own a dog (no room, no time) but my father owned a beautiful, pedigreed Boxer he exhibited in shows, including the big AKC show at Madison Square garden. 'Luke' was our family pet. My dad was also a volunteer dog obedience trainer and I often assisted him. So, I grew up with a very special dog and learned to love dogs. Still do. To this day, I relate very well to almost any dog I encounter. That dogs can sense an owner's mood is fairly well-established. That they may somehow intuit an acoustic neuroma is well within the sphere of reason. Dogs survive on instincts, fantastic hearing and olfactory abilities. That a dog may 'sense' something 'wrong' on their owners body - even an acoustic neuroma - is not at all unimaginable. I can accept the possibility, based on the circumstantial evidence presented.
Jim