Biographies de neurologues
Nouvelle Iconographie de La Salpêtrière
 L'histoire des neurosciences à La Pitié et à La Salpêtrière J Poirier
The history of neurosciences at La Pitié and La Salpêtrière J Poirier 

mise à jour du
27 juillet 2008
Henry Kimpton Ed
p 754-756
Trophic nerves
R. Wyburn-Mason


Bulbar Structures Concerned in Primitive Movements
Certain deductions may be made about the various structures in the bulb and hypothalamus concerned in primitive movements. The pig mented cells of the substantia nigra and reticular formation of the pons and medulla function as vital centres controlling respiratory activity.
The connections of the substantia nigra in primates resemble those in the lower mammals. The nucleus receives afferents from the tectum, globus pallidus, corpus Luysii, lateral lemniscus and the mammillary bodies and both discharges into the reticular formation of the pons and medulla in relation to the dorsal nucleus of the vagus and also into the red nucleus. Trough the afferents from the tectum respiratory activity may be correlated with the primitive movements mediated through the tectal region, in which lies the centre for reflex vocalisation. Through the fibres it receives in the lateral lemniscus respiratory activity is correlated with reflex movments to sound.
Through the fibres from the mammifiary body the cells of the nucleus receive their controlling adrenergic fibres. Through the fibres from the globus pallidus and corpus Luysii respiratory activity may be correlated with other activities mediated by these two nuclei. Swallowing movements are dependent on structures beneath the floor of the fourth ventricle in the region of the vagus nucleus and stimulation in this region simultaneously causes swallowing and inhibits respiratory movements (Millet and Sherrington 1915-6).
Presumably involuntary opening of the mouth and chewing movements also depend on the integrity of the same area. It seems that the movements must depend on the local reticular structures. The afferent fibres concerned in this complex reflex reach this part of the bulb in the trigeminal, glossopharyngeal and vagus nerves.
Yawning still occurs after bilateral motor decortication in man or in decorticate lower mammals. In the former it is completely uncontrollable, as it may be in normal subjects. Yawning not only involves a wide opening of the mouth, but is preceded by a deep inspiration. The eyes often close and the act is often followed by pilo-erection and shivering. In biteral motor decorticate man yawning is accompanied by gross moves of the large joints (associated movements).
Curious attacks of yawning and respiratory disturbance may follow an attack of encephalitis lethargica, which especially damages the hypothalamus and the region of the substantia nigra. Yawning would thus appear to depend on the structures in the bulb or hypothalamus and to be closely related respiratory activity.
It occurs :
(1) In states of tiredness and sleepiness, in which there is a depression of adrenergic and an increase of trophic cholinergic activity throughout the brain.
(2) In conditions of excessive heat, when there is a general increase of cholinergic activity in the body and sleepiness.
(3) During anxiety, when a similar general stimulation of trophic and autonomic functions occurs.
(4) During the induction of amesthesia with barbituates, which depress adrenergic activity and induce sleep.
(5) In animals in states of anaphylactic shock, when the initial stimulation of all trophic and autonomie is followed by a depression of adrenergic activity.
(6) During boredom, when adrenergic activity is deficient.
Yawning thus occurs when there is a general increase of trophic cholinergic activity within the nervous system and thus when respiratory activity is diminished and anoxia tends to develop. Since general stimulation of adrenergic activity in the body increases the depth of respiration, the deep inspiration which precedes a yawn, and the pilo-erection and shivering, which follow indicate an increased adrenergic activity. This seems to be an attempt to increase the oxygenation of the blood by stimulation of the respiratory centres. The excitation of the structures in the reticular formation initiated by the activity of the substantia nigra apparently spreads to neighbouring nuclei and induces opening of the jaws and the primitive slight movements of the large joints occurring in bilateral motor decorticate man.
Le syndrome de Wyburn-Mason ou de Bonnet-Dechaume-Blanc comprend l'association de malformations artério-veineuses du maxillaire, de la rétine, du nerf optique, du thalamus, de l'hypothalamus et du cortex cérébral. La prévalence du syndrome n'est pas connue mais il est très rare : moins de 100 cas ont été publiés à ce jour.
Wyburn-Mason syndrome is characterized by the association of arteriovenous malformations with a metameric topography located in the facial and ocular-orbital regions or involving the central nervous system. The syndrome is very rare with about 100 cases reported in the literature so far.