The Chiasmal Compression Index: An Integrative Assessment Tool for Visual Disturbances in Patients with Pituitary Macroadenomas

OBJECTIVE: Visual status is routinely evaluated by neuro-ophthalmologic examination and computerized visual field (VF) tests in patients with chiasmal compression secondary to pituitary macroadenoma. Currently, no relevant data exists to accurately quantify the extent of optic apparatus compromise to further guide clinical decision-making. We aimed to assess for a possible quantitative correlation between optic chiasm geometric properties on magnetic resonance imaging (MRI) and VF deficits.METHODS: Visual assessments and concurrent MRI scans were retrospectively reviewed from patients treated for pituitary macroadenoma in a single medical institution. Chiasm width, chiasm minimal and maximal height, and chiasm angle were measured on MRI coronal plane images by 3 independent reviewers (for the sake of variability analysis). VF numerical summary parameters were also retrieved.RESULTS: A total of 30 patients were included in the final analysis. Average VF index was 70% (30), and averaged mean deviation was 10.0 db (+/- 9). Chiasm angle and width (which together represents the bending and stretching of the chiasm by the upward directed compression; both of which demonstrated high interand intraobserver agreement) showed strong correlation with VF loss. Chiasmal compression index derived from those parameters showed even stronger correlation.CONCLUSIONS: The strong correlation demonstrated by our results of this relatively simple radiologic measurement with VF status, despite the relatively small cohort,calls for further investigation in this promising direction, and may facilitate with basic assessment and clinical decision-making for patients with equivocal neuro-ophthalmologic evaluation, as well as with poor compliance.