The treatment of subacute combined degeneration / by Edward Mellanby.
- Mellanby, Edward, Sir, 1884-1955
- Date:
- [1933?]
Licence: In copyright
Credit: The treatment of subacute combined degeneration / by Edward Mellanby. Source: Wellcome Collection.
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![It can be said at once that, if there is any such relationship between the animal experiments just described and subacute combined degeneration of the cord in man, it cannot be as direct, as appears to be the case between these experimental results and such nutritional diseases as convulsive ergotism, pellagra and lathyrism. In all the latter there is strong evidence that a vitamin-A deficiency, associated with excessive intake of some foods containing neurotoxic elements, accounts in large part for the nerve lesions. This suggestion does not, of course, preclude the possibility of other factors being also involved. In subacute combined degeneration, however, the complete absence of vitamin A from the food or from the body is unlikely, and since the experimental lesions only develop in animals when there is little or no vitamin A stored in the body, this single explanation cannot alone account for the clinical condition. Because a substance such as vitamin A is present in the food, it does not mean that it is effective. It may not be stored in the body, or it may not be transferable to some seat of action, or its effectiveness may depend on the presence of a correct amount of some other chemical agent. It can be stated definitely, however, that not only does subacute combined degeneration develop when there is vitamin A in the diet, but also that this substance is stored in the liver in this disease, so that, if it is ineffective, it is for some other reason. It is, however, only with much hesitation that I advance an argument of this type, because we have in recent times become so accustomed to see the specific effects of deficiency and excess of certain substances of physiological importance that it is difficult to imagine conditions where they are ineffective when present or, when absent or deficient, that processes which they control can be normal. Such occasions do arise, however, as, for instance, in diabetes mellitus, when the pancreas contains insulin which is relatively ineffective. We know also from the work of Houssay that whether insulin is active or not depends on the condition of the pituitary body, and the loss of the pituitary gland greatly increases the susceptibility of tbe animal to insulin. Thus removal of the pancreas does not produce diabetes in an animal deprived of its pituitary body. Another instance of a similar nature is seen in the case of thyroxine, a substance which in minute quantities raises the basal metabolic rate of normal animals. In patients with nephrosis, however, it is difficult to raise their metabolism by this means. Thus there are analogous cases which show that the effectiveness of specific active principles can be modified by other metabolic changes. Now it happens that in subacute combined degeneration, whatever the metabolic basis at fault, there is good evidence which shows that chemical elements quite sufficient in amount in the normal body to carry out their function, are insufficient to work effectively in controlling the nervous tissues. Thus it is generally accepted that the amount of liver or liver extract sufficient to improve the blood condition in pernicious anaemia to one approaching normality, say with a haemoglobin reading of 80%, is insufficient to prevent the onset of subacute combined degeneration or to improve it, if it has already developed. Some claim, however, that, if the haemo¬ globin content of these patients be increased to 100% by giving huge amounts of liver extract, the nerve disorder is prevented, or improved if present. Thus, even if we accept the view that the chemical agent responsible for the blood improvement and the nervous system control is the same, it is obvious that in these associated diseases very much larger quantities of this substance are necessary for the pro¬ tection of the nerve metabolism than for improvement of the blood condition—a quantity out of all proportion larger than that effective in the normal man. Or take the iron treatment as recommended by Sargant [6]. The body is loaded with iron in pernicious anaemia at a time when the blood condition is bad and subacute combined degeneration is developing rapidly. If Sargant’s deduction from his results is correct—that excessive iron therapy in the form of 120 to 150](https://iiif.wellcomecollection.org/image/b30629603_0004.jp2/full/800%2C/0/default.jpg)
