Hi there... this is not an uncommon occurrence when dealing with this cancer. Sadly some drs only remove the effected areas and don't do a prophylactic partial neck dissection. The reality is that a lot of the time the cancer is hiding in the nodes and isn't detected on a scan because it's too small.

Thankfully he's had the dissection now. the carotid involvement is unfortunate but a few people here (PAULB) have had that issue as well. Rads and chemo is not fun but as someone else said. it is doable. Just read up on what to expect and plan for the worst and hope for the best.

Hugs and welcome and so sorry you are going through this again.