Physical therapy. Stretching exercises. If present prior to treatment, it is unlikely to improve. It will likely be a chronic problem. 

This is not an insignificant, albeit and often overlooked complication of head and neck irradiation. This side effect risk is especially heightened in patients with tumors in the retromolar trigone area (RMT) and those with disease extensions to the pterygoids (either muscle or plates). The incidenc...

Referral to a physical therapist (PT) and to a speech-language pathologist (SLP) who are familiar with H&N cancer patients. Most impact on treatment can happen with the first few PT sessions. Earlier intervention could be helpful but no data to specifically support that. And I am unaware of anyt...