To describe the neurological disorders associated with COVID-19 in Singapore.

Various neurological disorders have been reported in COVID-19 patients. Postulated mechanisms include hypercoagulopathy, dysimmunity, inflammation and direct viral invasion. The incidence and relationship to SARS-CoV-2, considering the confounding effect of a surge in COVID-19 cases on healthcare systems, are unclear.

This was a prospective, nation-wide, multi-centre, cohort study of patients with microbiologically-confirmed COVID-19 referred for any neurological complaints within 3 months of infection. Neurological diagnoses and relationship to COVID-19 were made by consensus guided by contemporaneous published case definitions.

Between March-July 2020, 47,572 patients [median age 34 (1-102) years, 98% males] were diagnosed with COVID-19 in Singapore. Of 90 patients referred for neurological disorders, 39 [median age 41 (27-73) years, 97% males] were deemed related to COVID-19 and categorised as: i) Central nervous system syndromes - 3 encephalitis, 1 acute disseminated encephalomyelitis; ii) Cerebrovascular disorders - 19 acute ischemic stroke/transient ischemic attack (AIS/TIA), 4 cerebral venous thrombosis (CVT) and 2 intracerebral haemorrhage; iii) Peripheral nervous system - 7 mono/polyneuropathy;  iv) Autonomic nervous system - 4 limited dysautonomia. Fifty-one other patients had pre/co-existent neurological conditions (headache, seizure, mononeuropathies and functional neurological disorders) unrelated to COVID-19. Encephalitis is delayed, occurring in critical COVID-19, while CVT and dysautonomia occurred relatively early and largely in mild infections. AIS/TIA was variable in onset; remarkably 63.2% had asymptomatic COVID-19. CVT was more frequent than expected and occurred in patients with mild/asymptomatic COVID-19. The pathophysiology of COVID-19 neurology appeared to be dysimmunity and/or prothrombotic tendency. There were no neurological complications in all 81 paediatric COVID-19 cases.

COVID-19 neurology has a wide spectrum of dysimmune-thrombotic disorders. The relatively few cases recorded was probably because our outbreak affected mainly healthy young men with mild/asymptomatic COVID-19 and the pandemic did not unduly affect the Singapore healthcare system.