Differences on intraoperative ultrasonography between meningioma and neurilemmoma.

We examined the differences on intraoperative ultrasonography between 17 cases of meningioma and 29 of neurilemmoma, the common intradural extramedullary tumors. In meningiomas, cysts were rarely seen (in 12.5%, P < 0.01%) and echogenicity was high (in 82.3%, P < 0.01%). In neurilemmoma, many cysts were seen (72.5%) and low echoes tended to be more common (72.4%, P < 0.01%). In the neurilemmomas with high or isoechogenicity, Antoni A types, histologically rich in collagen fibres, predominated.