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Two cases of clear cell ependymoma (CCE) of the fourth ventricle are reported in a 49-year-old woman with dysphagia and a 59-year-old woman with dizziness and gait disturbance. CCE is a relatively new variant of ependymoma added to the WHO classification of tumors in 1993. Tumor cells display an oligodendroglioma-like appearance with a clear perinuclear halo. Most infratentorial CCE tumors are located in the cerebellum. There are only three cases, including the present two cases, that have been reported to affect the fourth ventricle.

The authors describe the case of a 69-year-old man with an intracerebral hemorrhage due to rupture of a nontraumatic aneurysm of the middle meningeal artery (MMA). The ipsilateral posterior cerebral artery (PCA) was occluded, and dural anastomoses developed as the main collateral pathway between the MMA and the cortical branch of the PCA, on which the aneurysm was located. It is considered that increased hemodynamic stress to the collateral pathway contributed to the formation of the aneurysm.

A neoplastic cerebral aneurysm from lung cancer is an extremely rare occurrence despite its high metastatic potential to the brain. We report a neoplastic cerebral aneurysm from small-cell lung carcinoma that caused an intracerebral hematoma. A 63-year-old man underwent an urgent craniotomy for a massive intracerebral hematoma. After evacuation of the hematoma, an anomalous artery was found on the wall and a biopsy was done. The histological examination revealed that the artery was filled with neoplastic cells, and a part of the vessel wall was distended, forming an aneurysm. The histological feature of the tumor cells was consistent with small-cell lung carcinoma, which was disclosed in the left hilus.