Polioencephalitis

POLIOENCEPHALITIS (from the Greek polios—gray and encephalon—brain), inflammation of the gray matter of the brain, i.e., a specific case of encephalitis. The term was first introduced by Wernicke (1881) to designate a disease that does not, in essence, represent an inflammatory process; Wernicke's "acute hemorrhagic polioencephalitis" is apparently a vascular disease, but subsequently this term began to be applied to inflammatory diseases as well, with a distinction made between upper acute polioencephalitis, with the localization of the process in the gray matter of the cerebral peduncles (midbrain), and lower acute polioencephalitis, with the localization of the process in the gray matter of the pons and medulla oblongata. In 1884, Strümpell expressed the view that many cases of so-called infantile cerebral palsy have polioencephalitis as their basis, i.e., inflammation of the gray matter of the brain; in doing so, Strümpell drew an analogy between polioencephalitis and poliomyelitis in the sense that polioencephalitis represents the result of the localization in the cerebral cortex of the very same process which, when localized in the gray matter of the spinal cord, leads to the picture of acute anterior poliomyelitis. Subsequent observations fully confirmed the point of view expressed by Strümpell: during epidemics of Heine-Medin disease, various forms of brain involvement were repeatedly observed alongside spinal forms, and one of the main reasons for introducing the term "Heine-Medin disease" was the circumstance that the previously used term "acute poliomyelitis" contained the concept of only one variety (spinal) of this disease, which can be localized in any part of the central nervous system; and since Heine-Medin disease can be observed not only epidemically but also sporadically, there are all grounds to assert that at least some cases of polioencephalitis, i.e., cases of inflammation of the gray matter of the brain in the absence of any obvious infection, represent sporadic manifestations of Heine-Medin disease. There is no doubt, however, that acute polioencephalitis can be caused not only by the virus of Heine-Medin disease but also by other infections, among which the main place belongs to scarlet fever, measles, typhus, and influenza. It must be admitted that the term polioencephalitis contains a certain inaccuracy: by its very nature, an inflammatory process, representing a diffuse rather than a systemic lesion, cannot be strictly limited to the gray matter alone; almost always in diseases designated by the term "polioencephalitis," there is a more or less clear involvement of the white matter in the process as well. This correction is fully appropriate in relation to Wernicke's disease (acute superior hemorrhagic polioencephalitis, polioencephalitis haemorrhagica superior), in which hemorrhages are also not limited to the gray matter of the midbrain (see below). Isolated lesions of the gray matter are observed not in inflammatory processes, but in primary systemic degenerations. Some authors have applied the term "polioencephalitis" to this type of disease as well, designating them as "chronic polioencephalitis." Thus, van Gehuchten and others designate chronic progressive ophthalmoplegia with the term "chronic superior polioencephalitis," and progressive bulbar palsy with the term "chronic inferior polioencephalitis." Such an application of the term "polioencephalitis," which contains the concept of an inflammatory process, to diseases that are known not to have an inflammatory character, hardly deserves imitation. The application of the term "polioencephalitis" to progressive degenerations of the nuclei of the brainstem and the nuclei of the medulla oblongata should also be considered inappropriate. If one proceeds from the analogy with poliomyelitis, then, of course, one can speak of acute and chronic polioencephalitis. Thus, it would be expedient to retain the term "polioencephalitis" only for acute inflammatory lesions of the brain, with the proviso, however, that in the majority of these cases, contrary to the precise meaning of the word polioencephalitis, the matter concerns a predominant, rather than exclusive, lesion of the gray matter. In this sense, epidemic or lethargic encephalitis (see Encephalitis) could also be included in the group of polioencephalitis, in which pathological-anatomical observations also indicate a predominant lesion of the gray matter (nuclei of the diencephalon and midbrain); but this disease is distinguished, as is known, as an independent nosological form and is not designated by the term "polioencephalitis." Thus, the term "polioencephalitis" is currently applied, firstly, to acute inflammatory processes with a predominant localization in the gray matter of the brain and, secondly, to Wernicke's disease (acute hemorrhagic polioencephalitis), the inflammatory nature of which can be disputed not without reason. These two groups of diseases are kept in mind below. Acute infectious polioencephalitis is observed mainly in childhood and arises either on the basis of various infectious diseases (see above) or as a primary infection of the brain; in this latter case, it is most often a matter of sporadic forms of Heine-Medin disease. Most often, the process is localized in the cerebral cortex, leading clinically to the picture of infantile cerebral palsy (Strümpell's form). The disease begins acutely, with a rapid rise in temperature to 39–40° and general symptoms of brain disease (headache, delirium, general or Jacksonian epileptic seizures). Symptoms from the meninges are either absent or not clearly expressed. Very soon, a more or less sharply defined paralysis appears, usually in the form of hemiplegia, accompanied by rigidity and contractures. The disease may end in death in the acute period; more often, however, recovery is observed, or rather recovery with a defect, i.e., with persistent paralysis of the central type. Along with hemiplegia or without it, other losses of cortical functions may be observed: aphasia, hemianopsia, pseudobulbar palsy; sometimes inflammatory changes are localized exclusively or predominantly in the cerebellar cortex, leading to the external clinical picture of acute cerebellar ataxia. In those cases where the inflammatory process affects the nuclei of the midbrain, the clinical picture is expressed by paralysis of the eye muscles (oculomotorius—ophthalmoplegia). Such forms were observed during epidemics of Heine-Medin disease, but also in the form of sporadic cases. By their main clinical manifestations (paralysis of the eye muscles), such forms of polioencephalitis are similar to Wernicke's disease, and the term "polioencephalitis superior acuta" would be fully applicable to them. But in view of the fact that the concept of Wernicke's hemorrhagic encephalitis has long been associated with this term, it would be possible (as Wickman suggests) to distinguish two forms of upper acute polioencephalitis: hemorrhagic (Wernicke) and inflammatory, which Wickman proposes to designate by the term "acute superior polioencephalitis—Medin form," named after Medin, who first described this form. This form differs significantly from the Wernicke form. The latter has an afebrile course but is accompanied by mental disorders. On the contrary, the Medin form is characterized by a sharply febrile course, consciousness is impaired, and there is delirium. In its essence, it represents an infectious inflammatory lesion of the motor nuclei of the brainstem. In those cases where, during various infectious diseases, the inflammatory process affects the nuclei of the pons and medulla oblongata, which is manifested clinically by atrophic paralysis of the V–XII cranial nerves, one speaks of lower acute polioencephalitis; as a synonym for this term, some use the term "acute bulbar poliomyelitis." One of the most characteristic symptoms of such a localization of the inflammatory process is atrophic paralysis of the tongue (see Glossoplegia), which can be unilateral or bilateral. Both upper and lower polioencephalitis are often combined with a lesion of the pyramidal tracts, which leads to the picture of more or less clearly expressed alternating paralyses. Pathologically, the area affected by polioencephalitis appears on cross-section as dark red, slightly protruding above the surface of the section, and edematous; microscopically, sharp infiltration of the perivascular spaces and adjacent sections of the brain substance is established; many of the smallest vessels, especially veins, become thrombosed, the consequence of which are the smallest foci of softening and punctate hemorrhages. In the areas of such softening, complete necrosis of the tissue is observed, but the death of nerve cells also takes place in areas of purely inflammatory changes, where sharply expressed phagocytosis, neuronophagia, and the appearance of "granular cells" are observed; in the nerve fibers, swelling of the myelin sheaths occurs with subsequent disintegration of myelin into separate clumps and its gradual disappearance. Glial elements, which disintegrate in areas of complete softening, show sharp phenomena of proliferation in the periphery and in the foci of inflammatory changes. The final result of all these changes is the formation of a glial scar; in cases of significant foci of thrombotic softening, cysts may also form in the places of former polioencephalitic foci.

Gliotic scars and cysts can subsequently serve as the cause of Jacksonian or generalized epileptic seizures, with which, as is known, so-called infantile cerebral palsies are often complicated. The diagnosis of polioencephalitis is based on the acute development of cerebral symptoms with elevated temperature. One should beware of confusion with meningism, often observed in children during acute infectious diseases. The distinction from meningitis is based on the examination of the cerebrospinal fluid, which in polioencephalitis either presents no pathological changes or reveals only insignificant lymphocytosis; phenomena of meningeal irritation (Kernig's sign, stiffness of the neck muscles) may be present in polioencephalitis, but they never reach such severe degrees as happens in meningitis. Brain abscess usually proceeds without fever or fever is observed only for a short time; the pulse in abscess is slowed; choked discs in abscess can be observed not infrequently, while in polioencephalitis they are as a rule absent. An abscess develops in the presence of a purulent focus in the vicinity (suppuration of the accessory sinuses, osteomyelitis of the cranial bones, trauma to the skull) or a source for cerebral embolism (lung abscess); polioencephalitis develops without a visible cause (Heine-Medin forms) or as a complication of acute infectious diseases (scarlet fever, measles, etc.). A topical diagnosis is established on the basis of the typicality of the clinical symptom complex. The diagnosis of a past polioencephalitis in the presence of its consequences in the form of infantile cerebral palsy is based on anamnestic indications of the onset of this disorder after an acute febrile illness with cerebral symptoms in a child who had previously developed correctly and had not shown any paralytic phenomena. Other forms of infantile cerebral palsy differ from polioencephalitic ones in their development and course. Infantile palsies depending on agenesis and intrauterine brain lesions are observed from birth; the same applies to traumatic brain injuries during the act of birth and asphyxia. Atrophic sclerosis has a chronically progressive course. Regarding superior hemorrhagic polioencephalitis of Wernicke, enough was mentioned above. This name is retained for this disease more by tradition than by strict correspondence to its nature. Firstly, Wernicke's polioencephalitis represents a toxic (alcoholic) disease, and not an inflammatory one, and secondly, the localization of hemorrhages in this disease is not limited to the gray matter of the midbrain, but is also observed in other parts of the central and peripheral nervous system. Regarding prognosis, all forms of acute polioencephalitis must be considered as very serious diseases, threatening death in the acute period, and in case of recovery, leaving persistent functional deficits. In a certain number of cases, besides the loss of motor and sensory functions, there are various degrees of mental defects; epilepsy in the form of cortical or generalized seizures is also not infrequently a consequence of past polioencephalitis, and sometimes epilepsy develops only 2-3 years after the acute period of the disease. The degree of functional loss and the possibility of their recovery over time is determined by a number of different factors, such as: the age of the patient, the degree of encephalitic destruction of the brain, their localization; only in rare cases does polioencephalitis leave behind consequences that, in their insignificance, border on complete recovery. The treatment of polioencephalitis, insofar as it concerns acute infectious forms, is limited to symptomatic measures: rest, urotropine intravenously, salicylic preparations, bromine. If hopes for serum treatment of Heine-Medin disease are justified, then its use may prove appropriate also in encephalitic forms of this disease; the question of the effectiveness of this serum should be considered as yet unresolved. Sporadic cases of Heine-Medin disease in the form of polioencephalitis represent diseases appearing in isolation in the form of single cases, and in this sense cannot be the subject of prophylaxis. However, each such case must attract attention as a threat of an incipient epidemic, and upon the appearance of repeated cases, depending on the frequency and degree of their spread, it is necessary to take appropriate measures: isolation of patients, closing of schools, cessation of gatherings of children, etc.; for those around a patient with primary polioencephalitis, especially children, gargling of the throat with a 1% solution of hydrogen peroxide or 1:5,000 (1 teaspoon of 1% solution per glass of water) potassium permanganate is recommended. The prophylaxis of polioencephalitis, which is a complication of various infectious diseases, is exhausted by the prophylaxis of the latter. Statistics for polioencephalitis do not exist, which is quite understandable if one takes into account that the forms attributed to this group appear to be unequal in their nature, and the latter cannot always be established during life. Until now, it cannot be considered resolved whether all cases of primary polioencephalitis represent a manifestation of Heine-Medin disease or if other forms of primary polioencephalitis are possible. As for secondary polioencephalitis, their number in relation to the frequency of acute infectious diseases, of which they are a complication, turns out to be very insignificant.