Shunted Hydrocephalus vs. Dandy Walker Cyst
Left picture: The diagnosis is a residual macrocephaly in an already shunted hydrocephalus. Right picture: In this schoolchild the macrocephaly is caused by a Dandy Walker cyst. The supratentorial ventriculomegaly has decreased to normal size following simple shunting. However, the Dandy Walker Cyst has continuously increased because the combined aqueductal stenosis or insufficiency hinders a sufficient outflow of CSF from the cyst of the IVth ventricle back into the supratentorial ventricles and from there in the shunt; on the other hand, the CSF cannot leave the Dandy Walker cyst because the foramina are occluded as part of the malformation. This increasing cyst led to a distinct occipital bossing and an elongated skull (dolichocephaly). Makrocephaly after shunt insertion is an important differential diagnosis of a macrocrania, mainly if the history of a former shunt treatment is unknown. Although the aim of shunting is a normalization of the head, it is not the case with all patients: Either, surgery has been performed too late, or a latent shunt dysfunction has occurred without overt clinical signs; both incidents can be avoided by an early referral or by regular follow-ups.
An infant and a schoolchild with a recognizable macrocephaly. Left picture: Macrocephaly in a 7-month-old boy in whom the well proportioned neurocranium is too large in comparison with the face. Right picture: In this schoolchild the neurocranium is too large, and there is a dolichocephaly with a distinct occipital bossing somewhat hidden by the hair. A scar is visible in the hair which is due to a ventriculoperitoneal shunt performed in infancy. The occipital bossing has increased remarkably during growth.