Pilocytic astrocytoma of the velum interpositum.

A 72-year-old male presented with a pilocytic astrocytoma in the velum interpositum manifesting as a 5-day history of dizziness attacks and unstable gait. Computed tomography and T1-weighted magnetic resonance imaging with gadolinium enhancement demonstrated a small, homogeneously enhanced mass in the velum interpositum. The tumor was removed subtotally, and the structure of the splenium was intact. The histological diagnosis was pilocytic astrocytoma. The MIB-1 growth fraction was 5%. The tumor may have originated from the splenium or the thalamus. The aggressive histology indicates the need for close neuroimaging follow-up.