Functional MRI Combined with Perimetry to Identify Visual Field Defects in the Stroke-Damaged Brain

Article: New research gives hope for sight recovery in stroke survivors
Source: University of Nottingham (U.K.)
Published: January 6, 2022

Anatomical lesion locations for each participant

Every year 150,000 people in the U.K. have a stroke, with approximately 30% experiencing some kind of vision loss as a result. Perimetry is the gold standard for assessing residual visual field coverage; however, it has limitations such as requiring attention and cooperation from participants and only providing coarse and indirect information about the location of visual field deficits along the visual pathway. Scientists in the U.K. explored the use of functional magnetic resonance imaging (fMRI), combined with clinical perimetry, to more precisely map visual brain areas affected by vision loss in four stroke survivors (two cases of homonymous hemianopia and two cases of homonymous quadrantanopia), with the hopes that identification of such areas could provide a more complete picture of vision loss and potentially improve rehabilitation of function. Additionally, the study employed measurements from population receptive fields (pRF), lesion definitions from anatomical scans, and white matter tracts from diffusion weighted MRI data to better map the anatomy, connectivity, and function of the visual pathway after stroke. PhD student and lead author of the study explains, "A common misconception with stroke-related sight loss is that it affects vision through a particular eye. What is actually happening is that the eyes are seeing normally but the brain can’t process some of the information." The use of fMRI revealed residual activity in the visual cortex not detected by perimetry. These areas of "residual vision" are places where the brain can still process images, even if it doesn't reach awareness. The more precise mapping of fMRI also showed that the same patterns of visual field defects can result from different patterns of brain damage. Senior author of the study comments, "Using MRI to pinpoint these areas of functional vision, clinicians could work with the stroke survivor and train them to recover some function in that particular spot." The research aims to give much-needed hope to those experiencing vision loss as a devastating complication of cerebral strokes, in turn reminding us of the value of sight.

My rating of this study: ⭐🌸

Beh A, McGraw PV, Webb BS, et al. "Linking Multi-Modal MRI to Clinical Measures of Visual Field Loss After Stroke." Frontiers in Neuroscience.  5 January 2021. https://doi.org/10.3389/fnins.2021.737215