Familial Nasopharyngeal Carcinoma 6

Long-Term Complication in the Treatment of Nasopharyngeal Carcinoma 285hyalinization and obliteration of the vasonervorumto the brachial plexus after radiation. All findingsindicated focal compression of the nerve by fibrosisor chronic nerve ischemia as the causes of neuropathy(Stoll et al. 1966).25.5.2.1Latent Period of CNPIt was reported that the median interval betweencompletion of radiotherapy and occurrence of neurologicsymptoms was 1–4 years (Stoll et al. 1966;Powell et al. 1990), although the symptoms of neuropathycould be progressive after many years posttreatment(Johansson et al. 2000, 2002).The results of the above-mentioned cross-sectionalstudy revealed that the median time to occurrence ofCNP was 8 years, and the incidence of the onset of cranialneuropathy within 5 years, between 5 to 10 years,10–15 years, and 15–20 years postradiation variedbetween 10% and 14%, without substantial differences(Kong and Lu et al. 2009, unpublished data). Therefore,late onset of radiation-induced peripheral neuropathyafter 15 years is not uncommon, and the probabilityremains constant for a considerable portion of thepatients’ life after the completion of radiation. This isof special relevance when the overall treatment outcomefor cancer patients improves, and the long-termsurvival becomes prevailing.Once developed, peripheral neuropathy maysteadily progress or stabilize, and only few patientsexperience improvement (Kong and Lu et al. 2009,Pierce et al. 1992; Harper et al. 1989; Salner et al.1981).at least 6–12 months after the onset of cranial nervepalsy to allow the stabilization of the symptoms.Although neurolysis or neurolysis with omentalgrafting aimed to relief fibrosis of epi- and perineuriumhas been reported to be effective in somepatients with brachial plexopathy (LeQuang 1989;Killer and Hess 1990), such a procedure is usuallynot feasible in the case of nasopharyngeal cancer dueto the critical location of most cranial nerves.Radiation-induced neuropathy in the anteriorgroup of cranial nerves is more likely to be caused bydirect damage from radiotherapy. Unfortunately, noproven effective treatment for radiation-inducednerve damage is available. Limited data supportedthe use of hyperbaric oxygen (HBO) and steroids forsymptomatic control in the acute phase of radiationinducedcranial neuropathy; however, no effectivelong-term control has been demonstrated with anytype of therapeutic efforts (Mihalcea and Arnold2008; Boschetti et al. 2006; Levy and Miller2006).As no effective treatment is available for radiation-inducedperipheral nerve damage, efforts shouldbe directed at preventative measures. Reduction inradiation field size and fraction size has been demonstratedto reduce late complication severity(Stinson et al. 1991). The utilization of IMRT in thetreatment of NPC requires delineation of a numberof neurological OARs including optic nerve, opticalchiasm, and cochlea. Limiting dose to nerves mayhelp in reducing the probability of cranial neuropathy.However, for patients with locally advanced NPC,especially T4 lesions, irradiating the cranial nervesinvolved or in proximity to the primary tumor areusually unavoidable.22.5.3ManagementUnderstanding of the cause of peripheral neuropathyis important for the proper treatment of cranial nervepalsy induced by high-dose irradiation. Radiationinducedposterior cranial neuropathy and brachialplexopathy are proven to be associated with musclefibrosis of the neck after radiation. Thus, symptomaticalleviation of muscle fibrosis by surgical interventionfor releasing cranial nerve from entrapmentcould be therapeutic (Lin et al. 2002; Hoeller et al.2004; Bowen et al. 1996; Fathers et al. 2002). Surgicalintervention for posterior cranial neuropathy causedby cervical muscle fibrosis should be postponed for22.6Brainstem and Spinal Cord Injury(Encephalomyelopathy)Because of the pattern of tumor invasion, the clivusfrequently receives a high dose of radiation duringradiotherapy for nasopharyngeal cancer. Given theproximity of the clivus to the brainstem and uppercervical spinal cord, those two structures are at riskof radiation-induced injury. In cases of extensiveposterior skull base involvement, the risk of injuryto the brain stem and cervical spinal cord is furtherelevated. Brainstem and spinal cord injury is themost devastating complication from head and neck