Pilocytic Astrocytoma Causing Brainstem Compression in Pregnancy: Case Report with Literature Review

<b>Background:</b> Primary central nervous system tumours in pregnancy are exceptionally rare, with posterior fossa lesions presenting particular diagnostic and management challenges due to their confined anatomical location and proximity to critical neurovascular structures. Pilocytic astrocytoma (PA), typically a paediatric tumour, is uncommon in adults and exceedingly rare in pregnant patients. The physiological changes in pregnancy can obscure tumour-related symptoms, contributing to diagnostic delay and increased maternal-fetal risk. <b>Methods:</b> We report the case of a 24-year-old pregnant woman at 23 weeks and 5 days' gestation who presented with progressive neurological deterioration secondary to a cystic mass in the right cerebellar hemisphere. MRI revealed significant brainstem compression and triventricular hydrocephalus. <b>Results:</b> A multidisciplinary team performed an urgent retrosigmoid craniotomy with gross total tumour resection under general anaesthesia and continuous intraoperative fetal monitoring. Histopathology confirmed PA (CNS WHO Grade I). Postoperative recovery was uneventful, and both maternal and fetal outcomes were favourable. <b>Conclusions:</b> This case highlights the importance of early neuroimaging, multidisciplinary coordination, and timely surgical intervention in managing posterior fossa tumours during pregnancy. Although PAs are considered low-grade gliomas, their behaviour in pregnancy can be unpredictable. With careful perioperative planning, neurosurgical treatment can be safely undertaken during gestation, offering optimal outcomes for both mother and fetus.