Imaging Features of Pilocytic Astrocytoma in Cerebral Ventricles.

PURPOSE: Our aim was to identify imaging characteristics of pilocytic astrocytomas (PAs) in the cerebral ventricles to help radiologists distinguish PAs from other brain tumors preoperatively.

METHODS: Twelve postsurgery patients with a pathological PA diagnosis were included. Among them, 10 had submitted to surgery based on 3.0-T magnetic resonance imaging sequences and 7 because of computed tomography (CT) results. We analyzed their clinical and radiological records retrospectively.

RESULTS: The 12 patients (7 were male) had 13 lesions (11 with a single focus, 1 with multiple foci). Average age was 26.5 years (range, 6-49 years). Clinical symptoms included headache, dizziness, vomiting, and unstable gait. Tumor locations were the lateral ventricle (4), fourth ventricle (7), or both ventricles (1, but multifocal). One tumor had disseminated. PA diameters were 18.7-63.0 mm (mean ± standard deviation, 36.5 ± 12.4 mm). Nine had a round margin, and four had irregular margins. Two were cystic lesions. Eleven were mixed cystic and solid. CT showed the tumors as low-density masses. Two had calcifications. Their cystic portions showed low signal intensity (SI) on T1-weighted imaging (T1WI) and high SI on T2-weighted imaging (T2WI). The cystic walls and solid portions of the PAs showed slightly low SI on T1WI and slightly high SI on T2WI. After gadopentetate dimeglumine administration, the solid portion showed heterogeneous enhancement, whereas the cystic portion showed no enhancement.

CONCLUSIONS: Radiological features of intraventricular and extraventricular PAs were similar to typical ones, including enhanced nodules within cysts. Radiological findings can usually diagnose PAs correctly.