ICANS has been associated with acute white matter (WM) microvascular and macrovascular injury on imaging, including hemorrhagic and nonhemorrhagic encephalitis and strokes. Incidentally, NfL elevations are also associated with WM lesions and neuroinflammatory and vascular insults such as stroke, encephalitis, and lesion burden in multiple sclerosis. Together this suggests possible subclinical WM injury through microvascular injury via an as of yet uncharacterized pathway. This evidence concerns the gene NEFL and viral encephalitis.