LUST, Mdbnch. Med. Voch., lxxiv, 1927
- Ergebo. Inn
The term 'encephalitis' signifies in the most general manner an 'inflammation' of brain substance, (lue to activity of microorganisms , viruses, or toxins. It is in common usage for a large and heterogeneouis variety of conditions, to not all of which can it legitimately be applied. Recent controversies have shown up prominently the uncertainties surrounding the conception of 'inflammation' itself, hence ' encephalitis ' is doubly suspect. The o0l cardinal signs of rubor, calor, tumor, and dolor cannot be regarded as tvpical of inflammation in the neuiraxis; today their place is taken, in respect of the nervous system, by parenchymatous (ectodermal) changes and bv exudative, infiltrative, and proliferative reactions on the part of the mesoderm (vascular and connective tissues) ; an(l these features of histological response to foreign irritants undoubtedly constitute a kind of anatomical definition commanding general acceptance. But perplexities begin as soon as we try to discover the meaning of individual tissue-reactions or draw etiological concluisions from the histological syndrome. Even if we restrict the expression 'encephalitis ' to cases with recognisable mesodermal processes, no specificity attaches to their etiology; on the contrary, disease-conditions that are conspicuously diverse on the clinical side (such as poliomyelitis, epidemic encephalitis, rabies, neurosyphilis, nevertheless resemble each other more or less closely as far as conjunctivo-vascular tissue-response is concerned, though alterations of the neural parenchyma may be less uniform; moreover, one and the same toxi-infection often enough exhibits notable histological variations in different instances (cf. epidemic encephalitis without obvious 'inflammatory' evidence), and, there is reason to believe, at different stages of the same case. With such infections as tetanus, diphtheria , or typhoid fever parenchymatous change is paramount and mesenchymal modifications often negligible, or even absent. From the standpoint of pathological anatomy it seems possible to distin-guiish several types of tissue-reaction all of which still pass under the heading encephalitis '.and emphasise afresh its indeterminate nature.