Altered mental status in COVID-19

BACKGROUND: Altered mental status (AMS) is a common neurological manifestation of COVID-19 infection in hospitalized patients. The principal causes of AMS have yet to be determined. We aimed to identify the common causes of AMS in patients with COVID-19 presenting to the emergency department with AMS on arrival. METHODS: We conducted a retrospective observational study of patients presenting with AMS to three New York hospitals, from March 1 to April 16, 2020. Underlying causes of AMS on arrival to the emergency department (ED) were categorized as (1) neurological causes (stroke, seizure, encephalitis); (2) metabolic encephalopathy; (3) indeterminant. Multivariable analysis was used to assess independent predictors. RESULTS: Overall, 166 patients presented to the ED with AMS. Metabolic encephalopathy was diagnosed as the cause in 154 (92.8%), with 118 (71.1%) categorized as multifactorial ME and 36 (21.7%) with single-cause ME. Hypoxia 103 (62.0%) and renal failure 75 (45.2%) were the most common underlying mechanisms. Neurological causes of AMS occurred in a total 20 patients (12%) and as the sole factor in 5 (3.0%); 10 (6.0%) cases were seizure related and 10 (6.0%) were cerebrovascular events. Of the 7 patients with indeterminant causes, only 1 was suspicious for encephalitis (0.6%). Age, pre-existing dementia and cerebrovascular disease, and impaired renal function were independent predictors of AMS. CONCLUSION: In patients with COVID-19, AMS on presentation to the ED is most frequently caused by metabolic encephalopathy (delirium). Seizures and cerebrovascular events contribute to a lesser degree; encephalitis appears rare. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00415-021-10623-5.