ADEM in COVID-19
Neurological symptoms were the main presentation of COVID-19, which did not correlate with the severity of respiratory symptoms. The high incidence of ADEM with hemorrhage is striking. Brain inflammation is likely caused by an immune response to the disease rather than neurotropism. CSF analysis was not indicative of an infectious process, neurological impairment was not present in the acute phase of the infection, and neuroimaging findings were not typical of classical toxic and metabolic disorders. The finding of bilateral periventricular relatively asymmetrical lesions allied with deep white matter involvement, that may also be present in cortical gray-white matter junction, thalami, basal ganglia, cerebellum, and brainstem suggests an acute demyelination process. Additionally, hemorrhagic white matter lesions, clusters of macrophages related to axonal injury and ADEM-like appearance were also found in subcortical white matter. Causes
Since the discovery of the anti-MOG specificity against multiple sclerosis diagnosis it is considered that ADEM is one of the possible clinical causes of anti-MOG associated encephalomyelitisAbout how the anti-MOG antibodies appear in the patients serum there are several theories:

A preceding antigenic challenge can be identified in approximately two-thirds of people. Some viral infections thought to induce ADEM include influenza virus, dengue, enterovirus, measles, mumps, rubella, varicella zoster, Epstein–Barr virus, cytomegalovirus, herpes simplex virus, hepatitis A, coxsackievirus and COVID-19. Bacterial infections include Mycoplasma pneumoniae, Borrelia burgdorferi, Leptospira, and beta-hemolytic Streptococci.
ADEM shows seasonal variation with higher incidence in winter and spring months which may coincide with higher viral infections during these months. The mortality rate may be as high as 5%; however, full recovery is seen in 50 to 75% of cases with increase in survival rates up to 70 to 90% with figures including minor residual disability as well. The average time to recover from ADEM flare-ups is one to six months. ADEM produces multiple inflammatory lesions in the brain and spinal cord, particularly in the white matter. Usually these are found in the subcortical and central white matter and cortical gray-white junction of both cerebral hemispheres, cerebellum, brainstem, and spinal cord, but periventricular white matter and gray matter of the cortex, thalami and basal ganglia may also be involved. When a person has more than one demyelinating episode of ADEM, the disease is then called recurrent disseminated encephalomyelitis or multiphasic disseminated encephalomyelitis (MDEM). Also, a fulminant course in adults has been described. Signs and symptoms
ADEM has an abrupt onset and a monophasic course. Symptoms usually begin 1–3 weeks after infection. Major symptoms include fever, headache, nausea and vomiting, confusion, vision impairment, drowsiness, seizures and coma. Although initially the symptoms are usually mild, they worsen rapidly over the course of hours to days, with the average time to maximum severity being about four and a half days. Additional symptoms include hemiparesis, paraparesis, and cranial nerve palsies.