Quantitative assessment of secondary white matter injury in the visual pathway by pituitary adenomas: a multimodal study at 7-Tesla MRI

Abstract

OBJECTIVEThe objective of this study was to investigate microstructural damage caused by pituitary macroadenomas by performing probabilistic tractography of the optic tracts and radiations using 7-T diffusion-weighted MRI (DWI). These imaging findings were correlated with neuro-ophthalmological results to assess the utility of ultra–high-field MRI for objective evaluation of damage to the anterior and posterior visual pathways.METHODSProbabilistic tractography employing 7-T DWI was used to reconstruct the optic tracts and radiations in 18 patients with adenomas and in 16 healthy volunteers. Optic chiasm compression was found in 66.7% of the patients and visual defects in 61.1%. Diffusion indices were calculated along the projections and correlated with tumor volumes and results from neuro-ophthalmological examinations. Primary visual cortical thicknesses were also assessed.RESULTSFractional anisotropy was reduced by 21.9% in the optic tracts (p < 0.001) and 17.7% in the optic radiations (p < 0.001) in patients with adenomas. Patients showed an 8.5% increase in mean diffusivity of optic radiations compared with healthy controls (p < 0.001). Primary visual cortical thickness was reduced in adenoma patients. Diffusion indices of the visual pathway showed significant correlations with neuro-ophthalmological examination findings.CONCLUSIONSImaging-based quantification of secondary neuronal damage from adenomas strongly correlated with neuro-ophthalmological findings. Diffusion characteristics enabled by ultra–high-field DWI may allow preoperative characterization of visual pathway damage in patients with chiasmatic compression and may inform prognosis for vision recoverability.

Diffusion Tensor Imaging and Neurite Orientation Dispersion and Density Imaging Assessment of Optic Pathway Function in Patients With Anterior Visual Pathway Compression

“…In addition, considering the reversibility of visual field defect after the surgery, edema or gliosis might be one of contributing factors. Our results were similar to a few previous studies that reported transsynaptic degeneration in sellar or parasellar lesions (1,17). Changes of DTI and NODDI parameters in the optic radiation may reflect transsynaptic degeneration, which has been reported as a mechanism of secondary pathology in the posterior visual pathways in conditions that primarily affect the anterior visual pathway, such as glaucoma (18,19) and optic neuritis (20,21).…”

Empty Sella Syndrome as a Window Into the Neuroprotective Effects of Prolactin

“…Crush and stretch injuries to the optic nerve, tract and chiasm in animals reveal that demyelination is a primary process in the progression of delayed axonal degeneration ( 1 – 4 ). Human studies looking at compression of the optic chiasm have confirmed those findings and also suggested the possibility of rapid vision recovery ( 5 , 6 ). Unlike primary axotomy, in which axonal connections are immediately severed, delayed axonal degeneration is a potentially reversible process.…”

Empty sella syndrome as a window into the neuroprotective effects of prolactin

“…Crush and stretch injuries to the optic nerve, tract and chiasm in animals reveals that demyelination is a primary process in the progression of delayed axonal degeneration (1-4). Human studies looking at compression of the optic chiasm have confirmed these findings and also suggested the possibility of rapid vision recovery (5,6). Unlike primary axotomy, in which axonal connections are immediately severed, delayed axonal degeneration is a potentially reversible process.…”