Hayes K C, Allatt R D, Wolfe D L, Kasai T, Hsieh J
Department of Physical Medicine and Rehabilitation, Parkwood Hospital, London, Ont., Canada.
Electroencephalogr Clin Neurophysiol. 1992 Apr;85(2):102-9. doi: 10.1016/0168-5597(92)90075-m.
A 20 msec train (500 Hz; 0.1-0.2 msec duration) of percutaneous electrical stimulation (ES) applied to the plantar surface was used to condition muscle responses evoked in tibialis anterior (TA) by transcranial magnetic stimulation of the motor cortex in 8 subjects with traumatic spinal cord injury (SCI). The intensity of conditioning ES was adjusted to just subthreshold for evoking flexion reflexes in TA and was delivered at conditioning-test (C-T) intervals of 15-60 msec prior to cortical stimulation. Four subjects with clinically complete SCI revealed no muscle response to cortical stimulation or following combined subliminal percutaneous ES and cortical stimulation. Four subjects (3 clinically incomplete and 1 complete injury) demonstrated muscle responses with a latency of 70-80 msec time-locked to the percutaneous ES when the conditioning subliminal stimulation was delivered at C-T: 15-40 msec. These responses, resembling suprathreshold flexion reflexes, reflect the convergence of excitatory afferent and cortical inputs and provide evidence of preserved corticospinal innervation to the L4-5 segmental motoneuron or interneuron pools. In 3 of the subjects this preserved corticospinal influence was evident despite absence of motor evoked potentials (MEPs) following cortical stimulation. The effect of the combined electrical and cortical stimulation in yielding suprathreshold flexion reflexes, instead of the facilitated MEPs seen in control subjects, appears to be related to slowed central conduction, prolonged temporal dispersion of the motoneuron facilitation following cortical stimulation and segmental reflex changes associated with disrupted modulation of interneuronal pathways. The results show this conditioning paradigm to be useful in revealing preserved corticospinal innervation in some SCI subjects with absent MEPs.
对8名创伤性脊髓损伤（SCI）患者，采用经皮电刺激（ES）施加于足底表面，给予20毫秒的刺激串（500赫兹；持续时间0.1 - 0.2毫秒），以调节经颅磁刺激运动皮层在胫前肌（TA）诱发的肌肉反应。调节条件性ES的强度，使其刚好低于在TA中诱发屈曲反射的阈值，并在皮层刺激前15 - 60毫秒的条件 - 测试（C - T）间隔时施加。4名临床完全性SCI患者对皮层刺激或联合阈下经皮ES与皮层刺激均无肌肉反应。4名患者（3名临床不完全性损伤和1名完全性损伤）在C - T为15 - 40毫秒时给予阈下条件性刺激，表现出与经皮ES时间锁定的潜伏期为70 - 80毫秒的肌肉反应。这些类似阈上屈曲反射的反应，反映了兴奋性传入和皮层输入的汇聚，并提供了L4 - 5节段运动神经元或中间神经元池保留皮质脊髓神经支配的证据。在3名患者中，尽管皮层刺激后没有运动诱发电位（MEP），但这种保留的皮质脊髓影响仍然明显。联合电刺激和皮层刺激产生阈上屈曲反射的效果，而非对照受试者中所见的MEP易化，似乎与中枢传导减慢、皮层刺激后运动神经元易化的时间离散延长以及与中间神经元通路调制中断相关的节段反射变化有关。结果表明，这种条件化范式有助于揭示一些无MEP的SCI患者中保留的皮质脊髓神经支配。
