Neurological Associations of COVID-19

Background: The COVID-19 pandemic, caused by SARS-CoV-2, is of a scale not seen since the 1918 influenza pandemic. Although the predominant clinical presentation is with respiratory disease, neurological manifestations are being recognised increasingly. Based on knowledge of other coronaviruses, especially those that caused the SARS and MERS epidemics, we might expect to see rare cases of central nervous system (CNS) and peripheral nervous system (PNS) disease caused by SARS-CoV-2. Recent developments: A growing number of case reports and series describe a wide array of neurological manifestations, but many lack detail, reflecting the challenge of studying such patients. Anosmia and ageusia are common, relatively specific for SARS-CoV-2 infection and may occur in the absence of other clinical features. Encephalopathy is relatively common, being reported for 16 (7.5%) of 214 hospitalised COVID-19 patients in Wuhan, China, and 40 (69%) of 58 in intensive care with COVID-19 in France. Encephalitis and Guillain-Barre syndrome have been described in case reports. SARSCoV- 2 is detected in the cerebrospinal fluid of some patients. Unexpectedly, acute cerebrovascular disease is also emerging as an important complication of severe disease, possibly due to a pro-inflammatory hypercoagulable state with elevated CRP, D-dimer, and ferritin. Where next? Careful clinical, diagnostic and epidemiological studies are needed to help define the manifestations and burden of neurological disease caused by SARS-CoV-2. Precise case definitions must be used to distinguish non-specific complications of severe disease, such as hypoxic encephalopathy and critical care neuropathy, from those caused directly or indirectly by the virus; these include infectious, para- and postinfectious encephalitis, hypercoagulable states leading to stroke, and acute neuropathies such as Guillain-Barre syndrome. Recognising SARS-CoV-2 neurological disease in patients whose respiratory infection is mild or asymptomatic may prove challenging, especially if the primary COVID-19 illness occurred weeks earlier. The proportion of infections leading to neurological disease will remain small. However these patients may be left with severe neurological sequelae. With so much of the population infected, the overall number of neurological patients, and their associated health, social and economic costs, may be large. Healthcare planners and policymakers must prepare for this eventuality.