[Meningioma of the optic canal. Diagnostic aspects apropos of 3 surgically treated cases].

Three cases of meningiomas originated in the optic nerve sheath in its intra-canalicular portion, have been operated on in Reims since we dispose of the TDM; it gave us the opportunity to re-define the way how to explore an area always difficult to investigate; indeed it has been impossible for a long time to clearly isolate meningiomas in the optic canal through the classical neuro-radiologic technics. The anatomic study confirms that the optic canal orientation is fixed, constantly inclined downward and forward with an angle of minus forty degrees with regard to the horizontal line; our work establishes that it is possible to apply it to the CT scan; in this incidence, TDM perfectly allows to visualize the optic canal and the optic nerve, from the anterior clinoid process to the posterior orbital pole. This incidence seems us to be interesting, in addition to classical neuro-ophthalmic planes, for early diagnosis or supervision of tumors of the optic canal.