Like tabes dorsalis, the progress of disseminated sclerosis is often marked by episodes. Some of these differ in no way from the visceral crises of posterior-column sclerosis; every form of these symptoms found with that affection may occur in the present one, while episodes involving the cerebral functions are much more common. The latter manifest themselves as apoplectiform or epileptiform seizures. They are preceded by headache and vertigo, or, if these be continuously present, by an aggravation of them; then unconsciousness develops, either accompanied by convulsions or not, and the face is flushed, the pulse full and frequent, and the temperature raised. Consciousness returns in a few hours or a day, the attack rarely lasting more than two days, and it is found that the patient is hemiplegic. But, unlike the hemiplegia found after vascular rupture, embolism, or structural cortical disease, it is rapidly recovered from.
In a case of Gnauck's an attack of scotoma scintillans, associated with a noise of thunder in the right ear and pricking pains on the right side of the face, preceded anæsthesia and the formation of a small defect of the visual field.
There is a close resemblance between these apoplectiform and epileptiform seizures and those of paretic dementia, not alone in clinical character, but also in the surprisingly complete and rapid recovery from the more serious symptoms. But just as in paretic dementia, especially in its advanced stage, each seizure leaves the patient somewhat more impaired in mind and body than he was before, so it is in disseminated sclerosis; each attack marks a step forward in the invasion of the morbid state.
Eye-trouble is much less frequently a premonitory sign of disseminated sclerosis than of tabes. A few such cases are on record. Magnan observed the development of the characteristic symptoms of disseminated sclerosis fourteen years after an amaurosis which followed typhoid; and Gnauck reports another in which first a right ptosis, and then a right amblyopia, preceded the ordinary symptoms. In exceptional cases this premonitory eye-trouble may, like that of tabes, rapidly lead to extreme amblyopia or even amaurosis. The visual disturbances are remarkable for their rapid changes. They appear within a short period, attain their maximum rapidly, and may occasionally retrograde as quickly. They develop under two forms—the central and the peripheral scotoma, or, rather, limitation of the visual or color field. The former, like the amblyopia of alcoholic and nicotine intoxication, consists in an inability to differentiate between red and green in the centre of the visual field. It never, in my experience, proceeds as far as the toxic amblyopias; that is, to the complete extinction of vision.123 The peripheral limitation of vision may be for both quantitative and qualitative light-perception, but it is not, as a rule,124 concentric as in tabes, but sector-like.
123 Gnauck says that the central color-blindness may become total, and the red-green blindness extend to the periphery.
124 Concentric limitation of ten to thirty degrees has been noted for color-perception.
The atrophy of the optic nerve in disseminated sclerosis is typically partial, in the majority of cases manifesting itself as a sharply-marked discoloration of the temporal half of the papilla. In others the nasal half of the papilla also becomes discolored, but so much less intensely that the difference between the earlier involved and later involved portions is quite easy. It is doubtful whether the subjective visual disturbance is always an indication of the extent to which the optic nerve is involved. There are good reasons for believing those amblyopias and limitations of the field of vision which show marked remissions and exacerbations to be due to some dynamic central condition involving the visual centres and tracts. Thus it has been observed that almost total amaurosis occurred after an apoplectiform attack, to disappear later on. Occasionally the amblyopia is bilateral and the optic-nerve lesion unilateral. The frequency of this affection is stated by Gnauck125 as follows: In one half the cases there is diminished vision, and in half this half optic-nerve atrophy with limitation of the visual field. It is only in exceptional cases that an optic neuritis can be determined to have preceded the atrophy.
125 Of 50 cases, 22 had no visual trouble, 8 showed simple diminution of perception, 5 added limitation, and 15 changes of the optic disc, a case of total atrophy and amaurosis being included in the latter.
The pupils are perfectly normal in some cases; in others myosis of the spinal type is observed; and this I found to be nearly constant in all advanced cases. Irregularity in outline and inequality exist in a small proportion, and reflex iridoplegia is found in about 10 per cent. of the cases.