Issac Thomas Gregor, Chandra S R, Nagaraju B C
Department of Neurology, Neurocentre, NIMHANS, Bangalore, Karnataka, India.
Ann Indian Acad Neurol. 2013 Oct;16(4):619-22. doi: 10.4103/0972-2327.120493.
The diagnostic accuracy of the currently available tools carries poor sensitivity resulting in significant delay in specific diagnosis of cortical dementias. Considering the properties of default mode networking of the brain it is highly probable that specific changes may be seen in frontotemporal dementias (FTDs) and Alzheimer's disease sufficiently early.
The aim of this study is to look for changes in Transcranial Magnetic Stimulation (TMS) in cortical dementia.
Evaluated with a single pulse TMS with the figure of eight coil and recorded from right first dorsal interossei (FDI). Resting Motor Threshold (RMT) was estimated on the opposite motor cortex (T1). Second site of stimulation was cervical spine at C7-T2. Central motor conduction time (CMCT) is equal toT1-T2. Silent Period (SP) identified by applying TMS pulse to contracting FDI.
RMT was reduced in seven out of eight Alzheimer's dementias. CMCT was in the upper limit of normal in both patients with FTD. The most consistent observation was that SP was reduced and there were escape discharges noticed during the SP suggesting increased cortical excitability and decreased cortical inhibition. This suggests probable early asymptomatic changes in the gamma-aminobutyric acid (GABA) nergic and cholinergic system is taking place. This if confirmed may give some insight into early diagnosis and therapeutic role of GABA agonists in these disorders.
目前可用工具的诊断准确性敏感性较差，导致皮质性痴呆的特异性诊断出现显著延迟。考虑到大脑默认模式网络的特性，额颞叶痴呆（FTD）和阿尔茨海默病很可能会在足够早的阶段出现特定变化。
本研究旨在寻找皮质性痴呆经颅磁刺激（TMS）的变化。
使用八字形线圈进行单脉冲TMS评估，并从右侧第一背侧骨间肌（FDI）记录。在对侧运动皮层（T1）估计静息运动阈值（RMT）。第二个刺激部位是C7 - T2水平的颈椎。中枢运动传导时间（CMCT）等于T1 - T2。通过对收缩的FDI施加TMS脉冲来确定静息期（SP）。
8例阿尔茨海默病痴呆患者中有7例RMT降低。FTD患者的CMCT均在正常上限。最一致的观察结果是SP缩短，且在SP期间出现逃逸放电，提示皮质兴奋性增加和皮质抑制降低。这表明γ-氨基丁酸（GABA）能和胆碱能系统可能正在发生早期无症状变化。如果得到证实，这可能会为这些疾病的早期诊断以及GABA激动剂的治疗作用提供一些见解。
