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Transcortical Motor Aphasia or isolation of speech syndrome (TMA) results from injury along the border of thefrontal-parietal-occipital lobesThe injury is typically caused by a cerebrovascular accident (CVA), commonly referred to as a stroke. The area of insult is sometimes referred to as a watershed region, a region surrounding Broca's area. The insult typically involves the left hemisphere as most people (regardless of handedness) are left hemisphere dominant for language (nearly 100% of right-handers, about 85% of left-handers). TMA is a less common impairment than Broca's aphasia.
- Language loss can be total.
- Where function is retained speech is non-fluent (halting and effortful) and their utterances are typically only one or two words long.
- People with TMA generally have good comprehension since Wernicke's area is usually not affected.
- People with TMA may only retain the ability to repeat words, phrases or sentences [[Echolalia] and show no other language skill.
- Repetition is preserved since the arcuate fasciculus (the neural pathway that connects Wernicke’s and Broca’s areas via the parietal lobe) is intact. Preserved repetition is a defining quality of all transcortical aphasias.
- People who suffer from transcortical motor aphasia, however, may experience delays in initiation when they try to repeat words due to damage in the frontal lobe.
As writing ability parallels speaking ability, it follows that people who suffer from TMA have severely impaired writing ability. As writing is a secondary modality (learned through formal instruction in grade school) it is always more severely affected than a primary modality like speaking.
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