Pain in the head and neck after radiotherapy

Hi, I am writing to you for my father who, after having been operated on to remove a carcinoma of the tongue with hemiglossectomy, underwent 30 sessions of radiotherapy to the neck for a total dose of 600 cGy. The radiotherapy ended in May, the problem is that as late side effects appeared in the summer on the neck just below the cut scar, fibrosis, i.e. hardening of the tissues and also redness and pain in the cervical vertebrae , these cause pain in both the neckthat to the head causing it continuous and disabling headache. Furthermore, 5 months after the end of the treatment, both the neck and the face are still red. For the pain we tried cortisone, various analgesics, phosphorylase injections (Vit B complex), cartinitine injections, but with poor results. Is there something natural maybe that you can apply locally on the neck and on the inflamed parts? There seems to be no solution to these pains and this seems absurd to me! A thousand thanks