[Neurophysiology of parkinsonian syndromes].

Neurophysiological investigations may contribute to establish the diagnosis of different parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration, which are often suspected in case of atypical parkinsonian syndrome. They provide a means of objective analysis of certain symptoms (myoclonus for example) and identify the pathophysiological processes underlying these parkinsonian syndromes. This article reviews especially the following electrophysiological tests: autonomic nervous system analysis (sympathetic sudomotor skin response, R-R interval variation, electromyography of the external anal sphincter), surface electromyography and movement recording to investigate myoclonus, somatosensory and motor evoked potentials, brainstem reflexes (mainly the blink reflex), startle reaction, monosynaptic and long latency reflexes and finally the premotor potentials (contingent negative variation, Bereitschaftspotential) and movement-related desynchronization).