Neck Dissections (ND) are preformed to remove any lymph nodes downstream from a primary cancer. The lymph system acts as a natural seize that captures cancers cells that break free of the primary cancer site. Generally they are only done on the side of the neck that the primary cancer was found.
I had a stage one cancer of the soft palet and was borderline for a ND. Both my ENT and RO felt I would not need the ND due to how early the cancer was found. I did radiation only to the primary site with extra doses of radiation to the lymph nodes just in case an errant cell made it that far.
I wish I had insisted on the ND as I did suffer a recurrence of cancer in a lymph node deep in my neck. The cancerous node grew right around the carotid artery before we discovered it. At that point I was no longer eligible for a surgical solution as removing the cancer would involve removing the carotid and instant death.
Obviously I am one who will always advocate for the ND being done although I have no experience with either the procedure or the after effects.
There are many here who can help you with ND�s and there effects. I have heard of a number of people right here on this site who had the ND and multiple nodes removed with no sign that the cancer had spread. But you have to keep in mind it only takes one cancer cell in one node to make recurrence a reality. If I had had one I would be in much better shape today.