The veins of the medulla oblongata: MRI cross-sectional anatomy.

Magnetic resonance imaging (MRI) has progressively become the major or even the only imaging procedure for displaying the vascular relationships of the brainstem in the context of infra-tentorial lesions. In order to assess the MR sectional anatomy of the bulbar vv. 40 normal patients were examined in the MR axial, frontal and sagittal planes after gadolinium i.v. injection. The bulbar venous networks were inconstantly visualised: anterior vv. (16%). posterior (3%), lateral (8%). The vein of the lateral recess of the fourth ventricle was constant in the three planes; the inferior petrosal sinus could be seen in 82% of cases. Their relation with the posterior fossa structures are emphasised and discussed.