[Unilateral visual field defect due to optic nerve compression by sclerotic internal carotid artery: a case report]

A case of unilateral visual field defect due to optic nerve compression by a sclerotic internal carotid artery was reported. A 71-year-old woman was admitted to our department because of constricted visual field of the right eye. MRI showed elevation of the right optic nerve compressed by an internal carotid artery. The right carotid angiography revealed elevation and distortion of the C1-2 portion. Frontal craniotomy was carried out and the optic nerve was visualized on this side. The right optic nerve was found to have been compressed by the sclerotic internal carotid artery. The optic canal was then unroofed. The post-operative course was uneventful. The visual field was improved. When last seen 6 months after surgery, her visual field remained in the improved condition. Nasal field abnormalities are most frequently encountered in retinal and anterior optic nerve pathology. Our success in improving the visual field disturbance may be accounted for by the fact that the preoperative period was short and the operation was performed before atrophy of ocular fundi occurred. Nasal field loss caused by intracranial lesions of the optic pathway is rare. It is probably impossible to determine degree of the symptomatology caused by direct-pressure compression as opposed to that caused by ischemia secondary to occlusion of small arterial supply branches. Vascular compressive neuropathy of optic nerve should not be diagnosed simply by the radiological finding of the optic nerve dislocation. However, optic nerve compression by surrounding arteries should be remembered as one of the possible causes of visual field defect which needs to be treated surgically.