133 It is customary to speak of symptoms referable to the oblongata as bulbar. The designation bulbus rachidicus is now obsolete, and just as we speak of a capsular hemiplegia, a pons paralysis, or a spinal hemiplegia, so we should say an oblongata paralysis, discriminating between the nuclear, the neural, and the tract affections by means of a prefix.
134 At present the symptoms of disseminated sclerosis are unmistakable. Cases are mentioned by Strümpell and others in which they remained indecisive throughout.
Among the anomalous forms of disseminated sclerosis there is one which is characterized by the preponderance of paraplegia and contractures in a combination which is usually found in spinal diseases of a different type. The coexistence of dementia, however, usually enables the observer to determine that the lesion is both cerebral and spinal, although those signs which might enable him to decide the disseminated focal character may be absent.
MORBID ANATOMY.—In advanced cases of disseminated sclerosis the lesion is visible to the naked eye on the surface of the brain and spinal cord. Grayish maculas, sometimes elevated, more rarely a little sunken, and occasionally showing a buff or reddish tinge, are seen on the surface of the spinal cord, the oblongata, pons, and crura. On making sections across the region of the spots, it is found that the color-change is not superficial, but extends inward, involving large parts of the transverse area of the cord or the cerebral axis; and patches lying more deeply in their substance are revealed whose existence could not have been suspected from a mere surface inspection. Exceptionally, patches are found involving the entire transverse section of the spinal cord in a length of a half to two inches. And, similarly, in the brain nearly the entire area of the pons or one of the crura or an entire division of the internal capsule may be occupied by a sclerotic focus. Otherwise, they may vary from almost microscopic dimensions to the size of a chestnut or even larger. Bourneville135 has described cases in which the nerve-centres appeared normal to the naked eye, while the microscope revealed the existence of sclerotic foci. It is, however, unlikely that the fresh brain- and cord-tissue, when the site of disseminated sclerosis, will appear perfectly healthy to the naked eye under fairly good illumination. Much less intense lesions than those of disseminated sclerosis reveal their presence by changes in color and consistency.
135 Mouvement medicale, 1869, No. 27.
On examining the diseased spots more narrowly, they are found to be slightly diaphanous. Usually, they are rounded or elliptical, but they are often drawn out, as it were, in the most irregular shapes, and not infrequently appear to be the result of a confluence of originally remote and separate foci. In the cord they are sometimes wedge-shaped, extending inward from the periphery. To the touch they appear firm—sometimes not much more so than the normal tissue, contrasting with it as hard-boiled white of egg would contrast with soft-boiled; in advanced cases they become of almost leathery consistency, and there are instances recorded where they actually creaked under the knife. A clear fluid usually runs from their cut surface, and the latter does not jut up on section like normal nerve-tissue.
The distribution of the diseased areas follows no known law. They may be numerous and of large size in one segment of the nervous axis, and small, few in numbers, or even absent, in others. In some altitudes of the cord the lateral, in others the posterior, in still others the anterior, columns are chiefly involved. The cerebrum usually contains a larger number of foci irregularly scattered in the centrum ovale of Vieussens, the internal capsule and its surrounding ganglia, as well as in the corpus callosum. Throughout the nervous axis it seems that the lesion chiefly affects the white substances, and even the roots of the peripheral nerves, both cranial and spinal, are occasionally found to contain small foci, gray, firm in consistency, and as distinctly outlined as those of the central organs.
The morbid process consists in an atrophy and gradual disappearance of the myelin, which is preceded, if not caused, by an increase of the enveloping interstitial substance. This change is of the same character as that found in chronic myelitis. The septa and trabeculæ of connective tissue become thicker, formless connective substance and fibrillar tissue, which seems to arise in, if not in part from, it, constituting the new formation. The neuroglia-nuclei are increased, enlarged, and develop into spider-shaped cells, whose long processes contribute (according to some authors exclusively) to the newly-formed fibrillar network.
While the myelin undergoes wasting, the axis-cylinders remain intact for a long period, and even in intensely sclerosed regions they may be found in nearly their normal number, but naked and in direct contact with the pathological fibrillæ. Some of them become hypertrophied, increasing to twice, thrice, and, according to Leyden, even more, of their normal diameter. This change seems to inaugurate the last phase of the process: the axis-cylinders, becoming sclerosed and brittle, ultimately disappear, and no trace, or at best but doubtful traces, of the normal nerve-tissue are left behind. The blood-vessels, following the rule of the sclerotic process, take part in it. Their walls become thickened, richly nucleated, and the lumen becomes narrowed in consequence. In the smaller vessels complete obliteration of the lumen is sometimes observed.
The gray substance is not involved as frequently as the white, but it opposes no barrier to the extension of the morbid process when once established in its neighborhood. The nerve-cells show the same resistance which the axis-cylinder does; that is, they retain their outline and fibre-connections a long time in the midst of the diseased area. But eventually they become discolored, undergo hyaline or granular disintegration, their processes shrink, and finally they disappear.