Dissociated vertical-torsional nystagmus in vestibular nucleus lesion

Dissociated vertical-torsional nystagmus is a unique form of nystagmus characterized by conjugate torsional but disparate vertical components. It has been mainly reported in internuclear ophthalmoplegia or medial medullary lesion involving the medial longitudinal fasciculus (MLF). The patterns of the nystagmus may be explained by a disruption of vestibulo-ocular reflex pathways from vertical semicircular canal or utriculo-ocular reflex within the MLF, but it is debatable. We described a dissociated upbeat-torsional nystagmus in a patient with vestibular nucleus infarction without involvement of MLF.