Thompson P D
University Department of Medicine, Royal Adelaide Hospital, South Australia.
Clin Neurosci. 1995;3(4):203-8.
Myoclonus occurs in about 50% of cases of corticobasal degeneration. The myoclonus is focal, affecting one arm or less commonly a leg. Action and reflex myoclonus, induced by sensory stimulation of the affected limb, are characteristic. Accordingly, the myoclonus of corticobasal degeneration has many of the clinical characteristics of cortical myoclonus. In contrast to the recognized forms of cortical reflex myoclonus, the myoclonus of corticobasal degeneration is not associated with enlargement of the secondary component of the cortical somatosensory evoked potential (SEP) or backaveraged electroencephalographic (EEG) spikes preceding each myoclonic jerk. Furthermore, the latency of reflex myoclonus in corticobasal degeneration is some 10 ms shorter than that seen in cortical reflex myoclonus. One explanation for these differences may be the preferential enhancement of different components of long-latency transcortical reflexes in different diseases. Changes in the sensory input to the cortex, alterations in the balance of local cortical excitatory and inhibitory influences, and therefore cortical excitability are likely to be important factors in determining the physiological characteristics of myoclonus of cortical origin.
肌阵挛出现在约50%的皮质基底节变性病例中。肌阵挛为局灶性，累及一侧上肢，较少累及一侧下肢。由受累肢体的感觉刺激诱发的动作性和反射性肌阵挛是其特征。因此，皮质基底节变性的肌阵挛具有许多皮质性肌阵挛的临床特征。与公认的皮质反射性肌阵挛形式不同，皮质基底节变性的肌阵挛与皮质体感诱发电位（SEP）的继发性成分增大或每次肌阵挛发作前的反向平均脑电图（EEG）棘波无关。此外，皮质基底节变性中反射性肌阵挛的潜伏期比皮质反射性肌阵挛短约10毫秒。这些差异的一种解释可能是不同疾病中长潜伏期经皮质反射的不同成分优先增强。皮质感觉输入的变化、局部皮质兴奋性和抑制性影响平衡的改变以及因此导致的皮质兴奋性变化，可能是决定皮质源性肌阵挛生理特征的重要因素。
