Muellbacher W, Artner C, Mamoli B
Ludwig Boltzmann Institute for Epilepsy and Neuromuscular Disorders, Second Department of Neurology, Neurological Hospital of Vienna, Austria.
J Neurol Neurosurg Psychiatry. 1998 Nov;65(5):755-61. doi: 10.1136/jnnp.65.5.755.
The occurrence of a lingual paralysis after unilateral upper motor neuron lesions is an infrequent clinical phenomenon, and the underlying pathophysiological mechanisms are poorly understood. We studied the cortical motor representations of ipsilateral and contralateral lingual muscles in healthy controls and in a selected group of stroke patients, to clarify the variable occurrence of a lingual paralysis after recent monohemispheric ischaemia.
A special bipolar surface electrode was used to record the ipsilateral and contralateral compound muscle action potentials (CMAPs) from the lingual muscles after transcranial magnetic stimulation (TMS) of the human motor cortex and peripheral electrical stimulation (PES) of the hypoglossal nerve medial to the angle of the jaw. Four patients with a lingual paralysis (group 1) and four patients with symmetric lingual movements (group 2) after monohemispheric first ever stroke were studied and compared with 40 healthy controls.
In controls, TMS of either hemisphere invariably produces CAMPs in the ipsilateral and contralateral lingual muscles, elicited through crossed and uncrossed central motor pathways, respectively. In the 40 healthy controls, TMS of either hemisphere elicited CMAPs of significantly greater amplitudes and shorter onset latencies from the contralateral muscles compared with the ipsilateral responses (p<0.0001). In the patient groups, TMS of the affected hemisphere failed to evoke any CMAP from either lingual side; TMS of the unsevered hemisphere always produced normal ipsilateral and contralateral responses, irrespective of whether the ipsilateral muscles were paralysed or not.
Bilateral crossed and uncrossed corticonuclear projections are invariably existent in humans. After unilateral interruption of these pathways, some people do exhibit a lingual paralysis whereas others do not. The development of a central lingual paralysis is most likely dependent on the ability of the unsevered hemisphere to utilise the pre-existent uncrossed motor projections. The variable availability of these pathways among individual subjects is in good agreement with the inconstant occurrence of a lingual paralysis after restricted monohemispheric lesions.
单侧上运动神经元损伤后发生舌瘫是一种罕见的临床现象，其潜在的病理生理机制尚不清楚。我们研究了健康对照者和一组选定的中风患者同侧和对侧舌肌的皮质运动代表区，以阐明近期单半球缺血后舌瘫的不同发生率。
使用一种特殊的双极表面电极，在对人类运动皮质进行经颅磁刺激（TMS）以及对下颌角内侧的舌下神经进行外周电刺激（PES）后，记录舌肌的同侧和对侧复合肌肉动作电位（CMAP）。研究了首次发生单半球中风后出现舌瘫的4例患者（第1组）和舌运动对称的4例患者（第2组），并与40名健康对照者进行比较。
在对照者中，刺激任一半球的TMS均能分别通过交叉和不交叉的中枢运动通路，在同侧和对侧舌肌中诱发复合肌肉动作电位（CAMP）。在40名健康对照者中，与同侧反应相比，刺激任一半球的TMS从对侧肌肉诱发的CMAP振幅明显更大，起始潜伏期更短（p<0.0001）。在患者组中，刺激患侧半球未能从任一侧舌肌诱发任何CMAP；未受损半球的TMS总是产生正常的同侧和对侧反应，无论同侧肌肉是否瘫痪。
双侧交叉和不交叉的皮质核投射在人类中始终存在。这些通路单侧中断后，有些人确实会出现舌瘫，而另一些人则不会。中枢性舌瘫的发生很可能取决于未受损半球利用预先存在的不交叉运动投射的能力。这些通路在个体受试者中的可用性各不相同，这与局限性单半球损伤后舌瘫的不恒定发生情况高度一致。
