Torres F, Hutton J T
Neurol Clin. 1986 May;4(2):369-86.
The role of EEG in the study of the dementias is to help in the differential diagnosis of the multiple causes of this syndrome. EEG is useful in differentiating early on between treatable and as of now untreatable forms of dementia. Space-occupying lesions that give rise to dementia are reliably detected by EEG. Infectious, toxic, and metabolic processes are associated with early and severe electroencephalographic abnormalities. The "slow virus" infections show characteristic electrical patterns that reliably distinguish them from the cortical or subcortical dementias. Finally, the EEG may contribute to distinguishing between Alzheimer's disease and MID, two commonly occurring forms of dementia. The paucity of substantial early EEG abnormalities in Alzheimer's disease, although helping to differentiate it from other dementias, leaves us without a currently available physiologic test that provides positive evidence for this condition. Recent studies of EPs, however, suggest that some intermediate latency VEP components may be delayed in patients with Alzheimer's disease when compared with normal subjects. This is encouraging, as latencies in VEPs are more reliable and less variable than amplitude that has previously been reported as "abnormal" in some early Alzheimer patients. Long latency ERPs and CNV also show early abnormalities in Alzheimer's disease. Tests of eye movements such as ERPs are psychophysiologic tests requiring some degree of patient cooperation. Performance on tests of ocular smooth pursuit correlate highly with severity of the dementia syndrome in Alzheimer's disease. In contrast, smooth pursuit testing is usually normal in elderly patients with pseudodementia of depression, suggesting this test may be of some value in differentiating these two clinical disorders. Some evidence exists that smooth pursuit eye movements are also normal, at least in the early and middle stages, in Pick's disease, again suggesting that eye movement testing may prove to have some utility in differentiating this form of dementia from Alzheimer's disease. Ocular scanpaths are abnormal in dementia. They typically are poorly organized and at times perseveratory. In addition, the average durations of eye fixations during directed visual search are altered in dementia as compared with normals. The average eye fixation durations are longer with Alzheimer's disease and briefer in patients with frontal lobe tumors as compared with elderly normal controls. These group differences suggest differing scanning strategies for these two forms of dementia.(ABSTRACT TRUNCATED AT 400 WORDS)
脑电图在痴呆症研究中的作用是帮助对该综合征的多种病因进行鉴别诊断。脑电图有助于早期区分可治疗和目前无法治疗的痴呆症形式。脑电图能够可靠地检测出导致痴呆症的占位性病变。感染性、中毒性和代谢性过程与早期严重的脑电图异常有关。“慢病毒”感染呈现出特征性的电活动模式，可将其与皮质性或皮质下痴呆可靠地区分开来。最后，脑电图可能有助于区分阿尔茨海默病和多发梗死性痴呆这两种常见的痴呆症形式。阿尔茨海默病早期脑电图明显异常较少，这虽有助于将其与其他痴呆症区分开来，但目前尚无一项生理检查能为该病提供阳性证据。然而，近期的事件相关电位研究表明，与正常受试者相比，阿尔茨海默病患者的一些中间潜伏期视觉诱发电位成分可能延迟。这令人鼓舞，因为视觉诱发电位的潜伏期比先前报道的某些早期阿尔茨海默病患者“异常”的波幅更可靠且变异性更小。长潜伏期事件相关电位和关联性负变在阿尔茨海默病中也显示出早期异常。像事件相关电位这样的眼动测试是需要患者一定程度配合的心理生理测试。在阿尔茨海默病中，眼球平稳跟踪测试的表现与痴呆综合征的严重程度高度相关。相比之下，患有抑郁性假性痴呆的老年患者的平稳跟踪测试通常正常，这表明该测试在区分这两种临床病症方面可能具有一定价值。有证据表明，至少在早期和中期，匹克病患者的平稳跟踪眼动也是正常的，这再次表明眼动测试可能在将这种痴呆症形式与阿尔茨海默病区分开来方面具有一定作用。痴呆症患者的眼球扫描轨迹异常。它们通常组织不佳，有时还会持续。此外，与正常人相比，痴呆症患者在定向视觉搜索过程中眼球注视的平均持续时间会发生改变。与老年正常对照组相比，阿尔茨海默病患者的平均眼球注视持续时间更长，而额叶肿瘤患者的则更短。这些组间差异表明这两种痴呆症形式的扫描策略不同。（摘要截选至400词）
