Transcortical motor aphasia

Transcortical motor aphasia (TMoA), also known as commissural dysphasia or white matter dysphasia, results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output, which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions, although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this, individuals with TMoA often present with difficulty in speech maintenance and initiation. Transcortical motor aphasia (TMoA), also known as commissural dysphasia or white matter dysphasia, results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output, which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions, although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this, individuals with TMoA often present with difficulty in speech maintenance and initiation. Damage in the watershed region does not directly harm the areas of the brain involved in language production or comprehension; instead, the damage isolates these areas from the rest of the brain. If there is damage to the frontal lobe, executive functions related to language use are often affected. Executive functions relevant to language include activating language responses, controlling syntax (grammar), and narrative discourse. Difficulties in these areas can lead to supplementary deficits involving difficulties forming complex sentences, choosing which words to use appropriately, and initiating speech in conversation. The extent and location of the brain damage will impact the degree and variety of language functioning characteristics (i.e. damage deep to the frontal lobe and/or damage across multiple regions will greatly impair language). Right hemiparesis, or right-sided paralysis, may coincide with TMoA if the lesion in the anterior frontal lobe is large enough and extends into the posterior frontal lobe. There are some other forms of aphasia that relate to TMoA. For instance, adynamic aphasia is a form of TMoA that is characterized by sparse speech. This occurs as a result of executive functioning in the frontal lobe. Another form of aphasia related to TMoA is dynamic aphasia. Patients with this form of aphasia may present with a contiguity disorder in which they have difficulty combining linguistic elements. For dynamic aphasia, this is most apparent when the patient is asked to sequence at the sentence level whereas for other aphasias contiguity disorder can be seen at the phoneme or word level. TMoA is classified as a non-fluent aphasia that is characterized by a significantly reduced output of speech, but good auditory comprehension. Auditory comprehension skills remain intact because the arcuate fasciculus and Wernicke's area are not impaired. Individuals with TMoA also exhibit good repetition skills and can repeat long, complex phrases effortlessly and without error. However, spontaneous speech often presents with paraphasias (a term used to describe a wide variety of speech errors that are caused by aphasia). Regardless of any relative communication strengths, individuals with TMoA are typically poor conversational partners. Due to damage in the anterior superior frontal lobe, people with TMoA have deficits in initiation and maintenance of conversations, which results in reduced speech output. A person with TMoA may seldomly produce utterances and typically remain silent. The utterances that they do produce are typically only one to two words long. However, in more structured and predictable interactions, individuals with TMoA tend to respond more fluently and promptly. In addition, these individuals are characterized by their attentiveness and cooperation and are often described as being task-oriented. Neurological imaging has shown that TMoA is typically caused by an infarct of the anterior superior frontal lobe in the perisylvian area of the left, or language-dominant, hemisphere. The anterior superior frontal lobe is known as the prefrontal cortex which is responsible for the initiation and ideation of verbal speech. The damage leaves the major language networks, Broca's and Wernicke’s areas and the arcuate fasiculus, unaffected. Brain injury can result from a stroke caused by left anterior cerebral artery (ACA) occlusion, brain tumors, traumatic brain injury (TBI), or progressive neurological disorders. TMoA is diagnosed by the referring physician and speech-language pathologist (SLP). The overall sign of TMoA is nonfluent, reduced, fragmentary echoic, and perseverative speech with frequent hesitations and pauses. Patients with TMoA also have difficulty initiating and maintaining speech. However, speech articulation and auditory comprehension remain typical. The hallmark sign of TMoA is intact repetition in the presence of these signs and symptoms. TMoA, or any other type of aphasia, is identified and diagnosed through the screening and assessment process. Screening can be conducted by a SLP or other professional when there is a suspected aphasia. The screening does not diagnose aphasia, rather it points to the need for a further comprehensive assessment. A screening typically includes evaluation of oral motor functions, speech production skills, comprehension, use of written and verbal language, cognitive communication, swallowing, and hearing. Both the screening and assessment must be sensitive to the patient's linguistic and cultural differences. An individual will be recommended to receive a comprehensive assessment if their screening shows signs of aphasia. Under the American Speech-Language-Hearing Association (ASHA) and World Health Organization (WHO) guidelines and the International Classification of Functioning, Disability and Health (ICF) framework, the comprehensive assessment encompasses not only speech and language, but also impairments in body structure and function, co-morbid deficits, limitations in activity and participation, and contextual (environmental and personal) factors. The assessment can be static (current functioning) or dynamic (ongoing) and the assessment tools can be standardized or nonstandardized. Typically, the assessment for aphasia includes a gathering of a case history, a self-report from the patient, an oral-motor examination, assessment of expressive and receptive language in spoken and written forms, and identification of facilitators and barriers to patient success. From this assessment, the SLP will determine type of aphasia and the patient's communicative strengths and weaknesses and how their diagnosis may impact their overall quality of life. Treatment for all types of aphasia, including transcortical motor aphasia, is usually provided by a speech-language pathologist. The SLP chooses specific therapy tasks and goals based on the speech and language abilities and needs of the individual. In general for individuals with TMoA, treatment should capitalize on their strong auditory comprehension and repetition skills and address the individual's reduced speech output and difficulty initiating and maintaining a conversation. New research in aphasia treatment is showing the benefit of the Life Participation Approach to Aphasia (LPAA) in which goals are written based on the skills needed by the individual patient to participate in specific real-life situations (i.e. communicating effectively with nurses or gaining employment). Based on the specific needs of the patient, SLPs can provide a variety of treatment activities.