Private Health Hospital, Özel Ege Sağlık Hastanesi, Alsancak, Izmir, Turkey; Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Qld, Australia; and Departments of Neurology and Clinical Neurophysiology, Medical Faculty, Ege University, Izmir, Turkey.
Neuromodulation. 2010 Jul;13(3):232-7. doi: 10.1111/j.1525-1403.2010.00285.x.
The excitability of sensorimotor cortex and spinal motoneurones can be modulated by afferent signals arising from the periphery. Low- and high-frequency vibrations activate separate classes of afferent units in the periphery. Low-frequency vibrations (2-100 Hz) activate the type I fast adapting afferent units (FA-I), whereas high-frequency vibrations (60-1000 Hz) preferentially activate the type II units (FA-II). Muscle spindles are also sensitive to high-frequency mechanical vibrations. Motor-evoked potentials (MEP) generated in response to transcranial magnetic stimulation (TMS) can be modulated by afferent signals. However, it is not clear whether these interactions take place at cortical or spinal cord levels.
Cerebrovascular attacks resulting in stroke generally affect both sensory and motor systems. In eight stroke patients with partial motor deficit in the first two weeks of the incident we studies the effects of low- (30 Hz) and high- (130 Hz) frequency mechanical vibrations on the MEPs obtained in response to TMS. Recordings from the abductor digiti minimi muscle were carried out by TMS of both lesioned and intact hemispheres. Six patients were tested again four to eight weeks after the initial assessment. The results also were compared with data obtained from eight control subjects. MEPs were evoked by 50% above threshold intensities and for each testing condition initially five control MEPs were recorded. This was followed by consecutive MEPs obtained during vibration (N= 5) and between vibrations (N= 5), and the traces were averaged and analyzed.
In normal subjects both low- (30 Hz) and high- (130 Hz) frequency vibration resulted in shortening of MEP latencies. In patients, there was a similar effect on the affected side with 30 Hz, but not with 130 Hz. Stimulation of the intact hemisphere during high-frequency vibration in the second test revealed a latency shortening, which could be due to central reorganization. The amplitude of MEPs showed a stronger facilitation in the presence of low-frequency vibration in the early stage of stroke compared with normal subjects. However, in the second test the level of facilitation was reduced, indicating an effect at the cortical level.
The results suggest that a cerebrovascular accident influences the modulatory effects of afferent inputs at both spinal and cortical levels, and in time, as reorganization takes place, these altered influences settle towards normal levels.
感觉运动皮层和脊髓运动神经元的兴奋性可以通过来自外周的传入信号进行调节。低频和高频振动激活外周的不同类别的传入单位。低频振动（2-100 Hz）激活 I 型快速适应传入单位（FA-I），而高频振动（60-1000 Hz）优先激活 II 型单位（FA-II）。肌梭也对高频机械振动敏感。经颅磁刺激（TMS）产生的运动诱发电位（MEP）可以通过传入信号进行调节。然而，尚不清楚这些相互作用是发生在皮质还是脊髓水平。
导致中风的脑血管事件通常会同时影响感觉和运动系统。在 8 名中风患者中，在事件发生的前两周内，他们的运动功能仅出现部分缺损，我们研究了低频（30 Hz）和高频（130 Hz）机械振动对 TMS 产生的 MEP 的影响。通过对病变半球和未损伤半球的 TMS 记录拇短展肌的肌电图。6 例患者在初次评估后 4-8 周再次接受检查。结果还与 8 名对照受试者的数据进行了比较。MEP 是通过 50%以上的阈上强度诱发的，对于每种测试条件，最初记录 5 个对照 MEP。接下来是在振动期间（N=5）和两次振动之间（N=5）连续记录 MEP，并对轨迹进行平均和分析。
在正常受试者中，低频（30 Hz）和高频（130 Hz）振动均导致 MEP 潜伏期缩短。在患者中，30 Hz 对患侧有类似的影响，但 130 Hz 则没有。在第二次测试中，高频振动期间对未损伤半球的刺激显示出潜伏期缩短，这可能是由于中枢重组所致。与正常受试者相比，中风早期低频振动可使 MEP 振幅表现出更强的易化作用。然而，在第二次测试中，易化程度降低，表明这是皮质水平的影响。
结果表明，脑血管事件会影响传入输入在脊髓和皮质水平的调节作用，并且随着时间的推移，随着重组的发生，这些改变的影响会趋于正常水平。
