Dural-based cavernoma presenting as a large extra-axial cyst: a rare case report and focused literature review

BACKGROUND: Cerebral cavernous malformations (CCMs) are benign vascular lesions most commonly found within the brain parenchyma. Extra-axial and dural-based cavernomas are exceedingly rare, and cystic variants are even less frequently described. Their radiological appearance may mimic more common extra-axial lesions, posing a potential diagnostic challenge. We report a unique case of a dural-based cavernoma presenting as a giant extra-axial cyst with recurrent haemorrhage rhage, and we review the relevant literature. CASE DESCRIPTION: A 30-year-old woman was followed for a decade for a large left fronto-temporal extra-axial cyst, initially discovered incidentally. Serial MRI scans demonstrated a slowly enlarging cyst with high T2/FLAIR signal, low-intermediate T1 signal, and mild peripheral enhancement. Later follow-up imaging revealed an interval haemorrhage rhage within the cyst. She subsequently presented with a transient episode of dysphasia and right-hand numbness. CT confirmed acute bleeding into and around the cyst with mild mass effect. She soon underwent an elective fronto-temporal craniotomy. Intraoperatively, a thick-walled cyst with multiple septations was evacuated, and a dural-based vascular lesion near the temporal base was excised. Histopathology confirmed a cavernous malformation with haemorrhage rhage, hemosiderin deposition, and chronic inflammation. Postoperatively, she recovered rapidly without complications. CONCLUSION: This case illustrates a rare presentation of a dural-based cystic cavernoma mimicking an atypical extra-axial cyst. The absence of classic CCM imaging features, together with cystic morphology and mild wall enhancement, contributed to the diagnostic complexity. Dural-based cavernomas should be included in the differential diagnosis of giant extra-axial cysts that do not follow CSF intensity on all MRI sequences.