鼻咽癌放疗后视野与视觉诱发电位的改变

背景与目的:放射治疗是鼻咽癌患者的主要治疗方法,随着放疗后患者生存期的延长,放射治疗的并发症也逐渐增多,其中放射性视神经损伤越来越受到人们的重视。本研究通过视野和视觉诱发电位(visual evoked potential,VEP)检查研究放射性视神经损伤并探讨损伤发生的部位。方法:对28例行单纯根治性放疗的鼻咽癌患者在放疗前、放疗结束、放疗后5年内进行视野和VEP检查。结果:28例患者中有21例共34眼(60.7%)出现各种病理性视野,44.1%的病理性视野发生在放疗后10～24个月。病理性视野的类型分别为:8眼出现向心性视野缩小,6眼为双侧颞侧偏盲,8眼局部光敏度下降,10眼有中心性暗点或旁中心暗点,2眼出现生理性盲点扩大。有26例患者共44眼(78.6%)出现VEP异常,54.5%VEP异常发生在放疗后14个月以内。放疗后1年内与放疗前相比,大、中、小方格VEP的潜伏期延长,差异有统计学意义(P<0.001,P<0.001,P=0.001);振幅降低,但差异无统计学意义(P=0.249,P=0.940,P=0.450)。放疗1年后,大、中、小方格VEP的潜伏期比放疗前延长(P=0.004,P<0.001,P<0.001),振幅降低,大、小方格振幅的变化有统计学意义(P=0.002,P=0.189,P<0.001)。VEP病理性视野的发生与放疗剂量的大小有关,照射总剂量DT>70Gy组与DT≤70Gy组病理性视野发生率的差异有显著

Changes of visual field and visual evoked potential in nasopharyngeal carcinoma patients after radiotherapy

BACKGROUND & OBJECTIVE: Radiotherapy is the main treatment for nasopharyngeal carcinoma (NPC). The incidence of radiation-induced complications, especially radiation optic neuropathy (RON), increases along with prolonging survival time of the patients. This study was to investigate RON in NPC patients after irradiation by visual field and visual evoked potential (VEP) tests. METHODS: A total of 28 NPC patients, who underwent conventional external-beam irradiation, received visual field and VEP tests before irradiation, at the end of irradiation, and 5 years after irradiation. RESULTS: Thirty-four (60.7%) eyes in 21 patients developed pathological visual field; 15 (44.1%) of these 34 eyes occurred within 10-24 months after irradiation. Of the 34 eyes, 8 showed concentric visual field constriction; 6 showed bitemporal hemianopia; 8 showed local photosensitivity descend; 10 showed central or cecocentral scotoma; 2 showed scotoma enlargement. Forty-four (78.6%) eyes in 26 patients appeared VEP abnormity; 24 (54.5%) of these 44 eyes occurred within 14 months after irradiation. In small, medium, and large elements, VEP latencies were significantly longer within 1 year after irradiation than pre-irradiation (P < 0.001, P < 0.001, and P=0.001); VEP amplitudes were lower within 1 year after irradiation than pre-irradiation without significant difference (P=0.249, P=0.940, and P=0.450). One year after treatment, VEP latency delay maintained in each element (P=0.004, P < 0.001, P < 0.001); VEP amplitudes were decreased (P=0.002, P=0.189, P < 0.001). The incidence of pathologic visual field was significantly lower in patients received irradiation of < or =70 Gy than in patients received irradiation of > 70 Gy (50.0% vs. 77.3%, P=0.041). CONCLUSIONS: RON correlates to total irradiation dose. Pathologic visual field may indicate the position of RON.