These three forms are only of interest to neurologists and alienists.
Insular sclerosis, or sclerose en plaques, is defined by Osler as a chronic affection. ' of the brain and cord in which the nerve elements are more or less replaced by con nective tissue. It may occur in the brain or cord alone, but is more commonly found in both.
Symptoms.—According to the varying location of the foci, the symptoms may be, to a certain degree, variable, and the majority of the classical symptoms may be absent. The development of the dis ease is slow and the course is chronic. Feebleness of the limbs, with irregular pains and stiffness, is the earliest symp tom. The resemblance is sometimes very close to spastic paraplegia with great in crease in the reflexes.
Later three important symptoms ap pear: volitional tremor, or so-called in tention tremor; scanning speech; and nystagmus.
Volitional tremor is a trembling that comes on when muscular action is at tempted. The tremor may be noticed in the extremities or head. When the pa tient is quiet the tremor disappears.
By scanning speech is meant that in reading or speaking each word is pro nounced slowly or separately, or each syllable may be accentuated. This is a common feature. Nystagmus, a rapid os cillatory movement of the eyeballs, gen erally horizontal, is an important symp tom. Optic atrophy, though not so fre quent as in tabes, is sometimes present. The sphincters are usually unaffected until late in the disease. In most cases sensation remains intact. Mental de bility is not infrequently present. Ver tigo is not uncommon; there may be sudden attacks of coma, as in general paresis. Remissions occur, sometimes at intervals of many years, in which all the symptoms may greatly improve. In all cases in which paresis of one or of several extremities disappears only to reappear much later on, insular sclerosis must be suspected (Buzzard).
Diagnosis.—The symptom-complex of volitional tremor, scanning speech, nys tagmus, and more or less spastic weak ness of the legs usually renders diagnosis easy in typical cases. In its early stage it resembles very closely hysteria; the nystagmus, the vesical disturbances, and the volitional tremor will be useful in differentiating them. The tremor in hysteria is not volitional. Paralysis agitans and certain cases of general pare sis simulate this disease so closely that, near the end of the disease, differentia tion may be impossible.
Westphal's en plaques is still more difficult to differentiate.
Diffuse sclerosis of the brain is not a congenital affection, but it attacks pre viously-healthy individuals. It is quite distinct from multiple sclerosis. The dif ferential diagnosis between diffuse cere bral sclerosis and cerebral tumors is very difficult on account of the extreme rarity of the affection. 0. Heubner (Charite Annalen, xxii, p. 293. '97).
Disturbance of vision is the initial symptom of multiple sclerosis, and is by no means rare. Frequently it is difficult
to elicit the symptoms, however, for the patients have forgotten it. It is particu larly important, because in many cases it renders possible the differential diag nosis between multiple sclerosis and syphilis of the brain. Frank (Dent. Zeit. f. Nervenk., Dec. 22, '98).
Etiology.—The etiology of this disease is obscure. Scarlet fever and other in fections diseases have been referred to in this connection. Although not frequently occurring in children, it is most common in young adults. Trauma, congenital predisposition, and metallic poisons have been mentioned as etiolog ical factors.
Two eases, due to influenza, in which selerous encephalitis was consecutive to an infectious circumscribed arteritis. H.
llendu (Comptes Rendus Heb. des seances de l'Acad. des Sci., Paris, Dec. 21, '94).
Pathology.—The grayish-red areas are scattered indifferently through the white and gray matters (E. W. Taylor). The selerosed patches are most abundant in the neighborhood of the ventricles, and in the pans, cerebellum, basal ganglia, and the medulla; histologically in the sclerosed patches there is marked pro liferation of the neuroglia, the fibres of which are denser and firmer; the gradual growth destroys the medulla of the nerves, but the axis-cylinders persist in a remarkable way (Osier). Redlich, of Vienna, finds several processes: either there is a pronounced thickening of the neurogliar tissue, containing the remains of the nerve-fibres, above all, of bare axis-cylinders, or it will be found that, with a relatively slight alteration in the neurogliar tissues, the nerve-fibres are missing, in which case a fine, thin net work has replaced them. Redlich does not believe it proved that the process originates as an inflammatory one in the vessels, or that the neurogliar prolifera tion is the primary factor, but rather in clines with O. Huber to the opinion that the process is one of degeneration af fecting particularly the nerve-fibres. He explains the presence of the volitional tremor as a functional weakness of the nerve-apparatus, as there is no anatom ical localization for this symptom. He classes nystagmus with the volitional tremor as having no anatomical localiza tion. Scanning speech is most likely re ferred to the sclerotic areas in the pops and in the medulla oblongata (its favor ite location); speech must naturally be first to suffer from areas of sclerosis in the bulb, since it requires the finest in nervation, being the most complicated of the physiological processes.
Prognosis.—The prognosis is unfavor able. The patient becomes bedridden unless he dies in the meanwhile of some acute disease.
Treatment.—No known treatment has any influence on the progress of sclero sis of the brain, but a prolonged course of nitrate of silver may be tried, and ar senic is recommended (Osier).