Pain may present similarly to classical trigeminal neuralgia. Jaw pain may be caused by metastatic cancer, and tumors arising from the breast, prostate, thyroid, lung, and kidney have a propensity to spread to bone in the head and neck, most commonly seen in the posterior mandible. Metastasis in the oral region may be the first indication of a distant undiscovered malignancy in up to 60% of patients. Patients with nasopharyngeal cancer report pain that may be referred to the temporomandibular joint region and masquerade as temporomandibular disorder. Orofacial pain has been reported in patients with a distant nonmetastasized cancer, most commonly in the lungs.
The mechanism of pain is thought to be involvement of the vagus or phrenic nerve. Paraneoplastic processes may present with peripheral neuropathies, particularly in patients with lung cancer and lymphoma. Neuropathies are commonly reported in patients with malignancy (1.7%–5.5%) because of the direct effects of the tumor, paraneoplastic syndromes, and treatment-related toxicities.
Orofacial Pain due to Cancer Management
The most common acute oral side effect of radiation therapy and/or cancer chemotherapy is oral mucositis. Oral mucositis and associated pain are the most distressing symptoms reported by patients receiving head and neck radiation therapy and aggressive neutropenia-inducing chemotherapy regimens. Combined chemotherapy and radiation therapy results in increased frequency, severity, and duration of mucositis. (Refer to the section on Oral Mucositis in this summary for more information.)
Mucositis pain may interfere with daily activities in approximately one-third of patients, interfering with social activities and mood in more than half. Mucosal pain may persist long after the mucositis resolves. Reports of mucosal sensitivity at 1-year follow-up are common, suggesting that chronic symptoms may be related to tissue change, including epithelial atrophy and/or neuropathy.
Orofacial pain after HNC therapy can be caused by musculoskeletal syndromes, including temporomandibular disorders associated with muscular fibrosis, scar formation, and discontinuity of the jaw. Ablative surgery may lead to tissue defects that may cause significant loss of orofacial function. Resection of the maxilla and mandible leads to sensory impairment, and more than half of patients experience regional hyperalgesia or allodynia. Pain scores after surgery for HNCs are highest for oral cavity cancers, followed by cancers of the larynx and oropharynx.