Table 1.

Definition of COVID-19-related neurological complications based on WHO and Ellul et al.10

SARS-CoV-2 meningitis, encephalitis, myelitis, or CNS vasculitis*
Confirmed	SARS-CoV-2 detected in CSF or brain tissue or evidence of SARS-CoV-2-specific intrathecal antibody No other explanatory pathogen or cause found
Probable	SARS-CoV-2 detected in respiratory or another non-CNS sample or evidence of SARS-CoV-2-specific antibody in serum indicating acute infection. No other explanatory pathogen or cause found
Possible	Patient meets the suspected case definition of COVID-19 according to national or WHO guidance based on clinical symptoms and epidemiological risk factors; in the context of known community SARS-CoV-2 transmission, supportive features include the following: the new onset of at least one cough, fever, muscle aches, loss of smell, or loss of taste; lymphopenia or raised D-dimer level; and radiological evidence of abnormalities consistent with infection or inflammation (e.g., ground glass changes)
Acute disseminated encephalomyelitis associated with SARS-CoV-2 infection, Guillain-Barré syndrome, and other acute neuropathies associated with SARS-CoV-2 infection.
Probable association	Neurological disease onset within six weeks of acute infection Either SARS-CoV-2 RNA detected in any sample or antibody evidence of acute SARS-CoV-2 infection No evidence of other commonly associated causes
Possible association	Neurological disease onset within six weeks of acute infection Either SARS-CoV-2 RNA detected in any sample or antibody evidence of acute SARS-CoV-2 infection Evidence of other commonly associated causes

Abbreviations: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; COVID-19, coronavirus disease 2019; WHO, World Health Organization.