Results (1) 31 cases showed clivus involvement, 6 of which had mass in prepontile cistern. (2) Involvement via hypoglossal nerve canal was seen in 3 cases, presenting enlarged nerve canal in 2.

• (2)经舌下神经管侵犯3例，左侧2例有舌下神经管扩大，右侧1例不扩大，3例颅内外肿块均经舌下神经管相连形成“哑铃”状。