In Part 1 we introduced you to Ruth and her conundrum in trying to read. She has a condition known as Alexia Sine Agraphia, popularized by Oliver Sacks, and chronicled by Howard Engel in his book, The Man Who Forgot How To Read. Ruth has become a member of a club that she had no interest in joining. As a retired school teacher who specialized in teaching children how to read, her condition was not debilitating to her career as it was for Howard Engel, the Canadian mystery novel writer. How did Ruth wind up with this condition? The narrative of her MRI report on February 2, 2012 provides the clues. Here are the key findings:
“Multifocal areas of abnormal restricted diffusion are evident within the left posterior cerebral artery territory, consistent with multifocal acute/early subacute infarctions involving the left paramedian occipital lobe, posterior medial left temporal lobe, involving a portion of the left hippocampal formation, and also involving the left aspect of the splenium of the corupus callosum, which is supplied typically by the posterior pericallosal artery derived from the posterior cerebral artery”.
Wow! No one does run-on sentences like dictating radiologists, but you can get the gist of the problem as we take another look at the textbook photo we introduced in Part 1.
The large arrow in the right occipital lobe shows that the flow of information is intact on that side. However, disruption of the paraventricular white matter and the outflow of the corpus callosum (C.C.) impedes the visual information (small arrow) from accessing the angular gyrus in the language area. As you go back and re-read the radiologist’s narrative, think of the evidence pointing toward the existence of a visual word form area in the posterior part of the left midfusiform gyrus in the occipitotemporal region of the brain, as championed by Dehaene. While the most common cause of alexia sine agraphia is a posterior cerebral artery distribution stroke, it has also been reported in association with intracerebral hemorrhages, A-V malformations, tumors, encephalitis, and even migraine. As if we needed it, yet another reminder of just how fra-gile we are.