Transcortical motor aphasia
Transcortical motor aphasia is different than Broca's aphasia in that repetition ability is intact. Patients who demonstrate transcortical motor ahasia have the same halting, agrammatic speech of Broca's, but may be echolalic, or able to repeat complex words and phrases.
The speech pattern of these patients is characterized by halting, nonfluent patterns with frequent literal and verbal paraphasias. Auditory comprehension may also be impaired to some extent, but they can usually carry on a simple conversation. Lesions which produce transcortical motor aphasia spare Broca's area and extend either anteriorly or superiorly deep into the underlying white matter or in the cortex.
Here is a T2 weighted MRI of a patient who suffered from Transcortical motor aphasia. It comes from the Whole Brain Atlas at Harvard University Medical School. The patient's left is on the right. As you can see, the lesion is in the left temporal lobe and left frontal cortex, sparing the prerolandic areas.
This is caused by damage in the cortical areas around Broca's area, but sparing the arcuate fasciculus and Wernicke's area. These patients often tend not to speak spontaneously, and may speak only when given strong urging from those around them. When they speak, their speech is fluent and well-articulated, but sparse. Their utterances are often one to two words long, and complete sentences are rare. However, they can repeat long and complex sentences with little trouble (they just can't initiate them). Auditory comprehension is good.
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