Some Interesting Facts

Assessment of head and neck pain is challenging in cancer patients due to its multifactorial etiology and its modification during treatment . We discuss the etiology of pain, diagnostic approach and current therapeutic issues.

Head and neck cancer accounts for 5 to 10% of malignant tumors and pain is a presenting symptom in 20% of patients having tumors of the oral cavity.

Pain is also experienced by 40 to 80 % of patients suffering from head and neck cancer

The cure of tumors of the head and neck region is only 35%

Etiology of Pain of Head and Neck Cancer

Most patients with advanced head and neck cancers have more than one cause of pain.

Causes of pain include:

• Pain caused by cancer(compression or infiltration of pain sensitive structures) .
• Pain caused by treatment (consequence of radiotherapy, surgery or chemotherapy).
• Pain associated with debilitating disease (postherpetic neuralgia or bedsores). 
• Pain unrelated to cancer or treatment (arthritis ,migraine or neuropathy).

The majority of pain is caused by cancer (83%) and /or secondary effects of oncological therapy (28%).

The assessment of the type and the cause of pain is important because the first indicates the appropriate symptomatic therapy and the latter the appropriate treatment of the underlying disease.

Nociceptive pain is caused by stimulation of the free nerve endings (peripheral nociceptors belonging to A-delta and C-fibers).As a result of this stimulation action potentials are transmitted to the central nervous system and perceived as pain.

Nociceptive pain is subdivided into actual nociceptive pain,nociceptive nerve pain or referred pain.Nociceptive pain is diagnosed as pain of new onset and is linked to active tissue damage by tumor occurrence, tumor associated inflammation ,ischemia,trauma (not necessarily cancer related) or subclinical or neural infection.

Nociceptive nerve pain is diagnosed as pain of slow onset that was localized in the sensory distribution of one of the cranial nerves,peripheral nerves or nerve roots innervating the skull ,face or shoulder and has an established cause of active tissue damage such as tumor recurrence or benign inflammation. Referred pain is diagnosed as pain of new onset without local cause at the site of pain.Active tissue damage is present in pharynx, hypopharynx,esophagus, trachea or mediastinum supposedly stimulating sympathetic nerve endings and leading to pain in the corresponding region of the face of the skull.

Methods in evaluating Head and Neck Cancer

Typically a patient is referred to the Pain Management Center by the primary care provider.

An initial questionnaire is administered including information about the quality and intensity of the pain.

Then a history is elicited, noting not only the location, severity, and characteristics of the pain but also the events surrounding the initial pain period as well as the past medical and surgical therapies.

A physical examination is performed, followed by a psychological interview. Social work interviews are used to identify the action of family and environmental factors that contribute to pain.

Often patient is instructed to keep a pain diary and finally appropriate consultations are arranged as needed.

The pain assessment should consist of a number of components including:

1. Evaluation of the patients’ perception of pain and the meaning of pain for him or her.
2. Evaluation of the physical, emotional, cognitive and behavioral responses that occur with pain.
3. Evaluation of the impact of pain on different aspects of the significant others.
4. Responses of significant others.
5. Coping strategies employed and
6. Evaluation of the descriptive characteristics of the pain such as location, intensity, quality, and chronology of the pain experience and treatment.

In addition to determining the frequency and severity of pain the questionnaire must be used as part of the assessment of interventions planned to manage oral pain.

The physical examination and diagnostic assessment involves inspection of the skin, oral cavity, nose, paranasal sinuses, naso -oro and hypopharynx, larynx and thyroid gland.

Pain Treatment

Treatment of pain of head and neck cancer is multifactorial and includes:

• outpatient and inpatient drug therapy
• neuroablation, nerve blocks
• electrical stimulation
• physical therapy
• psychological techniques
• For the treatment of mild pain aspirin ,acetaminophen or NSAIDS are generally recommended.The liquid form of acetylsalicylic acid trisalicylate (500 mg/5ml) is useful.The side effects can be avoided by using a buffered form or an enteric- coated formula.
• The NSAIDS have been shown to be effective analgesics or coanalgesics when there is evidence of bone involvement. Any NSAIDS must be used cautiously in elderly patients and in patients with renal insufficiency,heart failure, hypertension or history of peptic ulcer disease.The maximum dose should not exceed 1.5 to two times the usual recommended starting dose.
• The minimum period necessary to determine their efficacy is generally 2 to 3 weeks.If there is no benefit it is reasonable to change drugs because patient may respond poorly to one medication and well to another. This is because of the different chemical classes of nonsteroidal medications. If there is no relief from a nonnarcotic agent, codeine is the first narcotic drug given. It is a weak analgesic and can be combined with acetaminophen or aspirin.
• Patients with severe pain should be treated with an opioid. Morphine remains the prototypic opioid agonist analgesic.  A reasonable starting dose of liquid is 5-10 mg every 4 hours around the clock. Most of the patients achieve control of their pain at dosages of up to 30 mg on this schedule. However there is no upper dose limit. For individuals unable to take liquid morphine, suppositories are an appropriate alternative. Sustained-release morphine can be given every 8 to 12 hours. It is first necessary to titrate the dose of one of the usual short-acting morphine agents. Once a stable state is reached, one can switch to sustained-release products divided into two equal doses every 12 hours.
• Head and neck cancer patients usually have increasing analgesic requirements because of tumor progression. Administration of breakthrough regimens are commonly coadministered. Because NSAIDS work in the periphery and narcotics mostly in the CNS the combination can be efficacious.
• While originally listed as weak opioid, as a single agent, oxycodone has no ceiling effect and possesses the activity and properties of a strong opioid.

Methadone is useful for patients who do not tolerate morphine. Methadone shows peculiar pharmacokinetics and has a long half life. Plasma levels do not correlate with analgesic efficacy and the doses should be escalated cautiously. Concurrent use of barbiturates reduces the effectiveness of methadone. A combination of methadone and psychostimulants, such as d-Amphetamine, may provide analgesia without excess sedation and perhaps, with a heightened sense of energy and well - being for some patients with chronic head pain.

Neuropathic (deafferentation )pain, like bone pain is common in advanced head and neck cancer and does not usually respond well to opioids alone. The addition of anticonvulsants, or orally administered antiarrhythmics to the opioid regiment is often efficacious.

Corticosteroids, especially dextromethasone and methylprednisolone, have several uses as adjuvants. They provide an initial euphoriant effect, tend to stimulate appetite, are antinflammatory and ameliorate hypercalcemia.

Tricycle antidepressants, especially Amitriptiline, have an analgesic effect independent of their antidepressant activity. The concomitant antidepressant effects and improved sleep may all enhance the patient’s feeling of well being.

Transdermal fentanyl it is a safe and good alternative therapy to conventional strong opioids. Adjuvants ,such as laxatives, antiemetics, H-2 receptor antagonists ,antacids ,antipsychotics (to treat emesis,anxiolytics or hypnotics are prescribed to ameliorate coexisting symptoms or side effects of analgesic treatment. Transcutaneous Electrical Nerve Stimulation (TENS) is a unique mode of pain therapy that is essentially free of systemic effects. It has been applied in cases with myofacial pain ,postherpetic neuralgia and autonomic hyperreflexia.

Occipital nerve block is the treatment for occipital headaches which are sometimes the manifestation of basal skull invasion. Myofacial pain often is present in the area of the sternocleidomastoid or trapezius especially after radical neck dissection and can be improved with trigger point injections. Superficial cervical plexus block has good results for alleviating pain in postradical neck dissection syndrome which usually occurs few days after surgery and most commonly is manifested as pain in C2, C3 distribution. Chemical or radiofrequency neurolysis has been used for lesions involving the trigeminal ganglion or its branches. Neurolysis has also been used for the glossopharyngeal nerve or the sphenopalatine ganglion.

Intraventricular morphine(IVM) administration has been used to manage head and neck pain and diffuse pain caused by advanced metastatic cancer. Intraventricular morphine is a useful and generally safe method for the control of intractable end -stage pain.

IVM administration seems to be a simple and safe method for palliation of intractable pain. Satisfactory results can be obtained in the majority of patients with low (<1 mg) daily doses of morphine with mild to moderate toxicity. The more serious complications seems to be respiratory depression which is more frequent with intrathecal than with Intraventricular administration.

Nevertheless the method is invasive and should be considered only after failure or limitation of lumbar intrathecal administration. Percutaneous stereotactic radiofrequency (RF) lesions of afferent nerves, ascending tracts in the brainstem or thalamic nuclei have successfully relieved pain in the majority of cancer patients who underwent such operations.

Conclusion

Assessment of the type and cause of the pain in head and neck cancer helps to define proper therapy. Successful pain management requires treatment of all aspects of pain: Physical, psychological and social. Although good pain relief is achieved in many patients with severe pain, using symptomatic therapy, successive attempts in treating pain are usually needed utilizing pharmacological, interventional and psychological modalities.