Paper - A human foetus exhibiting iniencephaly and other abnormalities (1922)
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Hayes WI. A human foetus exhibiting iniencephaly and other abnormalities. (1922) J Anat. 56: 155-159. PMID 17103942
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A human foetus exhibiting iniencephaly and other abnormalities
By William Ivon Hayes, M.B. (Melbourne), Trinity College, Dublin.
"Turovcs the kindness of the Master of the Rotunda Hospital, Dublin, I was permitted to examine the unusual foetus here described. I am unable to find any previous record of a similar foetus having occurred in the practice of the hospital, and certainly none such has been seen there within the last ten years.
Fig. 1. Camera lucida drawing of foetus,
Fig. 2. Camera lucida drawing of foetus, from right side, from front.
The foetus is full time. The hair is about half an inch long on the head, the nails project just beyond the finger tips and unusually large centres of ossification are present at the lower end of the femur, and the upper end of the tibia.
The head is slightly enlarged, measuring 38 cms. in greatest circumference, and the face looks slightly upwards. Owing to the increase in size of the vault of the skull, the ears, which are both somewhat deformed, seem to be set more anteriorly than normal. The head is imperfectly separated from the body by an ill-defined neck, so that the contour of the head is almost directly continuous with that of the body. The abdomen is protuberant, with the umbilicus looking downwards, while the back, between the occiput and the nates, is greatly decreased in length. The combined length of the head and body is 23 cms., while the length of the entire foetus measures 38 cms. There is no external sign of any protrusion of the contents of the spinal canal, and the integument of the occiput passes uninterruptedly down over the back and sacrum. Owing to the shortness of the back, the lower limbs are attached dorsally, while the arms are attached ventrally and only slightly above them, so that the fingers reach down almost to the feet.
On mesial sagittal section, it is at once seen that the deformity is due to malformation of the cranio-vertebral axis, which is much shortened, and forms practically a straight line from the nasal septum to the sacrum. The viscera are consequently pushed downwards and forwards. On the left side a pseudohernia is present, part of the liver and some intestines passing through the diaphragm into the left pleural cavity, where they lie lateral to the left lung. The herniated viscera are not enclosed in a peritoneal hernial sac. Owing to the presence of this hernia, the pericardium and the heart lie wholly on the right side of the medial plane. The various viscera appear normal. The thymus is almost spherical and is placed in the neck just above the sternum. The internal genitals, which are female, are well developed. The suprarenals and the pituitary were both examined microscopically, and were found to be normal.
The cranio-vertebral axis, passing from the anterior end of the nasal septum to the last piece of the sacrum measures 16 cms. and forms practically a straight line, except for a short anterior convexity at about its middle. At its cephalic end can be distinguished the mesethmoid, presphenoid, basisphenoid, basi-occipital, and the cartilaginous anterior arch of the first cervical vertebra. More caudally, in the region of the anterior convexity, there is a mass, in which there are a number of irregular malformed centres of ossification. Here the different vertebrae are indistinguishable. Following this irregular mass, may be seen a number of well formed vertebree, and the 11th thoracic to the 5th sacral may be distinguished. The 5th lumbar vertebra is partly fused with the first sacral. The reduction in length of the vertebral column is thus due to an irregular fusion, or, more correctly, a failure in separation of the cervical and thoracic vertebrae. The vertebral neural arches are -all deficient, none of them uniting posterior to the spinal cord.
The foramen magnum is of large size, measuring 6 cms. antero-posteriorly. It is formed in front by the basi-occipital, and laterally by the ex-occipitals, to which are united the neural arches of the fused vertebrae. Posteriorly the
Fig. 3. Median section showing left side. Fig. 4. Section of Cranio-vertebral Axis,
A, supra-occipital; B, spinal cord; C, thymus; from left side. D, intestine; E, lung; F, liver. A, presphenoid; B, basi-sphenoid; C, basi occipital; D, anterior arch of atlas; E, first lumbar vertebra.
Owing to the section not being exactly mesial, the centre of ossification of the 5th sacral vertebra is not seen.
foramen is completed by the supra-occipitals, which are united behind the spinal cord, opposite the 4th lumbar vertebra. Caudal to this, the remainder of the vertebral canal is covered by the meninges and integument alone. The inter-parietal part of the occipital bone is unossified, but the other membrane bones of the skull are well developed.
The ribs, which are eleven in number on each side, are, in their dorsal parts, fused to one another, and to the vertebrae from which they arise.
The central nervous system was much injured during delivery. There is a mass of nervous tissue, representing the pons and cerebellum, beneath the tentorium cerebelli. Its different parts cannot, however, be distinguished. From this mass a spinal cord runs downwards to the level of the third sacral vertebra.
The cranial nerves are normal, in number and plan. All the spinal nerves are present, and the great plexuses are normal in their constituents and mode of formation, except that the lowest trunk of the brachial plexus is formed by the union of the division of the 8th cervical nerve, the whole of the first thoracic and the greater part of the second thoracic nerves. The remainder of the 2nd thoracic nerve formed the nerve of the first intercostal space, and the succeeding thoracic nerves are each anteposed one space, the 12th thoracic nerve lying below the last, or 11th, rib.
The musculature appeared normal, but the dorsal muscles are very thin.
The more interesting points of the specimen are:
The absence of the neck.
The condition of hydrocephalus.
The deformity of the vertebral column.
The unclosed vertebral neural arches.
The large size and the formation of the foramen magnum. The diaphragmatic hernia.
Following the classification of Ballantyne(1), the above points would lead us to place the monster in the class, iniencephaly. The cardinal characteristics of this type, are a backward bending of the vertebral column with a varying degree of spina bifida, and imperfect formation of the occiput in the region of the foramen magnum. In most cases it is usual to meet with an occipital encephalocele, or a spina bifida with a protrusion of the spinal meninges. Schwalbe (2) would classify the condition under the term Rachischisis. He finds that it is very rare to have all the vertebral neural arches ununited, and that the commoner type is accompanied by a cleavage of the occipital region of the skull. Schwalbe also lays stress on the very interesting feature of the ex-occipitals being fused with the vertebrae. The foetus under examination exhibits this latter condition very well, and also has the rarity of a complete vertebral cleavage with an uncleft occiput. Wheeler(3) describes in detail a most interesting iniencephalic foetus, but her case appears to be of the more common type, and presents a well marked encephalocele.
The condition of iniencephaly is uncommon, nevertheless, Ballantyne had met with seven cases up to the year 1904, The sex is apparently usually female (4).
The etiology is not quite clear. The malformation of the spine is apparently the primary condition, and the closure of the vertebral arches appears to be prevented by the dorsal displacement of the occiput. The absence of the neck is directly due to the shortening of the spinal column, and the diaphragmatic hernia probably results from the Same cause. The malformation of the spine may be due, either to the pressure of the amniotic fluid, or where that is deficient, to the pressure of the uterus itself. More probably it is due to a malformation of the foetus, and not the result of external pressure.
Quite recently Stockard (5), by experimental methods, has shown that most monsters are caused by arrests in development. If we assume that iniencephaly is also due to an arrest, we must look for an embryonic stage in which there is a dorsal concavity of the vertebral axis. Such a stage is represented by His’ embryo 3-2 mm., aged about 3 weeks. Inasmuch as embryos with this dorsal thoracic concavity are themselves regarded as abnormal, we can readily understand that, if iniencephaly is the result of an arrest in this stage, it must of necessity occur but rarely.
(1) Battantyne, J. W. Antenatal Pathology and Hygiene.
(2) Scuowause. Die Morphologie der Missbildungen des Menschen und der Tiere (rn. Teil, 1. Lieferung, 1909).
(3) WHEELER, THEODORA. “Study of a human spina bifida monster with Encephaloceles and other abnormalities.” Contributions to Embryology, No. 22. Public. Carnegie Instit. Wash. 227, pp. 87-110.
(4) Lewis, H. F. Amer. Journ. Obstet. xxxv, 11, 1897.
(5) Stockard CR. Developmental rate and structural expression: An experimental study of twins, 'double monsters' and single deformities, and the interaction among embryonic organs during their origin and development. (1921) Amer. J Anat. 28(2): 115-278.
Cite this page: Hill, M.A. (2020, October 29) Embryology Paper - A human foetus exhibiting iniencephaly and other abnormalities (1922). Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_A_human_foetus_exhibiting_iniencephaly_and_other_abnormalities_(1922)
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