Trapped fourth ventricle

1-Patient suffering from aqueductal stenosis which is treated by application of a shunt tube.

2-After that, outlet foramina will be also obstructed for some reasons.

3-At that time, the lateral and third ventricle will be drained by shunt tube, while the fourth ventricle is enlarged because choroid plexus inside it still secreting CSF while outlet foramina is obstructed.

4-D.D. from posterior fossa tumors.

Trapped fourth ventricle