Chiari 1 anatomy following ventriculoperitoneal shunting:Posterior fossa volumetric evaluation with MRI

Abstract

Cephalocranial disproportion has been said to be responsible for Chiari 1 malformation following ventriculo-peritoneal shunt. We aimed to evaluate if the volumetric characteristics of Chiari 1 following a ventriculo-peritoneal shunt was due to a general volumetric reduction or restricted to the Posterior fossa. Our results show that the posterior fossa volume, cisternal, clival length and posterior cranial fossa volume ratio were reduced in the shunted group compared to the controls. p<0.05. Cerebellar and Supratentorial volumes were similar between both groups. Craniocaudal extent, inferior and superior tonsilar herniations were more in the shunted group than controls. p<0.05 . The frontal occipital horn ratio in both groups was within normal range. Chiari 1 anatomy following a ventriculo-peritoneal shunt could develop in children and we propose a ‘Posterior cranial fossa disproportion’ rather than a ‘Cephalocranial disproportion’.