Dural-Based Posterior Fossa Cavernous Malformation: A Case Report

Introduction: Dural-based cavernous malformations presenting in the posterior fossa are a rare medical entity. Cerebral cavernous malformations (CMs) are benign vascular lesions that have a prevalence of 0.4 to 0.6% in the general population. Dural-base CMs are far less common, with most cases being reported in the middle cranial fossa. We describe a case of a patient with an indolently growing posterior fossa lesion later found to be a dural-based CM.

Methods: Patient clinical history, imaging, operative findings, and histologic analysis were obtained via chart review. Patient consent was obtained per standard protocol.

Results: The patient is a 40-year old male with a past medical history notable for migraines since childhood associated with visual disturbance, right-sided numbness and tingling, and gait instability. He was referred to neurology for migraine workup and had a magnetic resonance imaging (MRI) of his brain that demonstrated a 1.9 cm T1 contrast-enhancing, T2 hyperintense lobulated extra-axial lesion. The patient’s symptoms were felt to be unrelated and surveillance was recommended. Three years later, repeat MRI demonstrated growth of the lesion, now 2.1 cm. Given the increase in size, the patient opted to proceed with surgical resection. A standard suboccipital craniectomy was performed, with dural opening extending to involve the lesion in its entirety. During resection, an arachnoid plane was maintained around the lesion noting no intraparenchymal extension. There were no intra- or postoperative complications and the patient was discharged home on postoperative day 2. Grossly, the lesion was a well-circumscribed 2.1 × 2.0 × 1.8 cm tan-red ovoid mass composed of fibromembranous tissue. H&E staining demonstrated closely packed blood vessels with hyalinized and fibrotic walls. The tumor was negative for epithelial membrane antigen (EMA). SSTR2, common in meningiomas, only stained occasionally in inflammatory cells. Smooth muscle actin (SMA) staining, typically negative in meningiomas, was positive and highlighted vessel walls. Formal histologic diagnosis was consistent with cavernous malformation.

Conclusion: Posterior fossa dural-based cavernous malformations are rare and can be radiographically difficult to distinguish from meningiomas. Both can be T1 contrast enhancing, T2 mixed to hyperintense, and hyperdense on CT. CM’s have a rate of hemorrhage of 2 to 3% per year in lesions that have not previously bled. Thus, distinguishing these two entities is important in patient counseling and management. Although rare, dural-based CM should be kept in the differential diagnosis for certain patients. Further investigation is needed to determine a method of pre-operative differentiation of these lesions.

Publication History

Article published online:
07 February 2025