Pathology and pathogenesis of viral infections of the central nervous system

Histopathology and immunohistochemistry of bats infected by Australian bat lyssavirus

OBJECTIVE

To describe the lesions and distribution of viral antigens in bats infected by Australian bat lyssavirus.

DESIGN

A retrospective histopathological and immunohistochemical study of bats naturally infected with the virus.

PROCEDURE

Tissues from 37 infected bats were examined. Nineteen flying foxes (fruit bats) and two insectivorous bats were examined in detail. Brains of another 16 flying foxes were poorly fixed and were examined less fully.

RESULT

Lesions varied considerably between individuals and, where present, were mostly those of nonsuppurative meningoencephalomyelitis and ganglioneuritis similar to lesions seen in rabies and rabies-like diseases. The number of cells with intracytoplasmic inclusion bodies (Negri bodies) was variable; none were seen in some bats. Intracytoplasmic vacuolation of neurons was a common finding. Lesions occurred throughout the central nervous system but were most frequent and severe in the hippocampus, thalamus and midbrain, and medulla oblongata and pons. Indirect immunoperoxidase tests for lyssavirus antigen reactions varied in intensity and distribution, but also occurred mostly in the hippocampus, thalamus and midbrain, and medulla oblongata and pons. In peripheral tissues, reactions were seen in autonomic ganglia, in nerve plexuses of the gastrointestinal tract, in nervous tissues within muscles and immediately adjacent to individual muscle fibres, in an adrenal medulla, and in epithelial tissues in one of eight salivary glands examined.

CONCLUSION

The main lesion in Australian bat lyssavirus infection is nonsuppurative inflammation similar to that seen in rabies and other rabies-like diseases, except that the number of Negri bodies is more variable. Reactions to immunoperoxidase tests for lyssavirus vary in intensity and distribution and may occur in both central and peripheral nervous systems. These reactions do not always occur in the salivary glands, even if brain infection is present.

[Disseminated herpetic encephalitis: report of an autopsy case with immunohistochemical study]

An autopsied case of disseminated herpetic encephalitis in a previously healthy one-year-and-three-month-old child is reported. He had fever, repeated convulsive crises and alterations of consciousness which progressed into a coma, leading to death in eight days. The neuropathological picture was characterized by necrosis and inflammation in multiple foci disseminated in the cerebral hemispheres, brainstem and cerebellum. The Avidin-Biotin-Peroxidase Complex technique showed, in neurons of the thalamus, intra-cytoplasmatic immunoreactivity, and, very rarely, intranuclear for the Herpes simplex virus type 1 antigens. This case differs from the other herpetic encephalitis ones described in the literature in two aspects: (1) by the dissemination of the lesions, in contrast with the forms topographically limited to the limbic system and, less commonly, to the brainstem; (2) by the presence of necrosis, inflammation and focal hemorrhage, which are alterations that practically do not exist in cases of disseminated encephalitis typically described in immuno-depressed individuals.

[Acute diffuse lymphocytic meningoencephalitis: a clinico-pathological report of a case]

A clinicopathologic case of acute diffuse lymphocytic meningoencephalitis in a 8-year-old child is reported. Clinical picture started 7 days prior to death and was characterized by fever and occipital cephalea followed by worsening of general conditions, vomiting and generalized convulsive crisis together with cardiopulmonary arrest and coma. The pathologic examination showed alterations only in the brain, namely pronounced cerebral edema and inflammatory infiltrate, predominantly lymphocytic, perivascular, particularly in the white matter, in all regions analyzed. This case is compared to the ones described in the literature and the etiopathogenesis of acute diffuse lymphocytic meningoencephalitis is discussed. The necessity of making public cases of non-bacterial acute encephalitis is emphasized, due to the fact that most of them remain with undetermined etiology.

[Virologic studies in patients with amyotrophic lateral sclerosis]

The effects of intracerebral inoculation of cerebrospinal fluid in mice from 9 patients with amyotrophic lateral sclerosis are reported. There were 704 animals inoculated. The results were considered positive when the animals presented difficulties in walking and equilibrating. Cases 1, 2, 6, 7 and 9 were positives in the first passage. In case 1, the positivity was reached from first to fourth passage and in case 6, to third passage. At sight of this results, the possibility of that disease to be caused by slow-virus is discussed.

Fatal herpes simplex encephalitis with demonstration of virus in the olfactory pathway

A fatal case of herpes simplex encephalitis contained viruses within the olfactory pathway but not in the trigeminal ganglia. This finding supports the theory that the olfactory nerves are the portal of entry in adult herpes simplex encephalitis.

New phenotypic variant of adrenoleukodystrophy. Pathologic, ultrastructural, and biochemical study in two brothers

Adrenoleukodystrophy is not usually considered in the differential diagnosis of the infantile onset of failure to thrive with motor and intellectual retardation. Rather, symptoms have started in childhood and have progressed over some years; not all patients have had overt adrenocortical insufficiency. The two brothers reported here developed symptoms in the neonatal period. In each the nature of the primary cerebral disorder was not recognized, because other etiologic factors clouded the diagnostic studies. In the younger brother, Case 1, a high titer (1:256) for cytomegalovirus (CMV) led to the suspicion that CMV infection accounted for the neurologic and ophthalmologic findings. Progressive neurologic deterioration at the age of 6 years prompted brain biopsy to confirm the diagnosis of progressive CMV encephalitis. In the older brother, Case 2, hemogenic hydrocephalus due to traumatic birth injury was held responsible for the psychomotor retardation and cerebral palsy. At necropsy, the adrenal glands in both cases were severly atrophic. In Case 1, a markedly inflammatory leukodystrophic process affected chiefly the frontal centra semiovalia and internal capsules, with relative sparing of parieto-occipital white matter and subcortical U-fibers. Heavy lymphocyte and monocyte cuffs surrounded many blood vessels in the white matter, and oil-red-O and PAS-positive macrophages were scattered in the zones of myelin disintegration and loss. Focally, the leukodystrophic process was so intense that cavitation necrosis was present, especially in the internal capsules. Further, PAS-positive, striated macrophages were aggregated in large clusters in liver, spleen, and lymph nodes. At the ultrastructural level, linear and gently arced, parallel, coapted or widely separated leaflets measuring 3-4 nm in width were identified in macrophages of the brain biopsy and in autopsy liver and lymph node. Biochemical analysis of fresh, frozen autopsy brain demonstrated cholesterol esters with long-chain fatty acids by thin-layer and gas-liquid chromatography. In Case 2, the leukodystrophic process could be readily identified in the brainstem and cerebellum but was masked in the cerebral hemispheres by the extensive hydrocephalus. The adrenal glands were atrophic and at light microscopy revealed adenomatoid nodules, many ballooned coritcal cells and very rare cells with striated cytoplasm. Masses of PAS-positive macrophages were encountered in liver and lymph nodes. In both cases, only old Wallerian degeneration of the corticospinal tracts was found in the spinal cord.

Distribution of herpes simplex virus in acute necrotising encephalitis

A 49-yr-old female developed a rapidly progressive neurological illness. The gross, light microscopic and electron-microscopic examination of the brain revealed all of the characteristic features of acute necrotising encephalitis with predominant involvement of the left limbic system. The distribution of herpes simplex virus suggests that the olfactory apparatus is the route of infection.

The gangliosidoses: comparative features and research applications

Ganglioside storage diseases are inherited defects of lysosomal hydrolases that result in intralysosomal accumulation of gangliosides and other complex metabolites. Gangliosidoses occur in man, cats, cattle, dogs and swine. In all species, these diseases are characterized clinically by relentlessly progressive neurological deterioration. Lysosomal hypertrophy with characteristic ultrastructural inclusions occur in neurons, endothelial and other cells. Definitive diagnosis requires biochemical identification of the storage product and enzyme deficiency. Gangliosidoses in animals are important models of human lysosomal diseases and may be a significant complication in the maintenance of certain purebred stocks of domestic animals.