Page:A manual and atlas of medical ophthalmoscopy.djvu/146

130 The neuritis of tumour is in most cases double, sometimes equally advanced in the two eyes, often more intense and subsiding earlier in one than in the other. Rarely the affection of the disc is unilateral (as in Case 17), and this, although the tumour may be in the brain, where growths commonly cause double neuritis. In two cases of this character recorded by Dr. Hughlings Jackson, the neuritis was on the opposite side to the tumour.

Symptoms.—The symptoms of the neuritis which accompanies cerebral tumour have been already fully described (p. 54). It must be remembered that all symptoms may be absent, the acuity of vision, the fields of vision, and colour vision may all be unaffected, as in many of the cases figured in the plates and referred to in the description of the symptoms of neuritis. It must also be remembered that affections of sight of various kinds may co-exist with neuritis, and be due, not to the intra-ocular, but to the intra-cranial disease.

Course and Duration of the neuritis in cerebral tumour.—It is important to note that the neuritis often coincides at its onset with an obvious increase in the other symptoms of the cerebral tumour. This has been pointed out, long ago, by Dr. Hughlings Jackson. Instances of it are frequent, but at the same time exceptions are not rare. It is probably true, however, that the occurrence of optic neuritis indicates progress in the morbid growth and its consequences.

With regard to the course of the neuritis, it is necessary to distinguish two classes of cases. One of these is where the progress of the tumour, either spontaneously, or under the influence of treatment, becomes lessened or arrested after the onset of the neuritis; the other, where the progress of the tumour to which the neuritis is due is uninterrupted.

In the first event, the neuritis commonly subsides. It may pass away completely, even although it has reached the stage of considerable swelling and obscuration of disc and vessels, with distended veins and narrowed arteries, and sight may throughout be unimpaired. This occurred, for instance, in the cases shown in Pl. IV. 1, 2, 3, 4, V. 3, 4. Or, less