[Vascular compression neuropathy of the optic nerve by sclerotic internal carotid artery]

Although mechanical compression of the optic nerve by a dilated and/or tortuous sclerotic intracranial internal carotid artery is occasionally reported as an etiology for impairment of vision and visual field, early diagnosis of such condition has been hampered by the lack of characteristic neuro-ophthalmological and neuroradiological findings. The review of 35 previously reported cases (60 eyes) including ours showed that 41% out of the 34 operated eyes were improved neurologically by the decompressive procedure, while it was in 27% out of the 26 undecompressed or non-operated eyes. These unsatisfactory operative results are considered mainly due to the failure of early diagnosis. In order to investigate the relationship between the carotid artery and optic nerve, we proposed a method of angiographical projection consisting of the straight view along the long axis of the optic canal. By this projection, it is possible to detect a supero-medial enlargement and/or dislocation of the cisternal portion of the internal carotid artery. The addition of metrizamide CT cisternography which clarifies the relationship of the optic nerve, chiasm and internal carotid artery in the supersellar cistern may further provide an useful clue for the diagnosis of this condition.