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.
