A woman in her early 50s presented with 2 months of progressive cognitive impairment and visual loss. Her visual acuity was reduced to hand movements bilaterally and she was unable to read numbers or trace lines on Ishihara plates. Her flash and pattern electroretinogram and occipital pattern visual evoked potentials results were normal. Coronal fluid-attenuated inversion recovery magnetic resonance imaging (MRI) scans showed extensive confluent symmetrical occipital predominant white matter abnormalities (Figure 1A).