CEREBRAL SOFTENING. - The concept of cerebral softening is fairly precise and defined from an anatomo-pathological point of view, much less so from a pathogenetic and clinical point of view. By cerebral softening is meant an alteration of the cerebral substance that appears in foci of varying size, sometimes single, more often multiple, sometimes so diffuse as to involve the brain in its entirety.
Softening is not an alteration exclusive and peculiar to the cerebral substance, since it can also involve the other organs, and it consists essentially in a focus of necrosis generally followed by a reparative process, by which the destroyed cellular elements are eliminated and replaced with fibrous filling tissue. The site, the size, the singleness or multiplicity, the stage, recent or late, at which it is observed, make the picture of cerebral softening very varied. A recent focus appears to the naked eye as an area of varying size with indistinct borders, of a whitish-yellowish color (white softening or ischemic necrosis) or tending toward brown (red softening or hemorrhagic infarct), of soft consistency or in any case diminished with respect to the surrounding healthy tissue. The central part becomes colliquated, "softens," while at the periphery a fibrous-scarring tissue forms that can surround and isolate the colliquated part from the rest of the parenchyma (formation of a cyst) or eliminate or replace it (sclerosis). Sclerosis represents the outcome of a reactive process of the supporting or "glial" tissue ("glial reaction") toward the softened zone.
Although the mechanism by which it forms is still a matter of discussion, cerebral softening can, for simplicity, be attributed to a disturbance of the blood circulation entailing a diminution of the blood supply to the cerebral substance: the affected area suffers from the lack of nutrition and undergoes necrosis. Cerebral softening is, for this reason, the preserve of the diseases that affect the cerebral vessels and among these especially arteriosclerosis, of which it represents the most typical and overt manifestation. Arteriosclerosis of the cerebral vessels consists in an alteration of the vessel walls entailing the formation of islands of fatty substances (fatty degeneration), the deposition of calcium salts (atheromas), the loss of elastic tissue with secondary neoformation of connective tissue (sclerosis). The vessels become rigid, hard, their lumen ever less patent owing to the superimposition of atheromatous plaques or the formation of thrombi. The diminution of the blood supply to the cerebral parenchyma can be abrupt and extensive (as in the thrombotic occlusion of a large artery), and then there occur the large softenings that involve broad areas of cerebral tissue, whereas the more or less complete and gradual occlusion of the small vessels, sometimes diffuse throughout the whole brain, entails the formation of small diffuse multiple softenings, of small areas of atrophy around the vessels ("lacunar state").
The clinical symptomatology is essentially neurological (v. MALATTIE) and psychic; the latter is more pronounced and typical in the multiple softenings of generalized arteriosclerosis. The neurological symptoms are in close relation to the site of the softening: hemiplegias, hemianopsias, aphasias are frequent. Very often the foci of softening are bilateral, and then there occur certain symptoms clearly indicative of a bilateral lesion and which for this reason make the diagnosis very probable. Among these are cited the amimic facies with crises of weeping and spastic laughter, the disturbances of phonation and of swallowing, the gait with small steps ("pseudobulbar syndrome"). These disturbances generally become established gradually and are subject to aggravations and partial remissions.
The psychic symptomatology constitutes the picture of "arteriosclerotic dementia," whose main signs are hyperemotivity and the decline of the intellectual functions; the patient appears impressionable, irritable, prone to weeping, frequently distressed and depressed, also because of awareness of his condition. The memory of retention is electively disturbed, the recollection of recent acquisitions is lost, while remote facts can be remembered in minute detail.
The diagnosis generally presents no difficulty: the gradualness with which it becomes established can often (but not always) distinguish a paralysis from thrombotic softening from those sudden and dramatic ones due to cerebral hemorrhages (apoplectic ictus). Arteriosclerotic dementia is distinguished from senile dementia by the simultaneous presence of the neurological signs and because the latter presents with a global and uniform decline of all the psychic functions.
BIBL.: sources