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Comparative-Anatomical Studies en the Motor Nucleus and the Mesencephalic Nucleus of the Trigeminal Nerve

1959; Volume: 18; Issue: 1 Linguagem: Inglês

10.1679/aohc1950.18.107

0004-0681

Yuzo Akasaka,

Trigeminal Neuralgia and Treatments

1. In this study, PAL-carminestained serial transverse sections of the brains of man, 14 other Primates, 2 Prosimiae, 17 Carnivora, 11 Ungulata, 3 Cetacea, 6 Rodentia, 4 Chiroptera, 3 Insectivora, 9 Edentata, 9 Marsupialia, 4 Monotremata (83 species of Mammalia in total), a cock and a hen, 6 Reptilia and a frog were used as materials.2. The absolute number of cells in the motor trigeminal nucleus showed nearly no difference in its right and left halves.3. The relative development of the motor trigeminal nucleus as indicated by the ratio of the number of cells in the nucleus to the cross-sectional area of the brain stem was the highest in Prosimiae, Rodentia and Chiroptera, mediocre in Primates, Fissipedia, Insectivora and Marsupialia, and the lowest in man, Pinnipedia, Cetacea, Edentata (except three-toed sloth) and Monotremata. It was found high in my bird, reptile and frog specimens.4. The development of the motor trigeminal nucleus depends not only on the quantitative development of the masticatory muscles due to the feeding habit of the animals, but also on the modality of the movement of the muscles differing in accordance with the differences in the mobility of the mandibular joint and the origin and the insertion of the muscles.5. The absolute number of cells in the mesencephalic trigeminal nucleus is not different in its right and left halves. The relative number of cells in this nucleus changes in parallel relation with that in the motor trigeminal nucleus, suggesting the close correlation between the two nuclei.6. The largest majority of the cells of the mesencephalic trigeminal nucleus are found in the alar plate, i.e., the sensory zone, only a very few being found in the basal plate and none in Monotremata and the classes of Aves and below. The cells in the alar plate tend to aggregate the more to the dorsal median, the lower the animal in the scale of evolution.7. From the above findings, it is inferred that the mesencephalic trigeminal nucleus is of sensory nature and is closely correlated with the motor trigeminal nucleus, that is, is concerned with the proprioceptive sensation of the masticatory muscles.8. KAPPERS has quoted his so-called neurobiotaxis theory in explaining the relative positions of the two trigeminal nuclei, but the results of my quantitative study based on numerous specimens of brains of many species of animals showed clearly that his theory is not at all tenable.