Ring enhanced aneurysm due to vasa vasorum of aneurysm wall mimicking a metastatic brain tumor.

Background: A spherical intracranial mass can be occasionally misdiagnosed due to the lack of typical radiographic features. Completely thrombosed intracranial aneurysms (CTIA) are uncommon, but a possible differential diagnosis must be considered to guarantee the best surgical approach for these lesions.

Case Description: Here, we report an extremely rare case of a right frontal mass mimicking a brain tumor, in which the surgery unveiled a CTIA of the right middle cerebral artery (MCA). A 56-year-old woman presented with right hemiparesis and mild headache. Magnetic resonance imaging (MRI) revealed a right frontal mass with peripheral edema. The lesion enhanced on initial and follow-up MRI of the brain. Subsequent vascular studies and metastatic workup were negative. A temporal craniotomy with neuronavigation (Brain Lab AG, Germany) was performed and an intraoperative diagnosis of a thrombosed aneurysm along the branch of the MCA was established. The aneurysm was successfully trapped and resected. The patient did not exhibit any postoperative neurological deficits.

Conclusion: This is the rare report of a ring enhanced completely thrombosed aneurysm due to vasa vasorum which is misdiagnosed as metastatic brain tumor. In case of an intracranial ring enhanced mass with signs of intralesional hemorrhage and peripheral edema, CTIA should be considered as a possible differential diagnosis.