Pilocytic Astrocytoma Presenting with Spontaneous Cerebellar Hemorrhage: A Case Report.

Hemorrhagic pilocytic astrocytomas (PAs) are rare, accounting for 1.1%-8.0% of all PA cases. They are reported to occur more frequently in older populations, with a male predominance. In this study, we report a case of a 14-year-old boy who presented with a headache, vertigo, and diplopia. As per his brain computed tomography scan, a small hematoma was observed in the left inferior cerebellar peduncle. Follow-up magnetic resonance imaging (MRI) revealed repeated minor bleeding from the lesion and mild expansion, with no neurological deficits. Four years later, the patient developed nausea, vomiting, and left abducens palsy. MRI revealed a mulberry-shaped mass surrounded by a hypointense rim, suggesting a cavernous angioma. The lesion was surgically resected via midline occipital craniotomy with the opening of the cerebellomedullary fissure. Histopathological examination of the lesion revealed PA. Next-generation sequencing analyses revealed that PAs harbored mutations in the ARID1A, ATM, and POLE genes but not in the BRAF gene. To the best of our knowledge, there are yet no reported studies on these mutations in PAs to date. Thus, PA should be considered in the differential diagnosis of cerebellar hemorrhage, especially in young adults and children．.