COVID-19-associated necrotizing encephalopathy presenting without active respiratory symptoms: a case report with histopathology

Acute necrotizing encephalopathy (ANE) is a rare complication of coronavirus disease 2019 (COVID-19) secondary to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The condition is typically diagnosed based on characteristic neuroimaging findings in the context of active viral respiratory symptoms. We present a rare case of COVID-19-associated ANE presenting with expressive aphasia and encephalopathy in the absence of active respiratory symptoms. Initial evaluation revealed bilateral thalamic lesions and a mild neutrophilic-predominant pleocytosis on cerebrospinal fluid analysis, the latter of which has not been described in previously published cases. Presence of these atypical features prompted extensive diagnostic evaluation. Metagenomic next-generation sequencing on cerebrospinal fluid did not detect the presence of pathogenic nucleic acids. Thalamic biopsy revealed perivascular neutrophilic inflammation suggestive of small vessel vasculitis with surrounding hemorrhage and necrosis. Ultimately, the diagnosis was made following detection of SARS-CoV-2 serologies and after exclusion of alternative etiologies. The patient was successfully treated with a short course of high-dose methylprednisolone with favorable outcome.