Brighina Filippo, Giglia Giuseppe, Scalia Simona, Francolini Margherita, Palermo Antonio, Fierro Brigida
Department of Neurology, Ophthalmology, Otology and Psychiatry, University of Palermo, Via G. La Loggia 1, 90129 Palermo, Italy.
Exp Brain Res. 2005 Feb;161(1):34-8. doi: 10.1007/s00221-004-2042-7. Epub 2004 Oct 12.
We previously showed paradoxical facilitatory effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) on striate and extrastriate cortex of patients suffering migraine with aura. In this study we evaluated the effects of 1 Hz rTMS on the excitability of inhibitory and facilitatory circuits of motor cortex to explore whether the abnormal pattern of excitability extends beyond the sensory cortex also involving motor areas in migraine with aura. Nine patients affected by migraine with aura and eight healthy controls entered into the study. The hot spot for activation of the right abductor pollicis brevis (APB) was checked by means of a figure-of-eight coil and motor threshold (MT) recorded on this point. Nine hundred magnetic stimuli at 1 Hz frequency and 90% MT intensity were delivered at the hot spot. Before and after rTMS, intracortical inhibitory and facilitatory circuit excitability was assessed by means of a paired pulse paradigm (conditioning stimulus 80% MT and test stimulus 120% MT) with two different interstimulus intervals: 2 ms (inhibitory) and 10 ms (facilitatory). Amplitude of the responses was expressed as the percentage of motor evoked potential (MEP) to test stimulus alone. Results showed that in basal condition migraineurs present significantly reduced levels of intracortical inhibition (ICI) compared to controls. More importantly, opposite results were obtained in migraineurs with respect to controls when 1 Hz rTMS was applied. Specifically, whereas intracortical facilitation (ICF) significantly decreased in controls, it significantly increased in migraineurs. ICI levels were not significantly affected by low-frequency stimulation. Our results showed that motor as well as sensory cortex of migraine patients present an abnormal modulation of cortical excitability, where a relevant role is likely played by the inefficiency of inhibitory circuits.
我们之前发现，低频重复经颅磁刺激（rTMS）对伴有先兆偏头痛患者的纹状皮质和纹状外皮质具有矛盾的促进作用。在本研究中，我们评估了1赫兹rTMS对运动皮质抑制性和易化性回路兴奋性的影响，以探究兴奋性异常模式是否不仅存在于感觉皮质，还涉及伴有先兆偏头痛患者的运动区域。9名伴有先兆偏头痛患者和8名健康对照者参与了本研究。使用8字形线圈检查右侧拇短展肌（APB）激活的热点，并记录该点的运动阈值（MT）。在热点处以1赫兹频率和90%MT强度施加900次磁刺激。在rTMS前后，通过配对脉冲范式（条件刺激为80%MT，测试刺激为120%MT），采用两种不同的刺激间隔：2毫秒（抑制性）和10毫秒（易化性），评估皮质内抑制性和易化性回路的兴奋性。反应幅度表示为单独对测试刺激的运动诱发电位（MEP）的百分比。结果显示，在基础状态下，与对照组相比偏头痛患者的皮质内抑制（ICI）水平显著降低。更重要的是，在应用1赫兹rTMS时，偏头痛患者与对照组获得了相反的结果。具体而言，对照组的皮质内易化（ICF）显著降低，而偏头痛患者的ICF显著增加。低频刺激对ICI水平没有显著影响。我们的结果表明，偏头痛患者的运动皮质和感觉皮质均存在皮质兴奋性的异常调节，其中抑制性回路效率低下可能发挥了重要作用。
