[Isolated hypoglossal nerve paralysis: a case report].

Cranial nerve paralysis is an uncommon complication of radiotherapy for head and neck carcinomas because cranial nerves are relatively resistant to radiation. The incidence of this complication has been declared to be 1-5% in different studies. Unlike the other cranial nerves, isolated hypoglossal nerve paralysis in patients who have been treated with radiotherapy for nasopharyngeal carcinomas is a worrisome sign of recurrence. We report a 45-year-old male patient admitted to our clinics with complaints of difficulty in moving his tongue and dysphasia five years after combined radiotherapy and chemotherapy for nasopharyngeal carcinoma. Recurrence of the tumor was thought to be the cause of the isolated hypoglossal nerve paralysis at first, however late toxicity of radiotherapy was found to be the etiological factor after detailed examinations.