Postirradiation vertigo in nasopharyngeal carcinoma survivors.

OBJECTIVE: Vertigo rarely manifested as an initial symptom of nasopharyngeal carcinoma or an early symptom after irradiation; however, increasing numbers of long-term nasopharyngeal carcinoma survivors experienced it. The purpose of this study was to investigate the causes of vertigo in irradiated nasopharyngeal carcinoma survivors.
SETTING: University hospital. PATIENTS: From January 1992 to December 2001, a total of 113 nasopharyngeal carcinoma patients (67 men and 46 women) with postirradiation vertigo consecutively visited our vertigo clinic. The mean interval from completion of irradiation to the occurrence of vertigo was 10 years. Each patient underwent otoscopic examination and a battery of audiovestibular function tests. Then, correlation between the vertigo and the radiation effect was explored.
RESULTS: Postirradiation vertigo was mainly attributable to peripheral labyrinthine disorder (69%), followed by central vestibular lesions (31%). The vertiginous and associated symptoms including severity, nausea/vomiting, oscillopsia, or imbalance in cases of peripheral labyrinthine disorder were milder than those in central vestibular lesion. Meanwhile, the former had less life impact and better response to therapy compared with the latter. The mean radiation dosage in both groups was 73 +/- 6 Gy and 74 +/- 5 Gy, respectively, without a significant difference. Of these 113 patients, 85 patients (75%) had radiation otitis media in one or both ears, and 28 patients disclosed bilateral intact eardrums. The prevalence of radiation otitis media in patients with postirradiated vertigo was 53% versus 73% for those with radiation dosage less than or more than 71 Gy, respectively, exhibiting a significant difference. However, the prevalence of radiation otitis media is unrelated to radiation interval. In comparison with absent caloric responses in radiation otitis media ears, 32% versus 57% in those of less than or more than 71 Gy, respectively, indicates a significant difference.
CONCLUSIONS: Vertigo is a late complication in irradiated nasopharyngeal carcinoma survivors, which is mainly caused by the sequela of radiation otitis media. Because the latter is correlated with the radiation dosage, 70 Gy is recommended as the maximum dosage for nasopharyngeal carcinoma. Eradicating radiation otitis media in nasopharyngeal carcinoma survivors may subsequently prevent the postirradiation vertigo.