Neurological aspects of the avitaminoses : with special reference to the peripheral nervous system / by Sir Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1939?]
Catalogue details

Licence: In copyright

Credit: Neurological aspects of the avitaminoses : with special reference to the peripheral nervous system / by Sir Edward Mellanby. Source: Wellcome Collection.

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    The whole base of the skull is affected, by this bone overgrowth and the enlargement of the posterior and anterior clinoid processes has a compressing effect on the hypophysis. It may be added that not only is the base of the skull affected in this way but there is also some hypertrophy of the frontal, parietal and occipital bones. In fact, the overgrowth round the foramen magnum may be so great as almost to obliterate the cisterna magna* It Is interesting to note In this connection that in some of the animals on these diets which show nerve defects, the pressure of the cerebro-spinal fluid is greatly Increased and It may well be‘that it is the bone overgrowth round the foramen magnum which accounts for this abnormality* With the Increased pressure the choroid plexus may be bunched up and Its structure altered greatly* Morp recently the investigation has been extended to the changes in the .vertebral column and here again it is now possible to say that bone overgrowth takes place in that -part of the vertebra where the nerves respectively enter and leave the spinal column, and there can be little doubt that pressure at these points may well cause the destructive changes in the nerves referred to* F-. * If the nerve degenerative changes In peripheral nerves were due to bone pressure, as seems probable, the explanation > of the curious differences between the afferent and efferent • nerve roots of the spinal cord would also be satisfactory* Examined inside the spinal canal, the posterior roots showed much degeneration in these animals, and the anterior roots were free from degeneration'. Since the actual overgrowth of bone affected these nerves as they left the spinal canal, the pressure on the nerves would destroy the afferent nerves centrally to the posterior ganglion but would leave the anterior root fibres central to the point of injury intact. On the peripheral side of the pressure, no doubt both afferent and efferent nerves were degenerated. The same explanation can probably be given of the normal appearance of the 7th nerve Inside the skull. Pressure on this nerve also was applied by bone overgrowth at the base of the skull and In one case at least peripherally to this pressure the 7th nerve was degenerated while centrally it escaped. It may be. added that the femur, radius and.ribs of these animals are also affected and it seems probable that the whole osseous system'is modified by this deficiency. As was originally pointed out, the new bone growth Is very cancellous and contains many large marrow spaces, in contrast to the normal and more compact bone of animals receiving adequate vitamin A or carotene.