Alexia Without Agraphia

The patient is a 69 year old left handed man with a history of hypertension, insulin dependent diabetes mellitus and atrial fibrillation. Treated with coumadin, adjusted to keep the INR between 2 and 3. On the morning of admission he awoke at 4 a.m., sat momentarily on the side of the bed and then stood up and walked without difficulty a distance of ten feet before falling to the ground. His wife found him disoriented and mildly confused. He told her that he could only see half of her face. On examination in the ER, he had rapid atrial fibrillation (127 beats per minute) and an elevated blood pressure 215/128, which quickly fell to a stable level of 150/90. He was alert and oriented to Mass General Hospital and to the month, but gave the year incorrectly as 1992. His attention fluctuated. On memory testing he had a diminished five-minute recall for a name, address and flower, and recall for well known events through which he had lived, for example, John F. Kennedy assassination. He could not recall the names of the last five Presidents. He followed one-step commands correctly. His speech was normal apart from minor errors naming objects. His reading was severely impaired (alexia). He was unable to recognize written words on the page and had difficulty with most single letters when presented visually. In contrast, when words were spelled out to him, he could recognize them without difficulty and his ability to spell was intact. His writing was fluent when asked to spontaneously write a description of the weather and also correct on dictation with no spelling errors. He was asked to write his name and address which he did correctly, and three words, house, rose and mountain. He wrote the words correctly and was then distracted for approximately 5 minutes and asked to re-read them. He was unable to read the words out loud. When the patient listened to the spelling of these words out loud, he was able to identify the word correctly. He was unable to read single letters. Color Vision: He was given the Ishihara pseudo-isochromatic test of color vision and performed it without error, as he could read single and two digit numbers or he traced them out correctly with his finger. Color Anomia: He was unable to name colors correctly (color anomia). When shown different colored bottle caps, he was able to name red and blue correctly but called green purple and yellow orange. He matched two red objects correctly. He was able to identify famous faces and had no visual disorientation (simultanagnosia). Neuro-ophthalmological Examination: Visual acuity of 20/60 or better, (making errors reading the Snellen chart) Automated perimetry: dense right homonymous hemianopia (Figure 1). Pupils, ocular motility and fundus examination normal Neurological Examination: •A slight right facial weakness with blunting of the nasolabial fold •A mild right hemiparesis with right drift •Mild hyperreflexia on the right with an extensor plantar response •No sensory extinction, apraxia, astereognosis, or agraphesthesia. A chest x-ray showed cardiomegaly. EKG atrial fibrillation with normal axis. MRI with diffusion weighted imaging (DWI), a bright lesion in the left thalamus and internal capsule consistent with an infarct in the distribution of the posterior choroidal vessels. The new stroke presentation was characterized by: •Alexia without agraphia •A dense right homonymous hemianopia •Color anomia Repeat MRI with DWI showed a new left occipital lobe infarct in the distribution of the left P2 division of the posterior cerebral artery (PCA). (Figure 2-5). The MRI supported the diagnosis of a disconnection syndrome affecting connections involved in naming a seen object and in reading. Disconnection Syndrome: With destruction of the left visual cortex and splenium (or intervening white matter), words perceived in the right visual cortex cannot cross over to the language areas and the patient cannot read. Figure 3 shows diagrammatically how a visual pattern is transferred from the visual cortex and association areas to the angular gyrus, which arouses the auditory pattern in the Wernicke area. The auditory pattern is transmitted to Broca's area, where the articulatory form is aroused and transferred to the contiguous face area of the motor cortex. Diagnosis: Embolic infarct of the left visual cortex and spenium of the corpus callosum with a dense right homonymous hemianopia Disconnection Syndrome Alexia without agraphia Color anomia Pure alexia. See also: http://content.lib.utah.edu/cdm/ref/collection/ehsl-shw/id/110