Ziemann U, Paulus W, Rothenberger A
Department of Clinical Neurophysiology, University of Göttingen, Germany.
Am J Psychiatry. 1997 Sep;154(9):1277-84. doi: 10.1176/ajp.154.9.1277.
Fluctuating motor and vocal tics are the diagnostic feature of Tourette's disorder. The pathophysiology of tics is still unclear. One major hypothesis is a deficient inhibitory control through the cortical-striatal-thalamic-cortical motor loop. The authors tested this hypothesis by investigating motor cortex excitability through use of the technique of transcranial magnetic stimulation.
Twenty patients with Tourette's disorder and a comparison group of 21 healthy subjects were studied. Focal transcranial magnetic stimulation was applied to the left motor cortex, and surface electromyography (EMG) was recorded from the right abductor digiti minimi muscle. As measures of motor cortex excitability, motor threshold, cortical silent period, and intracortical inhibition and facilitation were studied. The peripheral silent period and the maximum M wave after supramaximal electrical stimulation of the ulnar nerve at the wrist were also determined.
Motor threshold and peripheral motor excitability were normal in the Tourette's disorder group, but the cortical silent period was shortened and the intracortical inhibition reduced. A subgroup analysis of the patients with Tourette's disorder revealed that these abnormalities were seen mainly when tics were present in the EMG target muscle or in patients without neuroleptic treatment. Age, sex, attention deficit hyperactivity disorder, obsessive-compulsive disorder, and sensory urges had no significant effect on motor excitability.
Findings are consistent with the hypothesis that tics in Tourette's disorder originate either from a primarily subcortical disorder affecting the motor cortex through disinhibited afferent signals or from impaired inhibition directly at the level of the motor cortex or both.
运动和发声抽动的波动是抽动秽语综合征的诊断特征。抽动的病理生理学仍不清楚。一个主要假说是通过皮质-纹状体-丘脑-皮质运动环路的抑制控制不足。作者通过使用经颅磁刺激技术研究运动皮质兴奋性来检验这一假说。
对20例抽动秽语综合征患者和21名健康对照者进行研究。将局灶性经颅磁刺激应用于左侧运动皮质，并记录右侧小指展肌的表面肌电图（EMG）。作为运动皮质兴奋性的指标，研究了运动阈值、皮质静息期以及皮质内抑制和易化。还测定了外周静息期以及腕部尺神经超最大电刺激后的最大M波。
抽动秽语综合征组的运动阈值和外周运动兴奋性正常，但皮质静息期缩短，皮质内抑制降低。对抽动秽语综合征患者的亚组分析显示，这些异常主要出现在EMG目标肌肉出现抽动时或未接受抗精神病药物治疗的患者中。年龄、性别、注意缺陷多动障碍、强迫症和感觉冲动对运动兴奋性无显著影响。
研究结果与以下假说一致，即抽动秽语综合征中的抽动要么源于主要影响运动皮质的皮质下疾病，通过传入信号去抑制作用，要么源于运动皮质水平直接的抑制受损，或者两者兼而有之。
