Purpose: To investigate the anatomic relation between the optic nerve and the adjacent intracranial internal carotid artery (ICA) in patients with unexplained optic neuropathy.
Methods: Coronal magnetic resonance images (MRIs) of 20 patients with unexplained optic neuropathy and 20 age-matched controls were evaluated with digitizing software.
Results: The distance between the optic nerve and ICA was significantly less on the side ipsilateral to the atrophic optic nerve than either the study group's contralateral optic nerve-ICA distance (P<0.001) or the control group's optic nerve-ICA distance (P<0.001). The diameter of the atrophic optic nerves was significantly less than either the diameter of the study group's contralateral normal nerves (P=0.008) or the control group's nerves (P<0.001). There was no significant difference between the diameters of the ICA flow voids adjacent to the atrophic optic nerves versus either the study group's contralateral ICA flow voids (P=0.91) or the control group's ICA flow voids (P=0.74).
Conclusions: The authors speculate that the intimate relation between the optic nerve and adjacent ICA may be important in the development of unexplained optic neuropathy. The ICA need not appear abnormal in MRIs.