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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    has recently come to light in this v;ork, which demands a reorientation of attitude towards it (23). In the course of a closer investigation of the labyrinth and 3th nerve in young animals brought up on the vitamin A deficient diets described above, serial sections of the decalcified petrous portion of the temporal bone were cut and it was found that, associated with the disappearance of the cochlear and vestibular divisions of the nerve, there was much new bone formation, which was not present in the control animals on the same diet but receiving vitamin A or carotene In addition. This new bone was found in two positions. In each case of periosteal origin:-(a) in and near the modiolus itselfj this bone presses on the nerves as they leave the cochlea and vestibule respectively; (b) around the Internal auditory meatus, adjacent to the brain. ' This has the effect of placing the cochlea deeper into the capsule and of increasing the distance from the spiral and Scarpa1s ganglia to the brain, a change which stretches and twists the nerve. Occasionally new bone can be seen in a third place, namely In the scsla tympani at the basal whorl of the helix. Closer study of this condition leaves no doubt that the bone overgrowth in these places results finally in the destruction of the fibres of the 8th nerve. After the discovery of these facts, it was necessary to see whether all the nerve degenerative change, s previously described could be attributed to bone overgrowth and the pressure and stretching effect of such growth on the nerve fibres or pressure on nerve cells resulting therefrom. While It IS impossible as yet to say that this is the case, the following statement summarises In brief other pathological conditions which have come to light. It has been found. for Instance, that with vitamin A deficiency there Is an overgrowth of the petrous ridge and to some extent of the bone supporting the Gasserian ganglion. This results in compression both of the ganglion and of the fifth nerve centrally to the ganglion. The ganglion becomes elongated and the central root of the nerve bent. In an advanced case the enlargement of a small portion of hone partially plugged the foramen of the 5th nerve. Transverse sections of the optic nerve and the bone surrounding it also showed partial closure of the foramen and compression of the nerve by bone overgrowth. It Is clear, therefore, that, so far as the brain is concerned, degenerative changes in the second, fifth and eighth nerves are all assoc¬ iated with hone overgrowth at the base of the skull, and it may well he that this hone overgrowth is responsible for the degenerative changes previously described in these nerves.