SCLEROSIS OF THE BRAIN.—Scle rosis of the brain is a condition which results from a chronic inflammation of the cerebral tissue, which inflammation may arise primarily in the connective tissue or secondarily by extension or contiguity, and is analogous in many re spects to that inflammatory action which is associated with cirrhosis of the liver. The connective tissue of the brain is of two distinct varieties, one of which, the neuroglia, is derived from the ectoderm and forms the net-work or mesh which holds together the central nerve-cells and ganglia of the brain-substance proper; the other, derived from the mesoderm, forms the basic substance of the meninges and the sheaths and sup porting structure of the blood-vessels, being identical with the ordinary fibrous or connective tissue found elsewhere throughout the body. Both varieties are concerned in this process of sclerosis (in duration or hardening).
Osier suggests a convenient division of the cerebro-spinal scleroses, from an eti ological stand-point, into degenerative, inflammatory, and developmental forms.
the head of degenerative forms he includes: (a) the common degenera tion which follows when nerve-fibres are cut off from their trophic centres (the severance of portions of neurons from the main portions containing the nuclei); (b) toxic forms following poisoning by lead, ergot, syphilis, etc.; (c) the scle roses associated with senile changes in the smaller arteries and capillaries in the convolutions. Some forms of insular sclerosis (sclerose en plaques) are prob ably due to primary alterations in the blood-vessels; it is not proved, however, whether these cases are caused by im paired nutrition resulting from lesions of the capillaries and smaller arteries, or whether the lesion is a primary degenera tion of the nerve-cells and fibres to which the sclerosis is secondary.
The inflammatory scleroses include secondary forms which develop in con sequence of irritative inflammation about tumors, foreign bodies, h(em orrhages, and abscesses. These are chiefly vascular (mesodermic) scleroses, arising from the connective tissue about the blood-vessels. A similar change may
possibly follow the primary, acute en cephalitis, which Striimpell holds is the initial lesion in the cortical sclerosis found in infantile hemiplegia.
Osier's third group. the developmental scleroses, are believed to be purely nen rogliar (ectodermic) in character, and embrace the new growth about the cen tral canal in syringomyelia; the sclerosis of the dorsal columns in Friedreich's ataxia; and, perhaps, the congenital diffuse cortical sclerosis without thicken ing of the meninges. If both the ecto dermic and mesodermic connective tis sues be involved, the resulting sclerosis will be of a mixed character.
When considered by their appearance, distribution, and anatomical formation, cerebral scleroses are known as miliary, diffuse, tuberous, and insular scleroses.
Miliary sclerosis is a name for sev eral different conditions. In one variety there are small nodular projections, vary ing from one-half to five or more milli metres in diameter, upon the surface' of the convolutions; single nodules are not uncommon; they may be found some times in great numbers. Gowers reports a case in which grayish-red spots were found located at the junction of the white and gray matters; the neuroglia was in an hypertrophic condition.
Diffuse sclerosis may involve a single lobe (sclerose lobaire) or an entire hem isphere. This condition occurs most frequently in idiots and imbeciles. In extensive cortical sclerosis of one hemi sphere the ventricle is usually dilated (Osier). The region affected and its ex tent will determine the symptoms, al though there may be no symptoms and but little noticeable impairment of the mental powers. There is, in the majority of cases, hemiplegia or diplegia, with idiocy or imbecility.
Tuberous sclerosis, also known as hypertrophic sclerosis, is applied to a condition in which there are opaque, white, firm, projecting areas located upon the surface of the convolutions, which may not affect the symmetry of the convolution, but give it an increased size and density and a change in color.