Introduction: To clarify the relationship between visual disturbances caused by pituitary adenomas and the degree of chiasmal compression, MRI (1.5T) findings were assessed two dimensionally.
Material and methods: 50 cases of pituitary adenomas and 17 control cases were studied. The position of the optic chiasm was measured by the distance from the line of the frontal base and posterior clinoid process on the sagittal T1 weighted image, and from the upper surface of the bilateral internal carotid artery on the coronal T1 image.
Result: Visual disturbances appeared when the chiasm was displaced to more than 8 mm above the aforesaid reference level on the sagittal image and more than 13 mm above on the coronal image. There was a good correlation between the appearance of visual field defects and the degree of chiasmal compression.
Conclusion: The degree of chiasmal displacement measured by MRI two dimensionally can provide useful information for predicting the appearance of visual disturbances.