Post-COVID-19 autoimmune encephalitis rare
Autoimmune encephalitis occurred occasionally among a cohort of patients after having had COVID-19, according to study results published in Neurology.
“The frequency of autoimmune encephalitis (AE) associated with SARS-CoV-2 is unknown,” Cristina Valencia-Sanchez, MD, PhD, of the department of neurology at Mayo Clinic in Minnesota, and colleagues wrote. “In this study, we aimed to evaluate the frequency of SARS-CoV-2 antibodies in sera of patients who underwent neural antibody testing as part of the diagnostic evaluation for AE at Mayo Clinic in Rochester, Minnesota, during 2020, and report AE cases occurring post-COVID-19.”
The researchers used a chemiluminescence assay authorized by the FDA to test for total antibodies against the SARS-CoV-2 spike glycoprotein in the residual sera of 556 consecutive patients who received autoimmune encephalopathy neural IgG assessment. They reviewed clinical records from patients who tested positive for SARS-CoV-2 antibodies and had available research consent. They also cross-referenced with an encephalopathy cohort of 31 individuals for cases that met AE diagnostic criteria.
Results showed positive SARS-CoV-2 antibody test results among 18 (3%) participants in the laboratory cohort. Diagnoses were two AE, three post-acute sequelae of SARS-CoV-2 infection, two cases of toxic metabolic encephalopathy during COVID-19 pneumonia, nine diverse non-COVID-19 relatable neurological diagnoses and two unavailable. Valencia-Sanchez and colleagues reported AE among five (16%, which included two overlapping laboratory cohort cases) of the encephalopathy cohort, which represented 0.05% of the 10,384 patients diagnosed and cared for with any COVID-19 illness at the clinic in 2020.
One patient met definite, one met probable and three met possible AE diagnostic criteria, with median symptom onset age of 61 years. These five patients were neural IgG negative, and four tested were SARS-CoV-2 PCR/IgG index negative in cerebrospinal fluid.
The researchers noted diverse phenotypes and accompanying MRI and EEG findings, with delirium in five, seizures in two, rhombencephalitis in one, aphasia in one and ataxia in one. They observed no cases of acute disseminated encephalomyelitis. Syndromes spontaneously resolved among the three patients with possible AE. One patient with definite limbic encephalitis had residual mood and memory problems, despite being immune therapy responsive. One patient with probable autoimmune rhombencephalitis who received immune therapy died. The researchers noted toxic-metabolic diagnoses among the remaining 26 encephalopathy cohort patients.
“Given the usual absence of disease-specific IgG markers in postinfectious AE, future studies should focus on systematic collection of serum, peripheral blood mononuclear cells and CSF to investigate for diagnostically and pathophysiologically informative cellular and cytokine signatures,” Valencia-Sanchez and colleagues wrote.