前庭功能下降主要是由于患者的前庭及前庭周围的组织发生了器质性改变，从而出现平衡功能紊乱，常见于耳蜗前庭疾病以及神经中枢病变，而辐射造成前庭功能受损鲜有报道。本文报道了1例肺癌颅脑转移患者接受放射治疗（放疗）后前庭功能受损的案例。患者全脑放疗（总放射量70 Gy）结束2个月后出现头晕，行走不稳，前庭性共济失调，四肢乏力，进行性加重，伴耳鸣，听力下降。予改善微循环，并辅以前庭康复习服训练治疗后，随访5个月余，患者头晕症状较前有所改善，但姿势不稳仍存在。高剂量放射治疗（放疗）可使前庭毛细胞萎缩，前庭毛细血管发生脆性特发性改变，导致半规管囊斑和壶腹嵴的神经感觉上皮缺失，前庭毛细胞有髓神经纤维的丧失；产生较多氧自由基，氧自由基使毛细胞脂质过氧化或血管变性，微循环紊乱，破坏椭圆囊斑和球囊斑上支持细胞和毛细胞丢失；血管纹血管损伤，而导致患者前庭功能障碍。

The decrease of vestibular function is mainly due to the organic changes of vestibular and surrounding tissues, resulting in the disorder of balance function elements. It is commonly seen in cochlear vestibular diseases and nerve center lesions. However, vestibular function impairment caused by radiotherapy is rarely reported. This paper reports a case of vestibular function impairment after radiotherapy in a patient with brain metastasis of lung cancer, who developed dizziness 2 months after the completion of whole brain radiotherapy. The patient had walking instability, vestibular ataxia, limb weakness, and progressive aggravation, accompanied by tinnitus, hearing loss. With ameliorating microcirculation and vestibular rehabilitation training, the patient’s dizziness symptoms were improved while the postular instability continued to exist. High dose of radiation can make vestibular hair cells atrophy, vestibular capillary brittle idiopathic changes, resulting in the loss of semircular canalcysts and ampullae of nerve sensory epithelium, and vestibular hair cells may lose medullary nerve fibers. More oxygen free radicals, excessive oxygen free radicals during radiotherapy may cause hair cell lipid peroxidation or vascular degeneration, microcirculatory element disorder, damaging the elliptic cyst and balloon plaque supporting cells and hair loss of cells, vascular damage, and vestibular dysfunction.