BACKGROUND Isolated unilateral
hypoglossal nerve injury is extremely rare. It may be caused by
radiation therapy targeting
neoplasms of the cephalic region. CASE REPORT A 51-year-old man with
synovial sarcoma of the left upper arm status post extensive
radiation therapy in 1980 presented in late 2014 with gradual onset of speech difficulty and difficulty moving his tongue for a couple of weeks. Neurological examination revealed isolated left-sided unilateral tongue
atrophy. Postradiation residual extensive
cicatrix with
erythema over the whole left upper extremity extending to the neck on the affected side was noticed. On head magnetic resonance imaging (MRI) before and after administration of
gadolinium, he was found to have asymmetrically fatty striations,
atrophy, and
fibrosis in the left tongue consistent with radiation toxicity. The patient's tongue weakness persisted without improvement. CONCLUSIONS The diagnosis of unilateral
hypoglossal nerve injury is usually difficult. Detailed neurological examinations and thorough investigations including head MRI are very helpful. Previous exposure to
radiation therapy is a potential cause of
hypoglossal nerve injury. To our knowledge, this is the first case report that presents isolated unilateral tongue
atrophy as a late complication of juxta cephalic
radiation therapy.