McAlpine and coworkers (1972) analyzed the mode of onset of MS in 219 patients and found that in 20 percent the neurologic symptoms were fully developed in a matter of minutes, and, in a similar number, in a matter of hours. In approximately 30 percent the symptoms evolved more slowly, over a period of a day or several days, and in another 20 percent more slowly still, over several weeks to months. In the remaining 10 percent the symptoms had an insidious onset and slow, steady, or intermittent progression over months and years. The typical relapsing–remitting pattern of disease is more likely to appear in patients who are younger than 40 years of age. Certain paroxysmal symptoms and signs may occur in the established phase of the disease and discussed in the following text. The inflammatory process of MS affects no organ system other than the CNS.
Optic Neuritis (See Chap. 12)
In approximately 25 percent of all MS patients (and possibly in a larger proportion of children), the initial manifestation is an episode of optic neuritis. It will be recalled that the optic nerve is in fact a tract of the brain, and involvement of the optic nerves is therefore consistent with the rule that lesions of MS are confined to the CNS. Characteristically, over a period of several days, there is partial or total loss of vision in one eye. Many patients, for a day or two before the visual loss, experience pain within the orbit, worsened by eye movement or palpation of the globe. Rarely, the visual loss is steadily progressive for several weeks, mimicking a compressive lesion or intrinsic tumor of the optic nerve (Ormerod and McDonald). Usually a scotoma involving the macular area and blind spot (cecocentral) can be demonstrated, but a wide variety of other field defects may occur, rarely even hemianopic involvement (sometimes homonymous). In some patients, both optic nerves are involved, either simultaneously or, more commonly, within a few days or weeks of one another, and at least 1 in 8 patients will have repeated attacks.
Examinations may disclose evidence of swelling or edema of the optic nerve head (papillitis) in about one-tenth to one-third of patients. More often, the optic nerve head appears normal in the acute phase of optic neuritis; this represents retrobulbar neuritis. The presence of visible optic disc swelling depends on the proximity of the demyelinating lesion to the nerve head. As emphasized in Chap. 12, papillitis can be distinguished from the papilledema of increased intracranial pressure by the severe and acute visual loss that accompanies only the former. Subtle manifestations of optic nerve affection, such as an afferent pupillary defect, atrophy of retinal nerve fibers, or sheathing of retinal veins and abnormalities of the visual evoked response (Chap. 2), may be sought in patients who have no visual complaints but are suspected of having MS. Visual evoked potentials and optical coherence tomography (OCT) may be useful in detecting changes consistent with prior optic neuritis, as discussed in a later section and in Chap. 2.
As noted in Chap. 12, about half of patients with optic neuritis recover completely, and most of the remaining ones improve significantly, even those who present initially with profound visual loss (Slamovitis et al). Pain around the eye is short-lived and persistent pain should prompt an evaluation for local disease. In a cohort of 397 patients enrolled in the Optic Neuritis Treatment Trial and examined 5 years after the initial attack of optic neuritis, visual acuity had returned to 20/25 or better in 87 percent of patients and to 20/40 or better in 94 percent—even if there had been a recurrence of optic neuritis during the 5-year period. Moreover, the mode of treatment did not appear to influence the final visual outcome. Dyschromatopsia and impaired contrast sensitivity frequently persist, as does the Pulfrich effect, wherein an object such as a pendulum that is swinging perpendicular to the patient’s line of sight appears to move in a three-dimensional, circular path.