Page:A manual and atlas of medical ophthalmoscopy.djvu/145

Rh pass away, in many cases leaving atrophy of the discs, while the symptoms of the tumour continue or increase for months or years. It is not only that a tumour takes a certain time to cause optic neuritis, but it often exists for a considerable time before the mechanism for the production of neuritis, whatever that may be, is set in operation. A tumour may exist and cause symptoms for years before optic neuritis is produced. A striking instance of this is afforded by Case 15; the microscopical appearance of part of the papilla is shown in PI. XIV. 7. The case was under the care of Dr. Hughlings Jackson, who had examined the eyes repeatedly during nine months and always found them normal. Then neuritis came on, but subsided, and in six weeks the discs were again normal, and continued so till death. Dr. Jackson has recorded a still more significant case in which a man had had symptoms of cerebral tumour for nine years: during the last three years his discs had been repeatedly examined and found normal. Six weeks before death neuritis was discovered.

In many cases in which neuritis occurs long after the symptoms of tumour have existed, its occurrence precedes death by no long interval.

The appearance of the discs in intra-cranial tumour is that of neuritis in its most typical forms, as described in a preceding page (p. 42). The stages indicated may be seen, and the neuritis may stop at one or another of those stages, constituting what may be termed varieties of neuritis. As already stated, until our knowledge of the relation of the appearances to their causes is much more extensive, and founded on more minute and full observation of the conditions of origin, macroscopic and microscopic, a division of neuritis into varieties according to its degree is much more useful than a separation of forms according to hypothetical modes of origin. Those varieties or stages have been already enumerated (p. 75). Each of the earlier stages may or may not be accompanied by obvious over-distension of veins, and each may be accompanied by extravasations.