The Tohoku Journal of Experimental Medicine, Vol. 57, No. 4, 1953 Studies on Brain Stem ‡W. Centering on Fazial Nucleus of Anencephalus By Shigeaki Yamamoto and Mariko Komatsu (山 本 重 亮) (小松 満 利子) (From the Anatomical Laboratory of Prof. H. Seto, Faculty of Medicine, Tohoku University, Sendai) (Received for publication, August 25, 1952) INTRODUCTION Many instances have been reported on anencephali, all of whom died within a very.short time after birth, though lucky enough to survive the parturition, except one case reported by Edinger and Fischer,1) which lived for a longer period of three and a half years. When an anencephalus lives after birth, be it for a short span, its actions and reactions can be minutely observed during its life-time, and a post-mortem microscopical examination of its central nervous system will furnish a very interesting material for the study of the paths and nuclei of the central nervous, system. An embryonic anencephalus is also material of study not far behind an infant anencephalus in scientific interest. One of the authors of this report, Yamamoto,2), 3) previously reported on his phylogenetic study in No. ‡U of this series of studies on brain stem, with brains of many kinds of mammalia as materials, and in No. ‡V of the same series, he used brains of human embryoes from 2 to 10 months of age, in an ontogenetic study, to examine the applicability of the famous neurobiotaxis theory by Kappers,4) with reference to the facial nucleus in main. In his above studies, he reported, as has been published in this journal, that he found the neurobiotaxis theory hardly befitting the ob served facts. We hereunder intend to reexamine the neurobiotaxis theory in its application, using the brain of an anencephalus as material. According to the neurobiotaxis theory, the nuclei of the cranial nerves, especially, the motor nuclei, are locally transferred due to the neurobiotaxis, during their phylogenetic and ontogenetic development. For example, the facial nucleus, originally situated more cranio-dorsally, is primarily drawn to the caudal from the cranial side by the stimulus. exerted " neurobiotaxically " by the solitary tract, and secondarily to. the ventral side from a more dorsal position by the strong stimulus from 359 360 S. Yamamoto and A komatsu the developing pyramidal tract, so that the facial nucleus, originally situated more cranio-dorsally, comes to occupy a markedly ventro-caudal position. Kappers and Vogt5) assert that the neurobiotaxis theory holds good also by anencephali. According to them, when the cerebral he mispheres are utterly absent, the pyramidal tract is also lacking entirely or at most present in only the barest rudiment, so that the facial nucleus is much displaced to the dorsal side from the normal position. However , Toyofuku6) has found that the position of the facial nucleus was normal, regardless of the degree of the development of the pyramidal tract, as the result of his study on four brains which had their pyramidal tract either in aplastic or agenetic development. Mrs. Bien7) of the same in stitute has reported on an interesting study of a malformed guinea-pig. This animal had two brains, the right-side brain of which was nearly perfectly developed, but in the left one, the cerebrum and diencephalon were entirely absent and only a trace of the midbrain was perceptible, the parts from the pons downward being in the relative proportion cor responding to normalcy. The two brains were studied in comparisoni but no discrepancy from the normal in the position of the facial nuclei was observed in both. Thus, she asserts, the position of the facial nuclei was wholly independent of the development of the pyramidal tract . So, both Toyofuku and Mrs. Bien are not in sympathy with the neurobiotaxis theory . Divergent views have been propounded on the positions of facial nuclei in anencephali who are utterly unprovided with pyramidal tracts. In the following report, we undertake to set forth our results of obser vations centering on the position of the facial nucleus, as based on the examination of one anencephalic brain, and simultaneously touch on the problem of the validity of the neurobiotaxis theory. EXPERIMENTAL Materials The material used belonged to a ten month human embryo , in which the cerebrum and diencephalon were lacking , and only the parts of the midbrain lower than the inferior colliculus inclusive were found remaining , with only an extremely limited quantity of nerve elements . The relation corresponding to the normal begins to assert itself as far down as the pons . The cerebellum is partially rather well-developed but the other part forms the so-called area cerebro-vasculosa. We studied this material in a series of transverse section preparations, stained with Pal-carmine . Findings with Discussion Most scholars on the subject deny the presence of pyramidal tracts Centeting on Facial Nuclcusof Anencephalus 361 in brains utterly destitute of cerebral hemispheres. Schwalbe8) and Zingerle9) contend that no fibre system can develop, if the seat of the cells of origin, the part concerned of the brain, does not exist, and on this score, deny the existence of pyramidal tracts in anencephali. In the case studied by Edinger and Fischer1) also the presence of pyramidal tract is negated. On the other hand, Arnold10) asserts that, though the tract is not visible macroscopically, on microscopical observation, small fibres thereof are always found to exist, so that anenccphalic brains even are not utterly destitute of pyramidal tracts. Fig. 1. Transversal section of medulla oblongata of anencephalus (10 month human embryo), Pal-carmine staining, low power view. Pyramid P is entirely undeveloped. O olive; Nh nucl. of hypoglossal nerve; h hy poglossal nerve; Ni nucl. intercalatus; Nv dorsal nucl. of vagus; S solitary tract; v vagus nerve; R restiform body; Spt spinal tract of trigeminal nerve; Lm medial lemniscus. In our case, as shown in Fig. 1, the olive is considerably well-developed, but the pyramid is entirely undeveloped, the spot appearing concave. In the interior, the medial lemniscus can be clearly traced, though in feeble development, reaching the ventral border of the medulla oblongata, and no trace of pyramidal tract is detected. In collating Fig. 1 with a picture of the corresponding part of a normal 10 month embryo (Fig. 2), it may be seen that the development of fibre system is weak in general, and that the pyramidal tract is entirely lacking. Fig. 3 and Fig. 4 show the incipient and best developed parts of the pons respectively and no trace of pyramidal tract is observable here. In the spinal cord the lateral funiculus where the lateral pyramidal tract should be located is narrower than in normal cases, the nerve elements in the area of the absent pyramidal tract are indistinct and look light throughout, giving a gelatinous ap 362 S. Yamamoto and M. Komatsu Fig. 2. Transversal section of medulla oblongata of normal 10 month human embryo, Pal-carmine staining, low power view. In general, all nerve elements are far better developed than anencephalus. P good developed pyramid; Pt pyramidal tract; Lm medial lemniscus; h hypoglossal nerve. Fig. 3. Transversal section of pons of anencephalus (10 month human embryo), Pal-carmine staining, low power view. No trace of pyramidal tract can be seen. F facial nucleus; T trapezoid body; a abducens nerve. Fig. 4. Transversal section of pons of anencephalus (10 month human embryo), Pal-carmine staining, low power view. No trace. of pyramidal tract can be seen and medial lemniscus Lm is weakly developed. F facial nucleus; f facial nerve; g genu of facial nerve; Na abducens nucleus; a abducens nerve; T trapezoid body; ac acoustic nerve. Centering on Facial Nucleus of Anencephalus 363 pearance. Of special interest is the fact that, in the cervical segments, the lateral funiculi are depressed inwardly, toward the place where the pyramidal tract should be located (Fig. 5). That a groove is formed in the direction toward the area where the lateral pyramidal tract should be, in anencephali, has been pointed out by Zingerle9) in one of his cases Fig. 5. Transversal section of cervical segment of spinal cord of anence phalus (10 month human embryo),. Pal-carmine staining, low power view. At lateral funiculus groove formation gr can be seen. Fig. 6. Transversal section of pons of normal 10 month human embryo, Pal-carmine staining, low power view. Collating with Fig. 4, basilar part of pons is better developed and bundle of pyramidal tract Pt. can be seen. wherein, he reports, the groove is extended to. the inferior parts of the thoracic segments. But in another of his cases, the groove was entirely lacking. Thus, the formation of grooves is not necessarily universal to all spinal cords of anencephali, but this frequent formation is presumably related with the absence or extremely feeble development of the pyramidal tract. The misdevelopment of the pyramidal tract seems to cause not only an abnormal narrowness of the lateral funiculus, but also the for mation of grooves due to the physical depression of the surface by the weakened interior resistence. Now, in our case, in spite of the nearly entire absence of the pyramidal tract, the facial nucleus is located at the very position corresponding to normalcy, as shown in Fig. 3. In normal brains, the nucleus is found 364 S. Yamamoto and M. Komatsu just above in close vicinity of the trapezoid body, and also in. our, an encephalus, the location is wholly analogous, no swerving toward the dorsal side being perceptible. However, on approaching the cranial extreme from Fig. 3 to Fig. 4, at the latter level the facial nucleus is seen to the side of the dorsal.