A special form of the condition under discussion is called spina bifida occult°. In this anomaly, which is usually situated in the lumbar region, there is likewise a cleft in the vertebral column and the spinal marrow is deformed, but there is no accumulation of fluid and there fore no protruding sac. Whether spina bifida occulta is the expression of an intra-uterine process of repair, or, as Hildebrandt no doubt cor rectly assumes, a special malformation genetically representing the terminal member of the entire series of spinal hernia, is still an open question. The anomaly is characterized by failure of the vertebral canal to close, the occurrence in the spinal canal of fibromuscular tu mors due to developmental processes, and by the fact that the spinal marrow is continuous with the external skin (Katzenstein). Externally the malformation manifests itself by a spherical prominence usually situated in the sacral region; sometimes by a depression covered with normal or cicatricial skin and hair such as is not normally present in that situation. Sometimes the cleft in the bone or the above-mentioned muscular tumor can be palpated through the superficial tumor.
The signs of spina bifida occulta are quite remarkable. Congenital palsies are not common and are confined to clubfoot, pes equinus or sensory disturbances. On the other hand, certain more pronounced symptoms, such as incontinence of urine, perforating ulcer, neuralgias and palsies, manifest themselves in the later years of childhood and at the times of puberty. Hence the great majority of reported cases refer to individuals between childhood and adolescence, and the dis covery of the condition when the patient is examined usually causes great surprise. I myself know two half-grown boys whose general health is good and who suffer from constantly increasing incontinence of urine, attributable to a spina bifida occulta. Katzenstein has ofTered a very plausible explanation for the late occurrence of the disturb ance; during the normal upward growth of the spinal cord within the vertebral canal, the connecting band between the spinal cord and the skin is subjected to traction, causing distortion of the spinal cord and the gradual development of functional disturbances. Indeed, the removal of such connecting bands has in some cases been followed by disappearance of the disturbances caused by the spina bifida occulta. The operation is therefore distinctly to be recommended as, without such intervention, the symptoms may be expected to increase in severity.
9. Partial congenital changes of the central nervous system.—In addi
tion to the congenital disturbances which manifest themselves partly as conspicuous inalforrnations and partly as distinctly recognizable diseases, we find in the nervous system a number of changes affecting a limited area, and which are, according to their seat and extent, of interest to the clinician, or merely of pathologic significance.
(a) Brain.—In the brain we have absence of the corpus callosum (Zingerle, Anton, Hochhaus), changes in size of the convolutions (macro gyria and microgyria), and aplasia of the cerebellum. The latter will be referred to again in connection with hereditary ataxia.
(b) Of much greater importance are the congenital aplasias in the nuclear region of the medulla oblongata (infantile nuclear atrophy). There are certain congenital conditions characterized by complete or partial immobility of the eyes (oplithalmoplegia) absence of facial expression, atrophy of the tongue and interference with its movements, a constant flow of saliva from the mouth, and absence of the lachrymal secretion. These disturbances may be unilateral or bilateral, and the above symptoms may be present only in part. They correspond to paralysis of the ocular muscles, of the facial hypoglossus, etc. Most frequently this congenital motor impairment is limited to the eye and shows itself either in complete immobility of the eye or absence of certain movements, especially in unilateral or bilateral ptosis.
The pathologic foundation in a case of Heubner's was found to be absence of the motor nuclei in the medulla oblongata, namely those of the abducens, facial and hypoglossus. The findings in this case accord ingly fully justify the theory of partial lack of development of the central nervous system—infantile nuclear atrophy (Altibius). It seems prob able, however, from certain exhaustive investigations by Nunn that the above pathology does not apply to all cases of congenital motor impairment of the eyes and bulbar nerves, and that congenital changes may occur anywhere in the path between the nerve centres controlling the ocular movements and the ocular muscles, and produce motor dis turbances. Again, these congenital palsies must be sharply separated from those which develop during childhood. It is thought advisable therefore, to divide all motor defects of the eyes, with or without in volvement of the bulbar nerves, into several groups and to distinguish between congenital and acquired changes, between disturbances of nervous, and those of muscular origin. We shall return to the discus sion of these conditions after considering muscular palsies.