Cephalhydrohematocele due to catheter valve disconnection following ventriculoperitoneal shunting.

A 5-year-old boy with a right-sided ventriculoperitoneal shunt presented with a 3-month history of progressively enlarging subperiosteal fluid collection in the scalp, which started in the right parietal region and had spread and extended across the midline to occupy both parietal regions. There were no changes in symptoms or signs from those observed 3 months previously. A CT scan confirmed the collection of fluid under the scalp over both parietal regions. The peritoneal catheter was found to be disconnected from the distal end of the functioning valve, which drained cerebrospinal fluid into the subperiosteal space. Distention of the parietal subperiosteal space led to stretching and tearing of the emissary veins. This resulted in the formation of a hydrohematocele. The spread of fluid to the opposite parietal region may be due to a disorganized and loose attachment of the periosteum to the widely separated sagittal suture.