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Schwannoma are benign, slowly growing nerve sheath tumors. They can arise from any peripheral nerve containing Schwann cells including distal portions of cranial nerves. Intracranial schwannomas arising from a subfrontal lesion are very rare. We report a case of subfrontal schwannoma in a 38-year-old woman who presented with seizures in February 2003. MRI features resembled an olfactory groove meningioma. The left carotid angiography revealed that the tumor was supplied from the anterior ethomoidal artery, but no remarkable tumor stain was detected. Bifrontal craniotomy with total excision of the tumor revealed a tumor in the left subfrontal lesion. The tumor was attached to the falx, the left frontal lobe, and the skull base, but those structures were not invaded. Unfortunately, we could not detect the left olfactory nerve. Subsequent histological examination proved that this tumor was schwannoma. A review of the literature found 27 cases including this case previously described. Arguments are raised that schwannomas in a subfrontal lesion are comparable to or even occur as intracranial schwannomas with frontal localization. Subfrontal schwannomas are very rare. For this reason they have not been diagnosed preoperatively. Further cases of subfrontal schwannoma are necessary to solve the enigma of the origin of this tumor.

In order to achieve complete irrigation, reduce air in the hematoma cavity, and obtain rapid reduction of the cavity without drainage, we use burr-hole evacuation of the hematoma followed by irrigation using physiologic saline solution and replacement of the hematoma with carbon dioxide (CO2) gas. We have treated 19 cases between the ages of 41 and 84. With the exception of one case with dementia of 5 years' duration, all cases were asymptomatic postoperatively. Computed tomography (CT) scans obtained immediately postoperatively showed the gas to fill the hematoma cavity, but on the following day, the gas and the hematoma cavity had nearly disappeared. There was no surgical mortality nor morbidity and there were no side effects of the CO2 gas. Recurrence was found in one case (5.3%). By filling the hematoma cavity with CO2, disappearance of the cavity is rapid and drainage is not needed. Moreover, this technique implies no restrictions on postoperative motility, and is thus suitable for elderly patients.

We tried to examine the growth pattern of meningeal gliomatosis (MG) by using an experimental MG model. C6 rat glioma cells (3 X 10(5)/0.1 ml) were injected percutaneously into the cisterna magna of rats. Seven days after inoculation, the brains and spinal cords were removed and processed for morphological observation. Light microscopic findings showed that numerous tumor cells had invaded the spinal cord parenchyma directly and/or via the Virchow-Robin spaces. In contrast, a small amount of tumor cells had spread horizontally on the surface of the spinal cord. By transmission electron microscopy, discontinuity of the basal lamina (of the marginal glia) was found, and some tumor cells were found to have protruded their processes into the spinal cord parenchyma. A basal lamina-like granular material was observed in the vicinity of these areas, indicating the breakdown of the basal lamina. Scanning electron microscopic findings further supported the speculation concerning the penetration of the pia mater by tumor cells through the small pores which had blunt margins. From these ultrastructural observations, we speculated that some chemical membranolytic factors might play an important role in MG.