BACKGROUND: Spasmus nutans is defined as asymmetric nystagmus with associated head nodding in childhood. It is not clear whether head nodding is a compensatory mechanism to control the nystagmus or an involuntary movement of pathologic origin. METHODS: The authors analyzed the relation between head and eye movements by simultaneous eye and head movement recordings of 35 patients with spasmus nutans. RESULTS: In 21 of these patients, the fine, fast, dissociated nystagmus changed during head nodding to larger and slower symmetric eye movements with both eyes oscillating at the same amplitude in phase and 180 degrees out of phase to the head movements, corresponding to a normal compensatory vestibulo-ocular reflex. CONCLUSION: These findings indicate that head nodding is compensatory in spasmus nutans.
BACKGROUND: Spasmus nutans is defined as asymmetric nystagmus with associated head nodding in childhood. It is not clear whether head nodding is a compensatory mechanism to control the nystagmus or an involuntary movement of pathologic origin. METHODS: The authors analyzed the relation between head and eye movements by simultaneous eye and head movement recordings of 35 patients with spasmus nutans. RESULTS: In 21 of these patients, the fine, fast, dissociated nystagmus changed during head nodding to larger and slower symmetric eye movements with both eyes oscillating at the same amplitude in phase and 180 degrees out of phase to the head movements, corresponding to a normal compensatory vestibulo-ocular reflex. CONCLUSION: These findings indicate that head nodding is compensatory in spasmus nutans.