Two forms of acute non-suppurative encephalitis may be said to exist clin ically, according to the extent and dis tribution of the inflammatory process.
Acute focal encepha litis means a more or less circumscribed arca in one lobe, or a number of inflam matory foci grouped together in one lobe or region of the brain.
Acute diffuse encepha litis may affect an entire lobe or hemi sphere, or both hemispheres.
Acute disseminated encephalitis is so rare an affection that no clinical type can be described.
Symptoms.—The symptoms of acute non-suppurative encephalitis vary in their character according to the extent and intensity of the process, the cause producing the inflammation, and the particular region affected. In certain eas.es, however, the post-mortem cxami tion failed to reveal lesions commen surate with the symptoms during life; and the conclusion has been reached that, especially in those cases of acute non-suppurative encephalitis following influenza, typhoid fever, and the acute infections generally, there is a toxic ele ment which not only intensifies the symptoms due to organic lesions also present, but is capable of causing a fatal termination in cases which after death may show comparatively-slight lesions. This intensification of the symptoms due to the primary toxternia, may explain the rapid and complete recoveries which at times occur in the paralytic phenomena in such cases. Few cases, however, pass ' through an attack of acute encephalitis without some lasting mental or physical I defect. The symptoms of acute non suppurative encephalitis will be de scribed according as the disease is focal or diffuse, although they have many symptoms in common.
(a) Acute focal non-suppurative en cephalitis occurs most frequently in children, but cases are reported in adults, especially after influenza, and in alco holics. The onset is usually sudden: after or during an attack of sonic acute infectious disease of childhood, or after influenza, diphtheria, typhoid fever, or, more rarely, after traumatism; there are headache, vomiting, fever, convul sions (single or repeated), irritability, and restlessness, with a tendency toward hebetude, or stupor. There may be an initial chill, or repeated chilly sensations may be complained of by the patient. When the disease arises during the course of some acute infectious disease the significance of the symptoms may be easily overlooked, or attributed to men ingitis, until some form of paralysis makes the nature of the case clearer.
The typical case, however, runs a more or less irregular course. Drowsiness is usually an early and a very characteristic symptom, and this encephalonarcosis may persistently deepen, especially in rapidly-fatal cases, or it may alternate with periods of restlessness and delirium. In nearly all cases mental obtuseness is present, and in some cases there is also marked confusion of ideas, which may persist after the acute symptoms have passed away. The convulsions may be toxic or chronic, local or general, and are not characteristic of anything, dur ing the aeute stage, except as denoting a cerebral irritation. Rigidity of the spinal muscles and opisthotonos may occur, but the latter is much less fre quent than in meningitis. The fever runs a moderate course, rarely exceed ing 103° F. and subnormal variations are not uncommon, especially during the comatose states, which generally super vene rapidly after the acute onset. Dur ing the acute progress of the disease some form of paralysis may be noticed, or it may be almost the first sign in certain cases (see case reported by Put nam in the Journal of Nervous and Mental Diseases, '97), which_ begin usu ally less acutely than these eases oc curring in connection with the acute infectious diseases. In other eases oc curring during the height of an acute infectious disease, the paralysis may remain unnoticed until convalescence is well established, and the diagnosis of the case thus disclosed. The paralysis may take any form, and sensation may be affected, althongh few observations of this kind are on record. The paralysis may or may not be attended by spasm of the affected muscles. Atrophy is usu ally of limited degree when present at all, and Spitzka has observed hyper trophy of certain paralyzed muscle groups. The location of the inflamma tion determines the form of the reNlting paralysis. In the type of acute encepha litis described by Strlimpell in 18S4, and considered by him as strictly anal ogous to infantile poliomyelitis and the bulbar type of polioencephalitis de scribed by Wernicke, it has since been found that the lesions quite commonly involve the white substance as well as the cortex. For this reason the writer COITCHTS with Mills that the term "cor tical encephalitis," while true of certain cases, is not as good as focal encepha litis, which can include all of these acnte intracercbral inflammations, whether cortical, subcortical, or basal in location.