= INTRAVENTRICULAR NEUROBLASTOMA

= benign primary neoplasm of lateral + 3^rd ventricles

Incidence: unknown; tumor frequently mistaken for intraventricular oligodendroglioma

Age: 20–40 years

Histo: uniform round cells with central round nucleus + fine chromatin stippling ± perivascular pseudorosettes, focal microcalcifications (closely resembling oligodendroglioma but with neuronal differentiation into synapselike junctions)

Location: body ± frontal horn of lateral ventricle, may extend into 3^rd ventricle

• entirely intraventricular well-circumscribed tumor, coarsely calcified (69%), containing cystic spaces (85%)
• mild to moderate contrast enhancement
• attachment to septum pellucidum CHARACTERISTIC
• ± hemorrhage into tumor / ventricle
• hydrocephalus
• peritumoral edema extremely uncommon

MR:

• isointense relative to cortical gray matter on T1WI + T2WI with heterogeneous areas due to calcifications, cystic spaces, vascular flow voids (62%)

Rx: complete surgical resection

DDx:

1. Intraventricular oligodendroglioma (no hemorrhage)
2. Astrocytoma (peritumoral edema in 20%)
3. Meningioma (almost exclusively in trigone, >30 years of age)
4. Ependymoma (in + around 4^th ventricle / trigone, in childhood)
5. Subependymoma (in + around 4^th ventricle, young adult)
6. Choroid plexus papilloma (body + posterior horn of lateral ventricle, intense enhancement, younger patient)
7. Colloid cyst (anterior 3^rd ventricle / foramen of Monro, calcifications uncommon)
8. Craniopharyngioma (extraventricular origin)
9. Teratoma + dermoid cyst (fat attenuation)