The dural lucent line: characteristic sign of hyperostosing meningioma en plaque.

Hyperostosis of the skull associated with en plaque form of meningioma may present a diagnostic challenge, since the intracranial part of the tumor is not visualized by skull radiography, computed tomography (CT), or other neuroradiologic methods. The authors report four cases of hyperostosing meningioma en plaque demonstrating a characteristic feature: a subdural layer of ossification along the hyperostotic bone with a dural lucent interface. Polytomography or high-resolution CT at bone window settings is necessary to identify the dural lucent line. The absence of this sign does not exclude meningioma en plaque.