Neuroimaging and cognitive correlates of retinal Optical Coherence Tomography (OCT) measures at late middle age in a twin sample

Type 2 Diabetes and Biomarkers of Brain Structure, Perfusion, Metabolism, and Function in Late Mid-Life: A Multimodal Discordant Twin Study

BACKGROUND

Type 2 diabetes (T2D) is associated with an increased risk of dementia and early features may become evident even in mid-life. Characterizing these early features comprehensively requires multiple measurement modalities and careful selection of participants with and without T2D.

OBJECTIVE

We conducted a cross-sectional multimodal imaging study of T2D-discordant twins in late mid-life to provide insights into underlying mechanisms.

METHODS

Measurements included computerized cognitive battery, brain MRI (including arterial spin labelling, diffusion tensor, resting state functional), fluorodeoxyglucose (FDG)-PET, and retinal optical coherence tomography.

RESULTS

There were 23 pairs, mean age 63.7 (±6.1) years. In global analyses, T2D was associated with poorer attention (β= -0.45, p <0.001) and with reduced FDG uptake (β= -5.04, p = 0.02), but not with cortical thickness (p = 0.71), total brain volume (p = 0.51), fractional anisotropy (p = 0.15), mean diffusivity (p = 0.34), or resting state activity (p = 0.4). Higher FDG uptake was associated with better attention (β= 3.19, p = 0.01) but not with other cognitive domains. In regional analyses, T2D was associated with lower accumbens volume (β= -44, p = 0.0004) which was in turn associated with poorer attention.

CONCLUSION

T2D-related brain dysfunction in mid-life manifests as attentional loss accompanied by evidence of subtle neurodegeneration and global reduction in cerebral metabolism, in the absence of overt cerebrovascular disease.

Optical Coherence Tomography: Retinal Imaging Contributes to the Understanding of Brain Pathology in Classical Galactosemia

It remains unresolved whether central nervous system involvement in treated classical galactosemia (CG) is a progressive neurodegenerative process. This study aimed to investigate retinal neuroaxonal degeneration in CG as a surrogate of brain pathology. Global peripapillary retinal nerve fibre layer (GpRNFL) and combined ganglion cell and inner plexiform layer (GCIPL) were analysed in 11 CG patients and 60 controls (HC) using spectral-domain optical coherence tomography. Visual acuity (VA) and low-contrast VA (LCVA) were acquired to test visual function. GpRNFL and GCIPL did not differ between CG and HC (p > 0.05). However, in CG, there was an effect of intellectual outcome on GCIPL (p = 0.036), and GpRNFL and GCIPL correlated with neurological rating scale scores (p < 0.05). A single-case follow-up analysis showed GpRNFL (0.53-0.83%) and GCIPL (0.52-0.85%) annual decrease beyond the normal aging effect. VA and LCVA were reduced in CG with intellectual disability (p = 0.009/0.006), likely due to impaired visual perception. These findings support that CG is not a neurodegenerative disease, but that brain damage is more likely to occur early in brain development. To clarify a minor neurodegenerative component in the brain pathology of CG, we propose multicenter cross-sectional and longitudinal studies using retinal imaging.

Blood flow perfusion in visual pathway detected by arterial spin labeling magnetic resonance imaging for differential diagnosis of ocular ischemic syndrome

Background

Ocular ischemic syndrome (OIS), attributable to chronic hypoperfusion caused by marked carotid stenosis, is one of the important factors that cause ocular neurodegenerative diseases such as optic atrophy. The current study aimed to detect blood flow perfusion in a visual pathway by arterial spin labeling (ASL) and magnetic resonance imaging (MRI) for the differential diagnosis of OIS.

Methods

This diagnostic, cross-sectional study at a single institution was performed to detect blood flow perfusion in a visual pathway based on 3D pseudocontinuous ASL (3D-pCASL) using 3.0T MRI. A total of 91 participants (91 eyes) consisting of 30 eyes with OIS and 61 eyes with noncarotid artery stenosis-related retinal vascular diseases (39 eyes with diabetic retinopathy and 22 eyes with high myopic retinopathy) were consecutively included. Blood flow perfusion values in visual pathways derived from regions of interest in ASL images, including the retinal-choroidal complex, the intraorbital segments of the optic nerve, the tractus optics, and the visual center, were obtained and compared with arm-retinal circulation time and retinal circulation time derived from fundus fluorescein angiography (FFA). Receiver operating characteristic (ROC) curve analyses and the intraclass correlation coefficient (ICC) were performed to evaluate the accuracy and consistency.

Results

Patients with OIS had the lowest blood flow perfusion values in the visual pathway (all p < 0.05). The relative intraorbital segments of optic nerve blood flow values at post-labeling delays (PLDs) of 1.5 s (area under the curve, AUC = 0.832) and the relative retinal-choroidal complex blood flow values at PLDs of 2.5 s (AUC = 0.805) were effective for the differential diagnosis of OIS. The ICC of the blood flow values derived from the retinal-choroidal complex and the intraorbital segments of the optic nerve between the two observers showed satisfactory concordance (all ICC > 0.932, p < 0.001). The adverse reaction rates of ASL and FFA were 2.20 and 3.30%, respectively.

Conclusion

3D-pCASL showed that the participants with OIS had lower blood flow perfusion values in the visual pathway, which presented satisfactory accuracy, reproducibility, and safety. It is a noninvasive and comprehensive differential diagnostic tool to assess blood flow perfusion in a visual pathway for the differential diagnosis of OIS.