Head shaking by visually impaired children: a voluntary neurovisual adaptation which can be confused with spasmus nutans.

Rapid, horizontal, pendular head oscillations were observed in 18 visually impaired children with nystagmus during intense visual fixation, and the characteristics of this behaviour were analysed. Head tilting and eye deviations also occurred in 14 of the children. Their symptoms and signs resembled spasmus nutans. Head shaking appeared to be a voluntary, learned, neurovisual adaptation to improve visual acuity. Accurate simultaneous recordings of eye and head movements are required to understand the pathophysiological significance of these head oscillations.