Objective: The study aimed to investigate whether sample sizes of F-wave study differed according to different nerves, different F-wave parameters, and amyotrophic lateral sclerosis(ALS) patients or healthy subjects. Methods: The F-waves in the median, ulnar, tibial, and deep peroneal nerves of 55 amyotrophic lateral sclerosis (ALS) patients and 52 healthy subjects were studied to assess the effect of sample size on the accuracy of measurements of the following F-wave parameters: F-wave minimum latency, maximum latency, mean latency, F-wave persistence, F-wave chronodispersion, mean and maximum F-wave amplitude. A hundred stimuli were used in F-wave study. The values obtained from 100 stimuli were considered "true" values and were compared with the corresponding values from smaller samples of 20, 40, 60 and 80 stimuli. F-wave parameters obtained from different sample sizes were compared between the ALS patients and the normal controls. Results: Significant differences were not detected with samples above 60 stimuli for chronodispersion in all four nerves in normal participants. Significant differences were not detected with samples above 40 stimuli for maximum F-wave amplitude in median, ulnar and tibial nerves in normal participants. When comparing ALS patients and normal controls, significant differences were detected in the maximum (median nerve, Z=-3.560, P<0.01; ulnar nerve, t=5.019, P<0.01; tibial nerve, Z=-2.475, P<0.05; peroneal nerve, Z=-2.088, P<0.05)and mean F-wave latency (median nerve, Z=-3.243, P<0.01; ulnar nerve, t=3.876, P<0.01; tibial nerve, Z=-2.206, P<0.05; peroneal nerve, Z=-2.205, P<0.05)in all four nerves, F-wave chronodispersion (Z=-3.152, P<0.01)in the ulnar nerve, F-wave persistence in the median (Z=6.139, P<0.01)and ulnar nerves(Z=5.350, P<0.01), mean F-wave amplitude in the tibial nerve(t=2.981, P<0.01), maximum F-wave amplitude in the ulnar (Z=-2.134, P<0.05)and tibial nerves (t=2.746, P<0.01)with 20 stimuli; for chronodispersion in tibial nerve (t=2.551, P<0.05)100 stimuli, for chronodispersion in peroneal nerve (Z=-2.086, P<0.05)80 stimuli, for F-wave persistence in tibial nerve (Z=2.119, P<0.05) 60 stimuli, for mean F-wave amplitude in ulnar (Z=-2.552, P<0.05)and peroneal nerve (Z=-2.228, P<0.05)40 stimuli, for maximum F-wave amplitude in peroneal nerve (t=2.693, P<0.01)60 stimuli were necessary to detect differences. Conclusions: Sample sizes of F-wave study differed according to different nerves, different F-wave parameters , and ALS patients or healthy subjects.
目的： 本研究旨在探讨不同神经﹑不同F波参数以及正常或疾病状态下F波参数所需刺激次数是否存在差异。 方法： 对2013年8月至2014年7月就诊于北京协和医院神经科的55例肌萎缩侧索硬化(ALS)患者和52名健康受试者进行正中神经﹑尺神经﹑胫神经和腓神经F波检测，使用的刺激次数为100次。分析的F波参数包括最短﹑最长和平均F波潜伏期，F波出现率，F波时间离散度，平均和最大F波波幅。从100次刺激获得的F波参数认为是正常参考值。比较从前20次﹑40次﹑60次和80次刺激获得的F波参数与正常参考值的差异；比较不同刺激次数下ALS患者与健康受试者F波各参数的差异。 结果： 健康受试者4条所检神经≥ 60次刺激所获时间离散度与正常参考值差异无统计学意义；正中神经﹑尺神经和胫神经≥ 40次刺激所获最大F波波幅与正常参考值差异无统计学意义。与健康受试者相比，20次刺激可以发现ALS患者四条所检神经最长(正中神经Z＝－3.560，P<0.01；尺神经t＝5.019，P<0.01；胫神经Z＝－2.475，P<0.05；腓神经Z＝－2.088，P<0.05)和平均F波潜伏期(正中神经Z＝－3.243，P<0.01；尺神经t＝3.876，P<0.01；胫神经Z＝－2.206，P<0.05；腓神经Z＝－2.205，P<0.05)，尺神经时间离散度(Z＝－3.152，P<0.01)，正中神经(Z＝6.139，P<0.01)和尺神经(Z＝5.350，P<0.01)F波出现率，胫神经平均F波波幅(t＝2.981，P<0.01)，尺神经(Z＝－2.134，P<0.05)和胫神经(t＝2.746，P<0.01)最大F波波幅与健康受试者差异有统计学意义；胫神经(t＝2.551，P<0.05)需要100次刺激，腓神经(Z＝－2.086，P<0.05)需要至少80次刺激可发现ALS患者时间离散度显著延长；胫神经(Z＝2.119，P<0.05)需要至少60次刺激可以发现ALS患者F波出现率显著降低；尺神经(Z＝－2.552，P<0.05)和腓神经(Z＝－2.228，P<0.05)需要至少40次刺激可以发现ALS患者平均F波波幅显著升高；腓神经(t＝2.693，P<0.01)需要至少60次刺激可以发现ALS患者最大F波波幅显著升高。 结论： 不同神经﹑不同F波参数和正常或ALS患者所需的F波刺激次数不同。.
Keywords: Amplitude; Amyotrophic lateral sclerosis; F-waves; Latency; Persistence.