COVID-19-associated acute necrotising encephalopathy successfully treated with steroids and polyvalent immunoglobulin with unusual IgG targeting the cerebral fibre network.

A recent case report described the radiological features of a suspected COVID-19 necrotising haemorrhagic encephalopathy.1 We present here a description of clinical, biological, radiological and immunological features of a COVID-19 patient case, evocative of virus-associated acute necrotising encephalopathy (ANE) possibly mediated by antibodies. Patient’s representative consent has been obtained in agreement with the journal’s policy. A 51-year-old man without personal or family history of neurological disease was hospitalised after 10 days of fever and cough. COVID-19 was diagnosed by reverse-transcriptase PCR on nasal swab and bilateral ground-glass opacities on thoracic CT scan. At day 12, he was admitted in intensive care unit (ICU) for non-invasive ventilation. The result of the neurological examination was normal. At day 21, while the patient had been weaned off oxygen, he became unresponsive and rapidly comatose (Glasgow Coma Scale 6: E1, V1, M4) with a disconjugated gaze. The patient was groaning and showing rhythmic movements of the right upper limb. An urgent brain MRI, including diffusion-weighted imaging (DWI) and MR angiogram, ruled out vertebrobasilar ischaemic stroke; gradient echo T2*-weighted images excluded haemorrhage and thrombus in the venous system. It revealed only subtle hyperintensities in bilateral thalami on FLAIR sequence (figure 1). Consciousness impairment required tracheal intubation. He was hyperthermic (39°C) without shock. Blood and cerebrospinal fluid (CSF) samples revealed thrombopenia and lymphopenia, mild inflammatory response (C reactive protein, ferritin and fibrinogen), CSF albumin-cytological dissociation with increased CSF IgG antibodies (91.9 mg/L, normal 10–30 mg/L) and altered blood–brain barrier integrity (CSF/serum albumin index=17.3, normal <6.5) (online supplementary material). An electroencephalogram revealed symmetrical background activity of low-voltage delta waves without spatial organisation, triphasic waves or paroxysmal activity. He showed unresponsive coma (Glasgow Coma Scale=3), pyramidal syndrome, right-sided sixth nerve palsy and no corneal reflex. A second brain contrast-enhanced MRI at day 22 revealed progressing lesions with diffuse hyperintense …