Predictors for visual dysfunction in nonfunctioning pituitary adenomas - implications for neurosurgical management.

BACKGROUND: Despite ample experience with surgical treatment of nonfunctioning pituitary adenomas, objective data defining the risk for visual compromise depending on the suprasellar extension in pituitary adenomas are sparse. DESIGN AND PATIENTS: We measured the suprasellar extension of 98 newly diagnosed suprasellar nonfunctioning pituitary adenomas on sagittal and coronal magnetic resonance images using reference lines for the skull base level. In addition, the position of the optic chiasm in relation to the suprasellar adenoma was assessed. The findings were correlated with the degree of visual dysfunction and with the type of visual field defects (VFD).
RESULTS: Seventy per cent of the patients suffered from VFD. The most frequent perimetric findings were bilateral (81·2%) or unilateral (10·1%) temporal hemifield defects. For the coronal view, a suprasellar extension of 12 mm was a practicable cut-off value for emergence of visual disturbances (87·0% sensitivity, 72·4% specificity). For the sagittal view, 8-mm suprasellar extension was a suitable cut-off for appearance of chiasma syndrome (87·0% sensitivity, 75·9% specificity). In five of seven cases without a chiasma syndrome despite a suprasellar extension >12 (coronal) and 8 mm (sagittal), the optic chiasm was found in an anterior position. No correlation was found between the position of the chiasm (i.e. anterior, superior or posterior) and the type of VFD (P = 0·647). A highly significant correlation was found between the decline of visual acuity and the suprasellar adenoma extension (P < 0·0001).
CONCLUSION: Cut-off values possess a high sensitivity and specificity for imminent visual disturbances and are helpful for clinical decision-making. A delayed emergence of visual dysfunction may be observed with an anterior position of the optic chiasm.