A case of limbic encephalitis with CSF detection of sars-cov2 virus: Immune-mediated mechanism or direct viral damage?

Braccia, Arianna; Carta, Francesca; Fiorillo, Domenico; Tecilla, Ginevra; Cesnik, Edward; Fallica, Elisa; Govoni, Vittorio; Cultrera, Rosario

Background and aims: Pathogenesis of neurologic syndromes COVID 19-related could be categorized in four mechanisms: direct viral damage, para/post-infectious effect, complications of prolonged illness. We present a case of limbic encephalitis (LE) with concurrent detection of SARS-CoV2 virus in cerebrospinal fluid (CSF), which makes the individuation of a unique etiological mechanism insidious. Methods: A 70-year-old man was hospitalized with respiratory symptoms and confusional state. A chest CT-scan and nasopharyngeal swab demonstrated COVID-19 infection;non contrast brain CT-scan was unremarkable. Neurological examination revealed right focal signs and vigilance fluctuations;EEG showed nonspecific mild background activity slowing, basic CSF investigations resulted negative and total-body CT-scan excluded tumours. Brain MRI showed T2-FLAIR hyper intensity in the mesial temporal lobes, strongly supporting the hypothesis of limbic encephalitis. So the patient underwent to a second lumbar puncture to test the autoimmune panel (negative). [Formula presented] [Formula presented] Results: Liquoral PCR for SARS-CoV2 RNA resulted positive. After treatment with 5 days- IV bolus dose of metilprednisolone and a cycle of IV immunoglobulin therapy, he had a slight improvement, especially concerning alertness and cognition. Two months follow-up brain MRI was superimposable to the precedent. [Formula presented] Conclusions: Majority of cases of LE with positive testing for specific antibodies are negative for RT-PCR for SARS-CoV2 tested on LCR (1). In this case, the presence of the virus in CSF supports a direct neural damage;conversely, the answer to immunomodulant treatment could suggest an immunological role;previous autopsy results of patients with SARS-COV1 (2) evidenced the presence of viral RNA in brain tissue, particularly accumulating in and around the hippocampus. 1. Lerzan Dogana, Dilaver Kayab, Tugce Sarikayaa, Rehile Zenginc, Alp Dincerd, et al. Plasmapheresis treatment in COVID19 related autoimmune meningoencephalitis: Case series. Brain, Behavior, and Immunity 87 (2020) 155–158 2. Gu J, Gong E, Zhang B, et al. Multiple organ infection and the pathogenesis of SARS. J Exp Med. 2005;202: 415–424.