Serranová Teresa, Valls-Solé Josep, Muñoz Esteban, Genís David, Jech Robert, Seeman Pavel
Department of Neurology, 1st Medical Faculty, Charles University, Prague, Czech Republic.
Neurosci Lett. 2008 May 23;437(1):15-9. doi: 10.1016/j.neulet.2008.03.068. Epub 2008 Mar 28.
Central motor conduction time (CMCT) is usually abnormally prolonged in leg muscles of patients with pure hereditary spastic paraparesis (PHSP). One consequence of such abnormality should be an abnormal timing in the modulation of segmental reflexes, which might be more relevant for the pathophysiology of spasticity-related gait disturbances than just the CMCT delay. We examined the effects of transcranial magnetic stimulation (TMS) on the soleus H reflex in 13 control subjects and 11 PHSP patients using a conditioning (TMS) and test (H reflex) paradigm. Interstimulus interval (ISI) was 0-100 ms in steps of 10 ms. The amplitude of the H reflex at each interval was expressed as percentage of the control H reflex and the conditioned curves were compared between control subjects and patients. In control subjects, TMS-induced facilitation of the H reflex with two well-defined phases: early (ISIs 10 and 20 ms) and late (ISIs 70-90 ms). In patients, the early phase of facilitation was significantly reduced, while there was facilitation at 40 ms that was not present in control subjects. However, neither the characteristics of the MEP nor the differential modulation of the H reflex correlated significantly with clinical measures of motor dysfunction. Our results indicate an abnormal effect of TMS on the H reflex in PHSP patients. This suggests that the excitability of interneurons and soleus motoneurons is not modified in tune with the arrival of descending inputs. Desynchronization of the descending volley may contribute to both the lack of early facilitation and the presence of abnormal facilitatory phases.
在纯遗传性痉挛性截瘫（PHSP）患者的腿部肌肉中，中枢运动传导时间（CMCT）通常会异常延长。这种异常的一个后果应该是节段性反射调制的时间异常，这可能比单纯的CMCT延迟与痉挛相关步态障碍的病理生理学更相关。我们使用条件刺激（经颅磁刺激，TMS）和测试（H反射）范式，研究了13名对照受试者和11名PHSP患者中TMS对比目鱼肌H反射的影响。刺激间隔（ISI）以10毫秒的步长设置为0 - 100毫秒。每个间隔的H反射幅度表示为对照H反射的百分比，并比较对照受试者和患者之间的条件曲线。在对照受试者中，TMS诱导的H反射易化有两个明确的阶段：早期（ISI为10和20毫秒）和晚期（ISI为70 - 90毫秒）。在患者中，早期易化阶段明显减少，而在40毫秒时存在对照受试者中不存在的易化。然而，运动诱发电位（MEP）的特征和H反射的差异调制均与运动功能障碍的临床指标无显著相关性。我们的结果表明TMS对PHSP患者的H反射有异常影响。这表明中间神经元和比目鱼肌运动神经元的兴奋性没有随着下行输入的到来而同步改变。下行冲动的去同步化可能导致早期易化的缺乏和异常易化阶段的出现。
