Encephalitis

ENCEPHALITIS. - In an absolute sense, the term should indicate exclusively the morbid processes of an inflammatory nature that affect the mass of the encephalon, whether in the gray matter (polioencephalitis) or in the white matter (leukoencephalitis or demyelinating e.). In practice, the term e. is used generically to indicate forms in which the causal element may not be infectious and the anatomopathological lesions are not properly those classic to inflammation; in these, toxic factors operate, or the action of a virus is not demonstrable and only presumptive; for these, the expression "pseudoencephalitis" or "encephalosis" would be more exact.

Such uncertainty and impropriety of terms is an indication of the frequent difficulty of bringing the causal element to light and of e. sometimes presenting itself as a secondary manifestation in the course of various infectious morbid processes (direct action of the virus and its toxins), of exogenous intoxications (alcohol, lead, medications, etc.) or endogenous ones due to altered metabolism (diabetes, nephritis, toxemias of pregnancy, avitaminosis, dysendocrinias, etc.). E. can develop in an acute or hyperacute form, such as to cause death in 1-2 days (epidemic e.) or with a chronic course and progressive symptomatology. In relation to the high anatomical and functional dignity of the tissue affected, e. is always accompanied, more or less, by nervous symptomatology (anesthesias and paralyses corresponding to the topography of the foci, particularly in the circumscribed purulent forms of cerebral abscesses), or even psychic symptomatology with diminution or complete deficit of consciousness (v. coma), or partial impairment of the various elementary activities that constitute it and of which they are the manifestation (interest, attention, perception, memory, intelligence, will, affectivity), or of moral character. Particular damage is inflicted, beyond nervous functionality, on the psychic personality of the individual, if the e., particularly if associated with meningitis, developed during the fetal and infantile period of life; in such cases, the encephalon in the course of evolution suffers impairments and arrests of development sometimes so slight as to be poorly demonstrable from the anatomopathological point of view, yet always such as to produce true psychoses (v. PRENASTENIA). Such "mentally deficient" individuals are worthy of the greatest consideration, not only from the medical point of view but also from the educational, juridical, and moral points of view, being susceptible to treatment, partial recovery, and social utilization, albeit on a plane of lesser values. In adults, with encephalic development by then complete and an acquired ideational patrimony, mental damage of greater or lesser severity may occur, up to complete dementia (v.), as, for example, in progressive paralytic dementia (v.).

Of particular importance from the practical point of view (familial, social, pastoral) is knowledge of the neuropsychic picture that develops as a sequel of a particular form: epidemic or lethargic e. (Economo's disease), which, in its phase of chronicization, takes the form of so-called "post-encephalitic parkinsonism." In it, to the ocular and extrapyramidal phenomena (strabismus, spasms, hypertonicity of the muscles with slow and impeded movements), to the neurovegetative disturbances (altered metabolism and endocrine balance), there is added a particular neurastheniform and hysteroid psychic picture, an exaggerated emotionality, a particular slowness, difficulty in understanding, at times an appearance of incomprehension, such as to make the individual appear affected by catatonia or dementia. On the contrary, in the majority of such patients the intelligence is not substantially altered, memory, perception, ideation, and discriminative powers are nearly normal, even though such activities are carried out with a characteristic slowness (bradypsychism) similar to that which makes the movements of the body slow and laborious. All authors agree in admitting that, however accentuated the cerebral torpor may be, however slow the psychic reaction and the capacity to fix new perceptions, however serious the impediment, and therefore the externalization of the volitional powers and affective manifestations, in post-encephalitic parkinsonism there does not exist a true mental defect, and therefore there does not exist a true post-encephalitic dementia (G. Moglie, op. cit., p. 660).

Giuseppe de Ninno