Tyvaert L, Cassim F, Derambure P, Defebvre L
Service de Neurophysiologie Clinique, EA 2683, IFR 114, Hôpital Roger Salengro, 59037 Lille Cedex.
Rev Neurol (Paris). 2007 Sep;163(8-9):779-91. doi: 10.1016/s0035-3787(07)91460-5.
Corticobasal degeneration (CBD) is a neurodegenerative disorder of mid- to late-adult life. From a clinical standpoint, CBD is characterized by (i) an insidious onset and a slowly progressing, unilateral, levodopa-unresponsive parkinsonian syndrome with dystonia or myoclonus and (ii) cerebral features such as apraxia, alien limb phenomena and cortical sensory loss. Decisive clinical diagnostic criteria are not available and thus a neuropathological study remains essential for accurate CBD diagnosis. Consequently, additional non-clinical criteria must be identified in order to improve diagnosis while patients are still alive.
Electrophysiological exploration can yield functional information on a number of brain structures (both cortical and sub-cortical) involved in CBD. The disorder features a specific cortical (frontoparietal) alteration which could help with differential diagnoses for other extrapyramidal syndromes. Hence, exploration of a patient's myoclonus can provide some specific arguments for CBD. Indeed, myoclonus displays a number of clinical and electromyographical characteristics which are consistent with a cortical origin (a shorter latency of the cortical C response, for example). However, some typical cortical features are missing (giant somesthesic evoked potentials, and cortical potentials preceding myoclonus in jerk-locked back-averaging studies). Some authors explain these abnormalities in terms of a sub-cortical origin for the myoclonus. The frontoparietal alteration in CBD has also been explored in studies of oculomotor movement. Indeed, asymmetric lengthening of the lateral ocular saccade latency argues more in favour of CBD than progressive supranuclear palsy. Moreover, cognitive function is also compromised in the early stages of CBD, although it is sometimes difficult to distinguish between CBD, PSP and frontotemporal dementia. Studying cognitive potentials enables one to confirm subcorticofrontal abnormalities and to dissociate CBD patterns from PSP patterns. Other electrophysiological tests (such as the exploration of dysautonomia, the palmomental reflex and the blink reflex) produce results which overlap with those seen in extrapyramidal syndromes and synucleinopathies (polysomnography), prompting discussion of the physiopathological mechanisms of these various diseases.
Electrophysiological exploration is of value for diagnosing CBD in general and for studying specific, frontoparietal dysfunctions in particular. These techniques could also significantly contribute to our understanding of the physiopathology of CBD.
皮质基底节变性（CBD）是一种发生于成年中期至晚期的神经退行性疾病。从临床角度来看，CBD的特征为：（i）起病隐匿，进展缓慢，单侧出现对左旋多巴无反应的帕金森综合征，并伴有肌张力障碍或肌阵挛；（ii）具有诸如失用症、异己肢体现象和皮质感觉丧失等脑部特征。目前尚无决定性的临床诊断标准，因此神经病理学研究对于准确诊断CBD仍然至关重要。因此，必须确定额外的非临床标准，以便在患者尚存活时改善诊断。
电生理检查可以获取有关CBD所涉及的多个脑结构（包括皮质和皮质下结构）的功能信息。该疾病具有特定的皮质（额顶叶）改变，这有助于对其他锥体外系综合征进行鉴别诊断。因此，对患者肌阵挛的检查可以为CBD提供一些特定的依据。实际上，肌阵挛表现出许多与皮质起源相符的临床和肌电图特征（例如，皮质C反应潜伏期较短）。然而，一些典型的皮质特征并不存在（巨大体感诱发电位，以及在抽动锁定反向平均研究中肌阵挛之前的皮质电位）。一些作者用肌阵挛的皮质下起源来解释这些异常。在眼球运动研究中也对CBD的额顶叶改变进行了探索。实际上，外侧眼扫视潜伏期的不对称延长更支持CBD而非进行性核上性麻痹。此外，在CBD的早期阶段认知功能也会受到损害，尽管有时很难区分CBD、进行性核上性麻痹和额颞叶痴呆。研究认知电位能够证实皮质下额叶异常，并将CBD模式与进行性核上性麻痹模式区分开来。其他电生理检查（如自主神经功能障碍检查、掌颏反射和瞬目反射）产生的结果与锥体外系综合征和突触核蛋白病（多导睡眠图）中所见结果重叠，这引发了对这些各种疾病病理生理机制的讨论。
电生理检查总体上对诊断CBD具有价值，尤其对于研究特定的额顶叶功能障碍具有重要意义。这些技术也可能极大地有助于我们对CBD病理生理学的理解。
