Thus far, the symptoms which occur either in a majority or in a large percentage of cases have been enumerated. The typical course of disseminated sclerosis may be stated as consisting in their gradual development and intensification, covering a period of from four to twenty or more years. There are a number of cases in which so many of the symptoms regarded as typical are either absent or where some given symptom-group preponderates over the others to such an extent that they require special mention.
It is not difficult to understand that disseminated sclerosis may ape other forms of spinal disease. Its symptoms depend on the location of the sclerotic foci. If these are situated chiefly in the crossed-pyramid tract, spastic phenomena will predominate, and the case may resemble a spastic paralysis.126 If they be distributed in both the posterior and lateral columns, the symptoms will resemble those of a combined form of sclerosis in which the tabic and spastic signs are associated, as far as they do not, in the nature of the case, neutralize each other. This was well shown in a case of De Fleury's. Not infrequently an unusually large focus involves the entire transverse section of the cord, and the case becomes complicated by the symptoms of a transverse myelitis. In such a case, described by Rovigli,127 a large transverse focus in the cord had led to ascending secondary degeneration in the column of Goll and descending degeneration of the crossed pyramid tract. In a large series, instances of which are related by Kilian,128 Siemens,129 Schultze,130 Zacher,131 and Greiff,132 the disseminated foci were complicated by a diffuse lesion distributed like that of a diffuse or fascicular myelitis; and there seems to exist every connecting-link between ordinary chronic myelitis, strictly so called, and disseminated sclerosis.
126 Gnauck, Neurologisches Centralblatt, 1884, p. 315.
127 Rivista sperimentale di Freniatria e di Medicina leqale, x. p. 227.
128 Archiv für Psychiatrie, vii. p. 28. He designates this form sclerosis continua multiplex.
129 Ibid., x. p. 135.
130 Ibid., xi. p. 216.
131 Ibid., xiii. p. 168.
132 Ibid., xiv. p. 287.
Not only does disseminated sclerosis occasionally imitate or approximate the regular (fascicular) affections of the cord, as well as diffuse cerebro-spinal affections, but it may appear under the mask of a nuclear oblongata paralysis.133 And cases are on record where, in addition to the disseminated sclerosis, there occurred sclerotic atrophy of an entire hemisphere or of its capsular tracts, thus leading to a hemiplegic resemblance of the motor paralysis. In my experience the cases presenting the type of a nuclear oblongata paralysis run a more rapidly fatal course than others. The shortest history in my series, one of four years, was of such a case. A number of instances are on record by careful observers—and are probably much more numerous than is commonly suspected—where no decisive evidence of spinal or cerebral disease could be detected during life, and yet disseminated foci of sclerosis existed in the nerve-centres. In such cases the symptoms may be in the direction of simple nervous prostration, more commonly of spinal irritation. I have now under observation a case which for years had been regarded as one of spinal irritation, and which made that impression on me until I discovered the existence of optic-nerve atrophy, which was the only indication that the symptoms depended on gross structural disease.134