Introduction: Pituitary adenomas are known to comprise the optic apparatus, and the evaluation of vision loss for these patients continues to be a clinical and diagnostic challenge [1,2]. Diffusion-weighted 7 Tesla MRI (dMRI) and structural imaging were used to evaluate secondary damage of the visual pathway by pituitary adenomas. dMRI allows for mapping of white matter microstructure in vivo [3]. Imaging was correlated with neuro-ophthalmological results to assess the utility of ultra high-field MRI for objective evaluation of damage to the visual pathways.

Methods: Probabilistic tractography using 7 Tesla dMRI (1.05-mm isotropic) was used to reconstruct the optic tracts and radiations (Figure 1) in 18 patients with adenomas and 16 controls. MP2RAGE (0.7-mm isotropic) and T2-TSE (0.4x0.4x2-mm) sequences were also acquired. Diffusion indices were calculated along the tracts and radiations and correlated with tumor volumes and results from neuro-ophthalmological examinations. Optic nerve sheath diameters (ONSD) and primary visual cortical (V1) thicknesses were also assessed.

Results: The main group differences between patients and controls are summarized in Figure 2. Pattern standard deviation (PSD) scores positively correlated with tumor volume (r=0.89,p=0.004), and MD of the optic tracts (r=0.87, p = 0.006) and radiations (r=0.69,p=0.05). PSD was anti-correlated with FA of the tracts(r=-0.73,p=0.05). Mean deviation positively correlated with FA of the tracts(r=0.81,p=0.016), and negatively correlated with MD of the tracts (r=-0.88,p=0.008). Correlations between tumor volume and dMRI are shown in Figure 3.

Conclusions: We demonstrated significant damage in otherwise normal-appearing white matter of the anterior and posterior visual pathways in pituitary adenoma patients. Imaging-based quantification of secondary neuronal damage strongly correlated with neuro-ophthalmological findings. dMRI offers a promising method of i) objective grading of existing damage to the visual pathway to determine indication for surgical decompression and ii) predicting the considerable variability [4] in visual recovery post-surgery, serving as a pre-operative marker of vision recoverability.

Patient Care: The methods and results presented in this work may improve the grading of tumor impact on visual function since neither conventional MRI nor neuro-ophthalmological examination can probe microstructure. Additionally, our findings suggest that ultra-high field dMRI may be useful in predicting vision recoverability, and may serve as a prognostic marker.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of employing ultra-high field MRI to assess secondary pathology from pituitary adenomas ,2) Discuss the subtle microstructure damage in the visual pathways caused by suprasellar lesions and 3) Recognize the utility of diffusion MRI's ability to precisely predict vision impairment in patients with pituitary adenomas.

References: 1. Boland MV, Lee IH, Zan E, Yousem DM, Miller NR: Quantitative Analysis of the Displacement of the Anterior Visual Pathway by Pituitary Lesions and the Associated Visual Field Loss. Invest Opthalmol Vis Sci 57:3576-80, 2016 2. Ho RW, Huang HM, Ho JT: The Influence of Pituitary Adenoma Size on Vision and Visual Outcomes after Trans-Sphenoidal Adenectomy: A Report of 78 Cases. J Korean Neurosurg Soc 57:23-31, 2015 3. Le Bihan D, Mangin JF, Poupon C, Clark CA, Pappata S, Molko N, et al: Diffusion tensor imaging: Concepts and applications. J Magn Reson Imaging 13:534-46, 2001 4. Laws ER, Trautmann JC, Hollenhorst RW Jr: Transsphenoidal decompression of optic-nerve and chiasm—visual results in 62 patients. J Neurosurg 46:717–722, 1977