I had three neck dissections, two radical, and the last with a pec flap. I have stiffness, swelling, and limited range of motion in the neck, but manage without anything. I did do physical therapy a few times, basically for leg strength, neuropathy, walking, with a few exercises for the neck, and shoulder, being they took my neck muscle out. I notice my posture, and left shoulder is different from the RND. Some do lymphatic lymph drainage, acupuncture, physical therapy, but check with your doctor.

The radiation symptoms will differ based on the sites radiated, and the dosage amount. Usually the first time is up to 70Gy or slightly above, and reirridation is usually less, and usully to more targeted areas, which may not involve the oral or oropharyngeal area like the first time, which effects speech, chewing, swallowing, so it's different, but may have mote added side effects in the neck this time around due to the total radiation received.

Good luck with your recovery.