Encyclopedia entry

Brain Stem

Published on 9 August 2026Version 1

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Abstract

Heterotopias of white matter within the medulla oblongata have been described. The left pyramid decussates first in about 73% of individuals. Interesting variations in the pyramidal tracts have been reported. In about 71% of 144 specimens, both crossed and uncrossed pyramidal tracts were present bilaterally. In 13%, only crossed tracts were present; in 12%, both crossed tracts and one uncrossed tract were present; in 2.8%, only uncrossed tracts were found; and in 0.7%, one pyramid was totally crossed, and the other pyramid was totally uncrossed.

Heterotopias of white matter within the medulla oblongata have been described.

The left pyramid decussates first in about 73% of individuals. Interesting variations in the pyramidal tracts have been reported. In about 71% of 144 specimens, both crossed and uncrossed pyramidal tracts were present bilaterally. In 13%, only crossed tracts were present; in 12%, both crossed tracts and one uncrossed tract were present; in 2.8%, only uncrossed tracts were found; and in 0.7%, one pyramid was totally crossed, and the other pyramid was totally uncrossed.

Riferimenti dell’opera originale

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Mikhael, M.A. and A.G. Mattar (1978) Malformation of the cerebral cortex with heterotopia of the gray matter. J. Comput. Assist. Tomogr. 2:291-296.
Mueller, C.F. (1970) Heterotopic gray matter. Radiology 94:357-358.
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Anatomical classification

Systems:: Nervous system

Content provenance

Adaptation

Adaptation of «Brain Stem — Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System» by Ronald A. Bergman, Adel K. Afifi, Ryosuke Miyauchi. Source: https://www.anatomyatlases.org/AnatomicVariants/NervousSystem/Text/BrainStem.shtml Original work distributed under the CC BY-NC-SA 4.0 licence (https://creativecommons.org/licenses/by-nc-sa/4.0/deed.it). Adaptation by Redazione AIVA. Changes from the original: Testo originale inglese riprodotto integralmente e riorganizzato nel formato scheda del portale (sintesi, testo, riferimenti), senza modificarne le affermazioni. La traduzione italiana non è ancora stata eseguita, e la pagina lo dichiara. Le figure non sono state copiate: sono collegate alla pagina d’origine. This publication is not approved or endorsed by the authors of the original work.

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