(1) The brainstem consists of the midbrain, pons and medulla, structures located deep in the back of the brain.(2) The twentieth century opened with knowledge that the brainstem (pons and medulla) generates regular breathing.(3) Nearly all cases of PML involve the cerebral white matter, but it may also involve white matter of cerebellum, brainstem and spinal cord.(4) Some afferent fibres from the epiglottis, palate and pharynx also reach the brainstem via the vagus nerve.(5) Following replication, the virus enters axons and is transported in a retrograde manner to involve the spinal cord and eventually the brainstem , cerebellum, and cortex.
