thumb| Areas affected in Mixed Transcortical Aphasia
Mixed transcortical aphasia is the least common of the three transcortical aphasias (behind transcortical motor aphasia and transcortical sensory aphasia, respectively). This type of aphasia can also be referred to as "Isolation Aphasia". This type of aphasia is a result of damage that isolates the language areas (Broca's, Wernicke's, and the arcuate fasciculus) from other brain regions. Broca's, Wernicke's, and the arcuate fasiculus are left intact; however, they are isolated from other brain regions. Following a stroke, 40% of stroke patients are left with moderate functional impairment and 15% to 30% have a severe disability as a result of a stroke. A neurogenic cognitive-communicative disorder is one possible result of a stroke, with neuro- meaning related to nerves or the nervous system and -genic meaning resulting from or caused by. Aphasia is one type of a neurogenic cognitive-communicative disorder which presents with impaired comprehension and production of speech and language, usually caused by damage in the language-dominant, left hemisphere of the brain.
Symptoms and language characteristics
Mixed transcortical aphasia is characterized by severe speaking and comprehension impairment, but with preserved repetition. People who suffer mixed transcortical aphasia struggle greatly to produce propositional language or to understand what is being said to them, yet they can repeat long, complex utterances or finish a song once they hear the first part. Persons with mixed transcortical aphasia are often nonfluent, and in most cases do not speak unless they are spoken to, do not comprehend spoken language, cannot name objects, and cannot read or write. However, they often have the ability to repeat what is said to them. In fact, persons with mixed transcortical aphasia often repeat in a parrot-like fashion.
A conversation between a clinician and person with transcortical mixed aphasia would have similar characteristics to the conversation below: This damage isolates these areas from the rest of the brain. The most frequent etiology of mixed transcortical aphasia is stenosis (narrowing) of the internal carotid artery. Mixed transcortical aphasia can also occur after cerebral hypoxia, cerebral swelling, and any stroke that affects the cerebral artery. Often lesions that cause mixed transcortical aphasia affect both the anterior and posterior perisylvian border zones. Some times the type of aphasia can be determined just by knowing the lesion location. Using WAB or the BDAE can rule out global aphasia if the ability to repeat is present. The study conducted on drawing therapy found that it increased naming abilities in patients with acute and chronic aphasia. It also produced fewer error attempts during naming tasks. The gains made from drawing therapy were not ones that could have been made from spontaneous recovery. Drawing therapy has proved to be effective even after a few periods of therapy.
Although this therapy is aimed at patients with aphasia, it can be implemented for any patient with expressive deficits. Patients with mixed transcortical aphasia demonstrate similar deficits as those seen in patients with global aphasia. Therefore, assessment of repetition is most critical in order to differentially diagnose. Specifically, language based standardized assessments such as the Western Aphasia Battery (WAB), and the Folstein Mini Mental State Exam include a repetition subtest amongst all other language-related areas.
Other possible assessments that can provide further differentiation include:
Magnetic Resonance Imaging (MRI)
Magnetic Resonance Angiography (MRA)
CT scan
Informal observation
It is important to remain diligent in providing therapy regardless of aphasia classification.
Prognosis
If brain damage is minimal then a patient may recover language skills over time without treatment, however if the damage is severe it may be necessary to receive speech and language therapy. Internal factors are factors related to the stroke such as aphasia severity, lesion site and lesion size . Individuals with milder forms of aphasia, lesions that insignificantly impact language function and smaller lesions tend to have a higher degree of aphasia recovery. Lesions in the superior temporal gyrus (STG) produce a more persistent global aphasia, which is associated with poor aphasia recovery. Patient specific factors relate to the patient's age of onset, education level and motivation for recovery. Younger patients have been reported to demonstrate a higher recovery rate than older patients. Those with more years of education are less vulnerable to language disruption by stroke.