A female infant with macrocephaly (head circumference >95th%), hydrocephalus, and Dandy-Walker syndrome, who developed horizontal head movements of the 'no-no' type at 1 year of age, is reported from Federal University of Minas Gerais, and other centers in Brazil. CT scan on day 1 of life showed a posterior fossa cyst, hypoplasia of the cerebellar vermis, elevation of the occipital lobe, and an increase in size of the posterior fossa, findings compatible with the Dandy-Walker syndrome. With progressive enlargement of the head, a VP shunt was inserted on day 9. She developed normally in the first year and walked at 14 months. The head circumference was at the 5th percentile, and an MRI confirmed the cerebellar vermis hypoplasia and cyst, without signs of compression, enlargement or displacement of third or fourth ventricles or brainstem. Withdrawal of fluid from the fourth ventricle resulted in no change of the doll's head movements. At 3 year follow-up, head movements persisted, but the neurological examination and milestones of development were otherwise normal. Movements were worse when walking or with stress and they disappeared in sleep. 
COMMENT. The case-report suggests that bobble-head doll syndrome (BHDS) may occur with cerebellar malformation, and hydrocephalus with third ventricle dilatation is not an essential causative factor. Movements are usually up and down ('yes-yes' type), and the 'no-no (side-to-side) movements seen in this case are rarely reported. The most common cause is a tumor or cyst and dilatation of the third ventricle, and movements often cease after ventricular drainage. Other causes include suprasellar arachnoid cyst, and aqueductal stenosis with hydrocephalus. Age of onset varies from 2 months to 13 years. The mechanisms suggested for BHDS include pressure on the medial aspect of the dorsomedial thalamic nucleus, intermittent obstruction of the formaen of Monro, or compression of the red nucleus. Malformation of the cerebellum, especially involving the vermis, may also be involved.