Primary Visual Cortical Thickness Correlates with Visual Field Defects in Patients with Pituitary Macroadenomas: A Structural 7-Tesla Retinotopic Analysis

Introduction: Vision loss remains a debilitating complication of pituitary adenomas, although there is considerable variability in visual impairment before and after decompression surgery. Growing evidence suggests secondary damage to remote visual structures may contribute to vision loss in patients with chiasmatic compression. The present study leverages ultrahigh field 7-T MRI to study the retinotopic organization of the primary visual cortex (V1), and correlates visual defects with cortical thinning in V1 to characterize consequences of pituitary adenomas on the posterior visual system.

Methods: Eight patients (four males, mean age = 44.3 years) with pituitary adenomas, and eight matched healthy controls (four males, mean = 43.3 years) were scanned at 7-T MRI for prospective study. Whole-brain cortical thickness was calculated using an automated algorithm. A previously published surface-based algorithm was applied to associate the eccentricity and polar angle with each position in V1 ([Fig. 1]). Cortical thickness was calculated at each point in the retinotopic organization, and cortical thickness ratio was generated against matched controls for each point in the visual fields. Adenoma patients additionally underwent neuroophthalmological examination including 24–2 Humphrey’s automated visual field perimetry. Pattern deviation (PD) of each point in the visual field, the deviation in point-detection compared with normals, was correlated with cortical thickness at corresponding polar and eccentricity angles in V1.

Results: Whole-brain cortical thickness was successfully derived for all patients and controls. The mean tumor volume was 19.4 cm³. The median global thickness of V1 did not differ between patients (mean ± SD = 2.21 ± 0.12 cm), compared with controls (2.06 ± 0.13 cm), p > 0.05. Surface morphometry-based retinotopic maps revealed that all eight adenoma patients showed a significant positive correlation between PD and V1 thickness ratios (r-values range, 0.31–0.46), p < 0.05 ([Figs. 2] and [3]). Mixed procedure analysis revealed that PD = −8.0719 + 5.5873 × (median V1 thickness ratio).

Conclusion: All eight patients showed significant positive correlations between V1 thickness and visual defect. These findings provide retinotopic of localized V1 cortical neurodegeneration spatially corresponding to impairments in the visual field ([Fig. 4]). These results further characterize changes in the posterior visual pathway associated with chiasmatic compression, and may prove useful in the neuroophthalmological workup for patients with pituitary macroadenoma.