# Beyond Aqueductal Stenosis: A Case of an Atypical Teratoid/Rhabdoid Tumor Presenting With Neonatal Hydrocephalus

## TL;DR

A rare brain tumor in a newborn was initially mistaken for a common condition, highlighting the challenges in diagnosing atypical teratoid/rhabdoid tumors.

## Contribution

The paper presents a unique neonatal case of ATRT misdiagnosed as aqueductal stenosis, emphasizing diagnostic difficulties in infants.

## Key findings

- Neonatal ATRT can mimic aqueductal stenosis on prenatal imaging.
- Postnatal MRI revealed a hemorrhagic mass in the tectum, later confirmed as ATRT.
- Loss of SMARCB1 (INI1) expression was identified as a key diagnostic marker.

## Abstract

An atypical teratoid/rhabdoid tumor (ATRT) is a rare and highly aggressive embryonal tumor in the central nervous system, with the highest incidence in infants. Neonatal cases frequently experience delayed diagnosis due to nonspecific symptoms, with imaging findings that may mimic more prevalent congenital anomalies such as aqueductal stenosis. We report a case of a full-term male neonate with prenatal findings of severe lateral and third ventriculomegaly, initially misdiagnosed to be due to an obstructive etiology due to hemorrhage in the fourth ventricle/aqueduct. Later, on a postnatal MRI, a non-enhancing hemorrhagic mass was suspected to be arising from the tectum, which on histopathology was confirmed to be an ATRT with loss of SMARCB1 (INI1) expression.