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Resume Introduction Certains cas d’hemiplegies associent l’elevation involontaire du bras paralyse au deroulement du bâillement. Patients et methode Quatre patients presentant ce mouvement, rarement decrit parce que sans doute le plus souvent neglige, ont ete examines. Leurs descriptions sont comparees a celles anterieurement publiees depuis 150 ans dans la litterature. L’imagerie cerebrale montre une lesion situee le plus souvent au niveau de la capsule interne. Par comparaison a des modeles experimentaux chez le chat, il est propose que la section de la voie cortico-neocerebelleuse du systeme extra-pyramidal libere le fonctionnement de la voie spino-archeocerebelleuse, permettant une stimulation motrice du bras a partir du noyau reticulaire lateral qui associe la rythmicite ventilatoire et la motricite. Resultats et conclusion Phylogenetiquement plus anciennes, des structures sous-corticales desinhibees, retrouvent une autonomie au cours d’un processus d’homeostasie associant l’ample inspiration du bâillement, comportement d’allure reflexe de stimulation de la vigilance, et la motricite du bras comme elle se remarque lors de la marche. Nous avons baptise ce phenomene parakinesie brachiale oscitante.

In some cases of hemiplegia the onset of yawning is associated with an involuntary raising of the paralyzed arm.Four observations of this movement, which is seldom described probably because it is mostly neglected, were made in the neurology unit of the University Hospital of Poitiers. The descriptions were compared with other cases that have been published in the medical literature of the last 150 years. Cerebral imagery shows a lesion that is most often localized on the internal capsule. After comparison with experimental models in cats, it is proposed that the section of the cortico-neocerebellum tract of the extra-pyramidal system disinhibits the spino-archeocerebellum tract, enabling a motor stimulation of the arm by the lateral reticular nucleus, which harmonises central respiratory and locomotor rhythms.Some subcortical structures, that are phylogenetically more ancient, thus disinhibit regained autonomy in the homeostasis process associating the massive inspiration of yawning--a form of reflex behavior that stimulates vigilance--with a motor control that is active during locomotion. For this phenomenon we coined the term "parakinesia brachialis oscitans".

Initially, basal ganglia was a descriptive term for onto- and phylogenetic or topographic classifications. A variable list of structures were included as basal ganglia. A major step was made when the thalamus was separated from the "striated bodies" (Vic d'Azyr, 1786) which was sometimes taken into account in the French description of the noyaux gris centraux. Even if the term is not perfect, it is preferable to "the system of basal ganglia". The subdivisions of the putamen, the distinction between the striatum and the pallidum were not really made until the beginning of the twentieth century. Modern tracing methods were needed to demonstrate the main connections. It was not until the end of the 1960s that the importance of the striato-pallido-nigral network within the basal ganglia and the cortico-striatal connections, the main afferent system, were recognized. With the description of the cortico-striatal connections, the sub-cortical system with multiple complex "loops" was questioned. The term "extra-pyramidal system" had an exaggerated success. Initially, it designated descending non-pyramidal afferents (some which do not exist) and their source. In 1992, Spatz based his separation of this heterogeneous group on the iron content. The terms of extra-pyramidal "system" and "syndrome" should be abandoned by clinicians. Physiological interpretations have varied. The role of automatic "habitual" motricity, derived from a concept of hierarchic, Jacksonian cerebral organization, was questioned when the pyramidal network was described. Clinico-pathological analysis (hemiballism, Parkinson's disease ...) has placed new emphasis on the motor role, for a time the only role accepted as real. More recently, debate has centred on other roles, particularly in cognition and motivation. An illustration of functions other than purely motor functions of the basal ganglia is given by the syndromes of loss of psychic auto-activation secondary to bilateral lesions.

The authors report the clinical and pathological findings in a 46 years old woman with Huntington's chorea and cerebello-olivar atrophy. Eight previously reported cerebellar atrophies in Huntington's chorea with pathological examination are reviewed. The primary or secondary nature of the cerebellar lesions is discussed.

The cortical origin of the pyramidal tract is first considered. Contributions of retrograde degeneration studies as well as fiber counting method following different cortical lesions are presented and discussed. The results of these classical neuro-anatomical methods are compared with those of the more recent retrograde transport tracing method. The number and the diameter spectrum of pyramidal tract fibers differ in various mammals. In more evolved species the number of pyramidal fibers increase and their diameter span becomes wider. The thickest fibers are found in man. Along their diencephalic, mesencephalic, pontine and medullary course, axonal collaterals of corticospinal axons may terminate onto cells of origin of other descending pathways, onto relay cells of ascending pathways, and onto neurons projecting to the cerebellum. At the spinal level, the rostrocaudal extent and the termination area of corticospinal fibers may differ in various mammals. In a first group of mammals, the corticospinal fibers extend only to cervical or mid-thoracic segments and terminate in the dorsal horn. In a second group of mammals, the corticospinal fibers extend throughout the spinal cord and terminate in the dorsal horn and the intermediate zone. In a third group of mammals, the corticospinal fibers extend throughout the spinal cord and terminate in the dorsal horn, the intermediate zone and the dorsolateral part of the lateral motoneuronal cell group. In a fourth group of mammals, the corticospinal fibers also extend throughout the spinal cord and terminate in the dorsal horn, the intermediate zone and the dorsolateral as well as the ventral parts of the lateral motoneuronal cell group. A comparison is made between these different types of spinal terminations and the motor capacities of these different species. The motor deficits observed after pyramidal lesions are summarized and a comparison is made between the corticospinal tract and the descending brain stem pathways. According to electrophysiological studies in conscious animals different pyramidal units can be activated during different types of movements and at different times during the preparation or execution of a movement. Recent neuro-anatomical data suggest that the pyramidal tract is composed of many structural subsystems. Recent physiological data suggest that the pyramidal tract can be involved in various aspects of the motor control.