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NBME 24 Answers

nbme24/Block 4/Question#48

A 55-year-old woman is brought to the physician by ...

Posterior cerebral

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submitted by lsmarshall(203),

PCA stroke can cause "prosopagnosia" which is the inability to recognize familiar faces. Caused by bilateral lesions of visual association areas, which are situated in the inferior occipitotemporal cortex (fusiform gyrus). The ability to name parts of the face (e.g., nose, mouth) or identify individuals by other cues (e.g., clothing, voices) is left intact.

Without knowing that, remembering occipital lobe is involved in 'visual stuff' broadly, including image processing and this patient is having issues with understanding images should be enough to get to the answer.

gonyyong  Lol I guessed it exactly because of that +1  
sympathetikey  Never heard of that one before. Thanks! +1  
karthvee  This is not prosopagnosia, but instead a case of apperceptive agnosia. Wiki: "...patients are more effective at naming two attributes from a single object than they are able to name one attribute on each of the two superimposed objects. In addition they are still able to describe objects in detail and recognize objects by touch." Although, lesions tend to be in the occipito-parietal area so PCA again is the answer! +1  

 +2  upvote downvote
submitted by sweetmed(41),

PCA stroke: Visual Agnosia [can see, but not recognize objects] and Hallucinations, Contralateral hemianopia with macular sparing, Alexia without agraphia[if dominant hemispehere involved].

Lesions of the Temporal Lobe:

Superior temporal gyrus: Acoustic agnosia (patient cannot differentiate between sounds) Middle temporal gyrus: Movement agnosia (patient cannot differentiate between the moving and stationary object) Inferior temporal gyrus: supplied by PCA 1. Prosopagnosia (inability to identify the faces) 2. Achromatopsia (loss of color sensation and everything appears gray to them)