Bobble-head doll syndrome: review of the pathophysiology and CSF dynamics.

The bobble-head doll syndrome is a rare movement disorder; fewer than 40 cases have been reported. It is usually associated with cystic abnormalities in the region of the anterior third ventricle. Various physiologic mechanisms have been proposed but none of them has been substantiated. We report a patient with this syndrome produced by a suprasellar arachnoid cyst. The CSF dynamics were investigated with CT cisternography. The phenomenon was apparently the result of intermittent obstruction at the foramina of Monro, a feature which has not previously been reported in this condition. The head movement served to partially relieve intraventricular obstruction, by both a posterior displacement of the cyst away from the foramina of Monro and a reduction in cyst size. This finding supports the concept that the bobble-head syndrome may be a "learned" behavior which lessens the symptomatology of hydrocephalus related to foramina of Monro obstruction.