Third Ventricular Herniation

third ventricular herniation

This patient has severe obstructive hydrocephalus due to a tumour of the tectal plate (small arrows, click image for arrows). The patient was treated by third ventriculostomy. The immediate preoperative image on the left shows marked dilatation of the lateral and third ventricles. The corpus callosum is thinned and elevated. The fornices are depressed. The floor of the 3rd ventricle is plastered to the skull base, obliterating the suprasellar cistern. The infundibular and optic recesses are rounded (curved arrow). The pineal recess is also rounded, but the suprapineal recess appears deficient or ballooned. There is a cystic structure (large grey arrows) interposed between the tentorium cerebelli and the superior cerebellum, with marked mass effect. There is marked tonsillar herniation (black arrows), which is probably due to a combination of posterior fossa mass effect and a Chiari type I malformation.

Immediate postoperative imaging (right) shows reduction in the degree of hydrocephalus. The suprasellar cistern is no longer effaced, and the infundibular recess is sharper. The optic and pineal recesses remain rounded, although there is a definite improvement. The posterior fossa cystic structure has also reduced in size, consistent with a communication with the third ventricle – the cyst actually represents a herniation via the suprapineal recess. The tonsillar herniation has improved, as has effacement of CSF at the craniocervical junction.

Reference:
1. Osborn AG, Blaser SI, Salzman KL. Brain: Top 100 Diagnoses Amirsys 2004
2. Barkovich, AJ. Pediatric Neuroimaging 2nd edition. Raven Press 1995

Credit: Dr Laughlin Dawes, Dr Con Phatouros