A Possible Case of Transient Anton’s Syndrome Status Post Bilateral Occipital Lobe Infarct

To the Editor: We present, with enthusiasm, a probable yet transient case of Anton’s Syndrome (AS), status post (S/P)-bilateral right occipital lobe infarct.

Our patient is a 63-year-old white woman with longstanding coronary artery disease who was transferred from another facility for a coronary artery bypass graft. After her surgery, she presented with an altered mental status, including confusion and agitation, which prompted a noncontrast Computed Tomography (CT) scan of the head. The CT showed an acute-to-subacute right occipital infarct, and follow-up Magnetic Resonance Imaging of the head with and without contrast displayed bilateral occipital lobe infarcts. Pupillary reflexes were intact, and neurological examination was otherwise within normal limits. The patient seemed to demonstrate prosopagnosia (only able to name her family members by voice). The patient showed signs consistent with blindness, including being unable to locate utensils in front of her. When asked to name objects, patient would confabulate by saying that a pen was a fish or that a television was a burning fireplace, often not looking at the object. While our patient demonstrated the ability to correctly identify family members 5 days after her cerebrovascular accident (CVA), it wasn’t until 10 days S/P CVA, that both her sight and AS markedly improved, and, by 2 weeks S/P CVA, she had full visual acuity without any residual AS.

AS is a rare form of anosognosia where persons are either partially or totally blind, but deny visual impairment,¹ despite evidence that they are indeed blind. AS is a type of cortical blindness due to occipital cortex compromise,² but it can also affect visual association cortex. These damaged visual association areas are effectively disconnected from functioning areas, such as speech-language areas. In the absence of input, functioning speech areas often confabulate a response.¹

This disorder is most commonly, although not always,^2,3 the result of bilateral occipital cortex ischemia due to insufficiency of the posterior blood vessels.⁴ In addition to the hypothesized disconnection described above, two other likely neuropsychological mechanisms have been postulated. One suggests that the monitor of visual stimuli is defective and is incorrectly interpreting images. The other suggests the presence of false feedback from another visual system. In this regard, the superior colliculus, pulvinar, and temporo-parietal regions may transmit signals when the geniculocalcarine system fails. In the absence of visual input, this false internal imagery may convince speech areas to come out with a response.¹

Similar to our patient, some can recover their sight fully, and others show little-to-no improvement in sight. There is evidence that by weeks-to-months poststroke, some reorganization of structure/function relationships may occur. Thus, the typically transient behavioral presentation is most likely a reflection not only of infarcted tissue, but also of surrounding, hypoperfused tissue.⁵

Thus, we feel it is prudent to consider AS in patients with visual disturbances where there has been an insult to occipital cortex.