Downbeat nystagmus indicates cerebellar or brain-stem lesions in vitamin B12 deficiency.
Two cases of vitamin B12 deficiency caused by gastric atrophy are described. Together with the neuropsychiatric features usually associated with this condition, a downbeat nystagmus syndrome was observed. It is concluded that vitamin B12 deficiency may also result in lesions to those cerebellar or brain-stem structures that are generally assumed to cause downbeat nystagmus.
D000368:Aged; D000752:Anemia, Pernicious / Q000150:complications*; D001927:Brain Diseases / Q000209:etiology; D001933:Brain Stem; D002526:Cerebellar Diseases / Q000209:etiology*; D005133:Eye Movements; D005260:Female; D006801:Humans; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000209:etiology*; D012021:Reflex, Abnormal / Q000209:etiology; D014722:Vestibule, Labyrinth / Q000503:physiopathology