Acquired monocular nystagmus in monozygous twins.

Twins girls presented with monocular nystagmus, head-nodding, and tilting in early infancy. This disorder resolved without therapy or residual defect. This case represents the first documented report of spasmus nutans presenting with only monocular nystagmus in twins. The etiology of spasmus nutans and monocular nystagmus is discussed in light of recent clinical and experimental observations.