How robust is the optic chiasm? Perimetric and neuro-imaging correlations.
OBJECTIVE
Analysis of form and function relationships with tumour-mediated dislocations and deformations of the optic chiasm.


METHODS
Results of magnetic resonance tomography and two forms of quantitative, computerized perimetry were contrasted in 31 patients with pituitary adenomata impinging on the chiasm, prior to treatment.


RESULTS
Perimetric abnormalities ranged from none to modest. High-pass Resolution Perimetry (HRP) produced abnormal results in 10 cases and RareBit perimetry (RBP) in 15 cases. Overall, field defects and qualitative stages of deformation and dislocation of the chiasm were well correlated. Among quantitative indices, the best correlations were obtained by a measure of the cranio-caudal position of the chiasm.


CONCLUSIONS
On average, an elevation of the chiasm by 6 mm will be associated with abnormal visual fields in 50% of the cases. An additional elevation of 5 mm will raise the incidence of field defects to 90%.
Frisén
L
L
Institute of Neuroscience and Physiology, Section of Neurological Sciences and Rehabilitation, and Institute of Clinical Sciences, Section of Radiology, The Sahlgrenska Academy, Göteborg University, Sweden. lars.frisen@neuro.gu.se
Jensen
C
C
D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009897:Optic Chiasm / Q000473:pathology* / Q000503:physiopathology; D019574:Optic Nerve Neoplasms / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D010911:Pituitary Neoplasms / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology