Acute Necrotizing Encephalitis in Viral Respiratory Tract Infection: An Autopsy Case Report

Abstract

Acute necrotizing encephalitis (ANE) is a rare complication of viral respiratory tract infections, with specific histological changes. The condition is most commonly described in the pediatric population, however, it can also develop in the elderly, with some genetic factors being described as contributory. Herein, we report the autopsy finding of a patient with a viral respiratory tract infection, complicated with ANE. The patient was a 77-year-old female with multiple comorbidities living in a social home. For the two months prior, she had been hospitalized with cerebral infarction, respiratory tract infection, and exacerbation of chronic cardiac failure and concomitant hypertension and type 2 diabetes. On gross examination, the brain was edematous, with ground-glass opacity meninges a focus of encephalomalacia in the right cerebral hemisphere and multiple petechial hemorrhages. Histology revealed diffuse foci of encephalitis, with large areas of neuronal necrosis (coagulative-like necrosis) around the blood vessels and a sharp border with the surrounding healthy parenchyma - ANE. The patients tested negative for coronavirus disease 2019 (COVID-19).

Keywords: acute necrotizing encephalitis; morphology; pathology; respiratory tract infections.

Figure 1. Gross and histological changes in the trachea and lung

A: gross view of the trachea; B: histology of the trachea with desquamation of the respiratory epithelium, hyperemia, lymphocytic infiltrate and mucous hyperproduction, hematoxylin and eosin stain, original magnification x100; C: gross view of the lung; D: lung histology with hemorrhagic pneumonia, hematoxylin and eosin stain, original magnification x40; E: gross view of the lung on a cross-section; F: lung histology with hemorrhagic pneumonia, hematoxylin and eosin stain, original magnification x200. Note: gross images are obtained from the video recording

Figure 2. Epicardial histology

Epicardium with fibrosis and focal infiltration by lymphocytes, hematoxylin and eosin stain, original magnification 100x

Figure 3. Hemorrhagic changes in the spleen and liver

A: hemorrhagic areas in the spleen, hematoxylin and eosin stain, original magnification 40x; B: gross changes in the adrenal gland; C: histology from the adrenal glands with hemorrhagic areas, hematoxylin and eosin stain, original magnification 100x

Figure 4. Acute necrotizing encephalitis on histology

A: acute necrotizing encephalitis with neuronal necrosis (coagulative-like necrosis), neurophagia and reactive gliosis, Hematoxylin and eosin stain, original magnification 40x; B: higher magnification view of the perivascular changes with lymphocytic infiltration and degenerative and necrotic neurons, hematoxylin and eosin stain, original magnification 100x; C: the border with healthy brain parenchyma, Hematoxylin and eosin stain, original magnification 100x; D: neuronal necrosis with cellular debris and scant inclusions, hematoxylin and eosin stain, original magnification 400x. Note: blue lines on A and C depict the border between the necrotic tissue and the healthy parenchyma

Figure 5. Pharyngeal smear cytology

Excessive asymmetrical perinuclear granulations in superficial squamous epithelial cells from the pharynx, modified Nissl’s stain (Cresyl violet), original magnification 400x