Vestibular apparatus disorders after external radiation therapy for head and neck cancers.

External irradiation of different head and neck cancers may involve parts of the ear. The vestibular function of 25 patients in which the inner ear was comprised in the irradiated volume was investigated by electronystagmography (ENG). Doses administered to the vestibular system ranged between 2800 and 5120 cGy. Five patients suffered subjective vertigo or dizziness. Eleven patients (three out of five with vertigo) showed vestibular abnormalities to ENG (44% of the total). Altered responses to specific tests were as follow: six patients to the bithermal caloric stimulation, two to the pendular-sinusoidal test and the other three to both of them. Patients were evaluated 3 and 6 months after the ending of the radiation therapy course. At the first evaluation, abnormalities to caloric test were noted in three patients (12%) and to sinusoidal rotatory test in one patient (4%). At the second evaluation, rates of abnormal response increased to 36% and 20%, respectively. Vestibular disorders seemed to be scantly related to the total radiation dose. Data of literature are discussed in order to identify possible implications on treatment planning.