SUMMARY -Following a brief review of the concept of extrapyramidal system, clinical and anatomic evidence is presented against its relative prominence in man. It is proposed that the greatest part of those structures traditionally labeled as extrapyramidal effects its respective functional activities by way of the pyramidal tracts themselves.Such structures, centered around the basal nuclei, the cerebellum and possibly, the limbic areas of the prosencephalon are, according to the present suggestion, indeed, pre pyramidal. This model is based upon the clinical analysis of patients and agrees with more than one century of anatomic verifications in human brains, favoring the notion of the singularity of the human brain.
Hemiplegia motora e organização cerebral do movimento no homem: II. O mito do sistema extrapiramidal humanoRESUMO -Após revisão sumária do conceito de sistema extrapiramidal, são apresentadas evidências clínicas e anatômicas contra sua importância relativa no homem.Propõe-se que as estruturas tradicionalmente agrupadas sob o rótulo extrapiramidal efetuem a maior parte de suas atividades funcionais, respectivamente, por intermédio dos próprios feixes piramidais. Tais estruturas -centradas nos núcleos da base dos hemisférios cerebrais, no cerebelo e, possivelmente, também, nas áreas límbicas do prosencéfalo -, de acordo com nossa proposição são, na verdade pre-piramidais.Esse modelo se baseia na análise clínica de pacientes, está de acordo com mais de um século de verificações anatômicas em cérebros humanos e, depõe a favor da noção de singularidade do cérebro humano.Anatomical and functional reorganization in the human brain --Contrary to the pyramidal system concept 1^ which evolved in daily clinical practice, the concept of the 'extrapyramidal system' (EPS) was coined by Prus at a physiology laboratory in 18981-24.He investigated the means by which cortically induced epilepsy spread down to segmental levels.Working on dogs, Prus realized that the convulsions would not be affected by bilateral transections of the pyramidal tracts (PTs) at either mesencephalic or pontine levels, which led to the conclusion that epileptic volleys could be transmitted caudally through pathways distinct from the PTs. These, he proposed to call "extrapyramidal" It is noteworthy that Prus believed such EP pathways to follow a sequential multisynaptic course from the cerebral cortex to the spinal cord, due to a number of interruptions in subcortical and brainstem stations.He also suggested that such tracts would be responsible for the 'coordination and association' of movements. Contemporary studies have confirmed and extended Prus' views by showing the anatomical organization of the cortico-reticulospinal tracts 132 a n d their crucial role in the propagation of cortical epilepsy to the segmental apparatus 149} * Serviço de Neurologia (Prof. H. Alvarenga), Hospital Universitário Gaffrée e Guinle, Rio de Janeiro.
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