Atypical conduction aphasia. A disconnection syndrome
M. F. Mendez and D. F. Benson
Conduction aphasia was originally proposed to result from separation of the
posterior language comprehension area and the anterior motor speech area of
the left hemisphere. The arcuate fasciculus has been the most frequently
suggested site of such a disconnection, but the syndrome has been reported
in cases in which the abnormality involved the dominant Wernicke's area.
This challenges the arcuate fasciculus theory, and it has been suggested
that a cortical lesion, not a disconnection, is the crucial factor. Three
new cases in which the lesion does not lie in the arcuate fasciculus are
reported, two in left-handed patients with left temporoparietal lesions and
one in a right-handed patient with a right temporoparietal infarct, a
"crossed" aphasia. While atypical, these cases offer evidence that
disconnection of the circuit linking language comprehension to motor speech
output, not damage to a specific cortical region, underlies the syndrome of
conduction aphasia.
