Although abducens nerve palsy is a relatively common disease, the abducens nerve has been almost impossible to identify, because it is one of the finest cranial nerves and runs three-dimensionally in the prepontine cistern. Three-dimensional constructive interference in steady state (3D-CISS) is helpful in visualizing fine structural elements in the central nervous system because of its higher spatial resolution and fewer artifacts from cerebrospinal fluid. In this study, we successfully visualized the abducens nerve using 3D-CISS. The procedures were as follows : first, Dorello's canal and the ponto-medullary sulcus were identified as visible, landmarks, and then the abducens nerve was followed to the root exit zone ; second, the gray scale of the original image was inverted to clearly visualize the cisternal course of the nerve and the neighboring small vessels ; and, finally, the entire cisternal course of the nerve was visualized in the same images in both oblique axial and oblique sagittal planes by a multi-planar reconstruction method. This reliable technique can be performed for the diagnosis of abducens nerve palsy.
