Fig. 4.

Various proposed routes of neuro-invasion of SARS-CoV-2 after it entered into the host cells. 1- Migration of viral particles directly into the brain from the nasal passage via olfactory bulb, 2- hypoxia due to lung injury causes anaerobic respiration in the brain cells mitochondria leading to accumulation of acidic compounds that causes brain swelling, ischemia, and obstruction in cerebral blood flow, 3- cytokines and inflammatory markers released during the cytokine storm travel to the blood–brain barrier and increase its permeability, thus infiltrating into the brain, 4- virus infects the gastrointestinal tract and travels to the CNS via sympathetic afferent neurons in the enteric nervous system