One-and-a-Half Syndrome, Facial Palsy, and Nystagmus Due to Dorsal Pontine Demyelination

This is a 16-yo-girl with oscillopsia and double vision. Exam showed inability to look to the left with either eye due to left nuclear 6th. There was also a left INO (horizontal gaze palsy + INO = one-and-a-half syndrome) from left MLF involvement and left lower motor neuron facial palsy due to fascicular 7th nerve involvement. One-and-a-half syndrome + facial (7th) palsy = "eight-and-a-half syndrome". There was also upbeat-torsional nystagmus, presumably due to involvement of the vertical semicircular canal pathways (mainly involving the anterior pathways given downward slow and upward fast phase). The anterior canal pathways travel through the superior conjunctivum, ventral tegmental tract, and MLF, whereas the posterior canal pathways travel through the MLF only.