This patient presents for seizures. She was previously diagnosed with multiple myeloma in April 2009 and underwent a T11 hemilaminectomy for a pathological fracture. Neurological examination today reveals abnormal proprioceptive positioning, worst on the left and in the pelvic limbs.
PRE-CONTRAST BRAIN MRI STUDY A standard pre-contrast brain series is available for review. There is a small, rounded mass-like lesion (approximately 1cm in diameter) which is extraaxial in the region of the right frontal lobe of the brain that is mildly T1 hyperintense and T2 hypointense. There is marked associated T2 and FLAIR hyperintensity surrounding this mass rostrally and caudally, tracking through the regional white matter. The T2 and FLAIR hyperintensity can be followed rostrally towards the region of the right olfactory peduncle. A mass effect is seen in the region of the primary mass with mild leftward deviation of the falx cerebri and ventral compression of the right lateral ventricle.
POST-CONTRAST BRAIN MRI STUDY A transverse T1 weighted post-contrast sequence is available for review. Further imaging was not performed due to anesthetic complications. The previously described mass-like lesion of the right frontal lobe is strongly heterogeneously contrast enhancing with an associated dural tail sign extending circumferentially. A secondary smaller extraaxial mass is seen at the periphery of the left frontal lobe at the level of the rostral margin of the right sided mass. A third mass measuring approximately 1cm in diameter is present at the caudodorsal aspect of the right olfactory peduncle. This mass also has associated dural enhancement.
Multifocal strongly enhancing extraaxial masses within the left and right frontal lobes and the right olfactory peduncle with associated perilesional edema. Multiple meningioma is most likely, although given the patient’s history, metastatic plasma cell tumor cannot be completely ruled out.
All samples submitted are histologically consistent with meningioma. In most of the sections whorls of neoplastic cells frequently surround circular mineralized areas (psammomatous subtype). In other regions the mineralized bodies are less frequent and the mass is more consistent with the transitional subtype. The psammomatous subtype is associated with small islands of mineralization on histopathology.
Meningiomas arise from meningoepithelial cells. Meningiomas are common in dolicocephalic dogs such as Golden Retrievers and German Shepherds. Multiple meningiomas in dogs have been reported in three clinical cases, as well as one case in a pathologic series. Cats frequently have multiple meningiomas compared to dogs, occurring in up to 17% of cases. These multiple masses may be multicentric disease or may represent metastasis from a single lesion.
Imaging features of meningioma include broad based, extra-axial, strongly contrast enhancing masses. Additional findings can include hyperostosis and a dural tail (60%). Edema is common, and peritumoral cysts can be found in approximately 30% of cases. Interestingly, hyperostosis has only been reported in one dog, whereas it is more common in cats. Hyperostosis was not seen in this case.
The dural tail is not specific for meningiomas as it may be caused by other extra-axial lesions. It is unclear whether this is secondary to tumor extension along the dura or inflammation or thickening of the adjacent dura.
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