Estañol B, Sánchez-Munguia S, Corona Marco V, Elias Y, Téllez-Zenteno J F, García-Ramos G
Laboratory of Clinical Neurophysiology, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México.
Neurologia. 2003 Jul-Aug;18(6):303-9.
To determine the percentage of appearance of the H reflex and long latency reflexes (LLRs) in the thenar and hypothenar muscles of normal subjects to a fixed threshold mixed nerve electrical stimulus and variable degrees of muscle contraction.
Fifteen subjects aged 21 to 32 years of age without any prior history of central or peripheral neurological diseases volunteered for the study. The stimulation was a constant currrent given at the wrist with the cathode positioned proximally; started at 1 mA and it was gradually increased mA by mA until the M response appeared with the subject relaxed. The intensity of the stimulation was thereafter kept constant. The contraction was an abducting movement of the thumb in the case of the thenar muscle and abduction of the digiti minimi in the case of the hypothenar muscle and was sustained throughout the study. The reflexes were elicited with a repetition rate of 3 Hz, the stimulus was a square pulse of 0.5 ms. We used a low frequency pass filter of 10 Hz and a high frequency pass filter of 10 kHz. The sweep speed was set a 10 ms per division. The responses were averaged 200 times and then smoothed.
The mean intensity of the stimulus that evoked the H response, for all subjects, was 7.5 2.8 mA. The mean latency of the H reflex elicited with stimulation of the median nerve was 26 ms 2.03 ms (std. error 0.28, maximum 28.2, minimum 22.0). The mean latency of the H reflex elicited with stimulation of the ulnar nerve was 25.1 ms 1.64 ms (std. error 0.230, maximum 28, minimum 22.3). The difference between the percentage of responses attained under a relaxed condition and with any kind of muscle contraction was highly significant statistically using the Chi square method (p < 0.001). When we compared the percentage of the H responses obtained with slight, moderate, strong contraction, and contraction against resistance, between them, we did no find a significant difference. The LLRs appeared only in the trials with strong contraction.
The H reflexes and the LLRs of the thenar and hypothenar muscle were not obtained with threshold stimulation when these muscles were relaxed. With any degree of muscle contraction the H reflex in these muscles could be obtained in 94 percent of the trials. Maximal contraction and contraction against resistance were the best conditions to elicit long latency responses.
确定正常受试者在固定阈值混合神经电刺激及不同程度肌肉收缩情况下，大鱼际肌和小鱼际肌中H反射和长潜伏期反射（LLRs）出现的百分比。
15名年龄在21至32岁之间、无中枢或周围神经疾病病史的受试者自愿参与本研究。刺激为在手腕处给予的恒定电流，阴极位于近端；从1 mA开始，每次增加1 mA，直至受试者放松时出现M波反应。此后刺激强度保持恒定。对于大鱼际肌，收缩为拇指外展动作；对于小鱼际肌，收缩为小指外展动作，且在整个研究过程中持续进行。以3 Hz的重复频率诱发反射，刺激为0.5 ms的方波脉冲。我们使用了10 Hz的低频滤波器和10 kHz的高频滤波器。扫描速度设置为每格10 ms。反应平均200次后进行平滑处理。
所有受试者诱发H反射的平均刺激强度为7.5±2.8 mA。刺激正中神经诱发的H反射平均潜伏期为26±2.03 ms（标准误0.28，最大值28.2，最小值22.0）。刺激尺神经诱发的H反射平均潜伏期为25.1±1.64 ms（标准误0.230，最大值28，最小值22.3）。使用卡方检验，放松状态下和任何类型肌肉收缩时获得的反应百分比之间的差异具有高度统计学意义（p<0.001）。当我们比较轻度、中度、强烈收缩及抗阻收缩时获得的H反射百分比时，未发现显著差异。长潜伏期反射仅在强烈收缩试验中出现。
当这些肌肉放松时，阈值刺激无法引出大鱼际肌和小鱼际肌的H反射和长潜伏期反射。在任何程度的肌肉收缩情况下，94%的试验中均可引出这些肌肉的H反射。最大收缩和抗阻收缩是引出长潜伏期反应的最佳条件。
