TRANSCORTICAL MOTOR APHASIA: SYMPTOMS, CAUSES AND TREATMENT - NEUROPSYCHOLOGY - 2025

The transcortical motor aphasia arises from an injury that leaves intact the perisylvian areas of language and its connections, but also isolates associative brain areas. The association areas establish connections between the sensory and motor zones and are in charge of integrating and interpreting the information that comes from these areas, giving it meaning.

This language disorder is characterized by a decrease in spontaneous speech, however, he understands well what is said as long as it is not too complex. The funny thing is that these types of patients cannot answer when asked for their name, but they can repeat practically any sentence fluently.

History

The origin of this type of aphasia is associated with the German Ludwig Lichtheim, who dealt with this subject in his work "Über Aphasie" in 1885. He introduced the so-called "center of concepts" (called B) which was essential to understand aphasia transcortical.

Until now, only the auditory image centers (we called it A) and the motor images (we called it M) of words were known. The center of the concepts added by this author was necessary for people to understand language while being able to speak spontaneously, of their own free will.

It would be associated with Wernicke's area (focused on the auditory aspect of words and understanding of language) and with Broca's area (focused on the motor aspect of words and expression of speech).

Thus:

- When there is a lesion in the AB pathway, that is to say, in the connections between the auditory center of the words and the center of the concepts, there was incomprehension of the language, the patient being able to repeat sentences by the other pathway. It gives rise to transcortical sensory aphasia: which affects understanding.

- When there is a lesion in the MB pathway, or in the motor connections of language and the conceptual center, there is a decrease in spontaneous speech, although the patient can repeat sentences. It results in transcortical motor aphasia, which we describe here, and affects language production.

Although Lichtheim uses the word "center," this does not mean that it has a single, delimited location in the brain; Rather, it is the result of a combination of the activity of various areas of the cerebral cortex. It even indicates that it can be widely located throughout the hemisphere.

Wernicke and the bell

Wernicke later described a good example to understand what Lichtheim proposed:

To understand the word “bell”, the information from the posterior temporal cortex (A) activates in the brain the different images that we associate with “bell” that are registered in the cortex in different places depending on whether they are: acoustic images (such as different sounds of bells), visual (shape, color of a bell), tactile (hardness, temperature, texture) and motor (hand movements associated with ringing a bell).

These images are linked together and all form the concept of the hood. This concept is also represented in motor images, which gives rise to the movements necessary to verbally pronounce "bell".

Causes of transcortical motor aphasia

Norman Geschwind studied a case of this type of aphasia, examining the brain post mortem.

He found a large bilateral lesion (in both hemispheres) in the cortex and the white matter, leaving the perisylvian cortex, the insula, the occipital lobe, and other areas intact. So the damage cut off the language areas of the rest of the cortex and preserved more Wernicke and Broca areas, as well as the connections between them.

This then means that the language comprehension and production areas are preserved, but it is not enough. Connections with other parts of the brain are needed for language to function satisfactorily, being able to memorize and retrieve the meanings of words.

Transcortical motor aphasia is usually due to ischemia in the left middle cerebral artery or nearby areas that may involve the anterior cerebral artery. It usually appears from a stroke in the anterior superior frontal lobe of the dominant hemisphere for language (usually the left).

Types

According to Berthier, García Casares and Dávila there are 3 types:

Classic

At first, it can occur with muteness or speech with very little fluency. Later, they only emit isolated words or automatic phrases.

In addition, they articulate correctly and the grammar is adequate, although with a low volume of the voice and no melody. The concepts or categories are altered, while they repeat smoothly.

They do not present paraphasias or problems of understanding or naming. This subtype is also characterized by echolalia and ability to complete sentences.

Dynamic (or adynamic) aphasia

It is characterized by the absence of the initiative to speak, by having a deficit in the strategies in the lexical and semantic search or by not knowing how to choose between several verbal responses. Instead, comprehension, naming, and repetition are intact.

Atypical

The same as the classical one, but when the lesion spreads in other regions (right hemisphere, Broca's area, sensorimotor cortex…) other different symptoms occur. For example: problems with articulation or listening comprehension, stuttering, etc.

It is important not to confuse transcortical motor aphasia with akinetic mutism, since the latter is due to frontal brain damage that causes a state of apathy or demotivation in the patient that prevents them from initiating behaviors, including language.

What is its prevalence?

According to the Copenhagen Aphasia Study, out of 270 cases of aphasia, only 25 patients (9%) had transcortical aphasia. Specifically, 2% were of the motor type. On the other hand, when more time has passed after the injury (during the first month after the damage), transcortical motor aphasia is more frequent (8%) than sensory (3%).

In short, it is a group of rare aphasic syndromes that ranges between 2% and 8% of the diagnoses of aphasia in acute phases.

Symptoms

This type of aphasia can result from the evolution of Broca's aphasia or global aphasia. According to Hanlon et al. (1999) a type of aphasia called global aphasia without hemiparesis, seems to precede transcortical motor aphasia in some cases. Thus, the symptoms of transcortical motor aphasia appear in more advanced stages, being rare that they appear immediately after the injury.

Depending on the places that the brain damage occupies, it will manifest different symptoms. For example, they may present typical symptoms of prefrontal lesions (disinhibition, impulsivity or apathy).

Main symptoms:

- He speaks little, with difficulty, without prosody (without intonation, rhythm or speed control).

- Emit only short sentences with poor grammatical structure.

- Fluent and adequate verbal repetition, although it is limited to not very long sentences. The longer the sentence, the more mistakes they make. This serves as a differentiation from other types of aphasia, so that if the recurrence is preserved, the definitive diagnosis of transcortical motor aphasia can be made.

- Uncontrollable and involuntary echolalia.

- The naming capacity is altered to different degrees according to each patient and is influenced by environmental clues and phonetic clues (sounds of language).

- Reading comprehension is practically preserved. They can even read aloud with few errors, which is very surprising in aphasic patients.

- On the other hand, it presents alterations in the writing.

- May show deficits in right motor capacity, usually partial hemiparesis.

- In some cases there is also ideomotor apraxia, which means the inability to program the sequence of voluntary movements necessary to properly use objects (such as brushing teeth with a brush or sweeping with a broom), in addition to the so-called transitive movements (making gestures like saying goodbye with your hand) or intransitives (imitating movements or postures that are indicated).

What is your prognosis?

A good prognosis is estimated, and there are authors who have observed a significant recovery after one year, seeing progress very early.

Even after a few weeks, patients are able to answer questions vastly better than at the beginning. Little by little the speech and the less common paraphasias become more frequent. They also gain in grammatical structure, although the sentences are still short.

As we said, it is common for patients with Broca's or global aphasia to evolve to this type of aphasia. However, the location and extent of the lesion, age, educational level, gender, motivation, and available support influence the course of the disease.

How is the patient evaluated?

Here are some recommendations for evaluating a patient who is suspected of this type of aphasia:

- Comprehensive assessment of language skills.

- Examine other cognitive functions to see their status and rule out other causes: attention, memory or executive functions.

- Try to choose or design tests in which language can be measured without affecting the difficulties in language production that these patients have.

- A good test to establish the diagnosis is the Boston Test for the Diagnosis of Aphasia (TBDA), which measures the state of various linguistic aspects: language fluency, listening and reading comprehension, naming, reading, writing, repetition, automated speech (reciting) and music (singing and rhythm).

- A large number of very diverse tests can be used to assess other aspects such as attention, memory, visuospatial functions, praxis, executive functions, etc.

A good professional will know how to combine the tests and program them in the best way to evaluate the patient in the most correct way without causing the patient to become fatigued and frustrated.

Thanks to these results, it is possible to find out the conserved capacities that can be strengthened, and which ones are damaged and must be worked on to recover or alleviate them.

Treatments

The treatment of transcortical motor aphasia depends largely on how affected or not other cognitive functions that we have mentioned before are.

Requirements for therapy

For therapy to work, the person with aphasia must be able to maintain attention and concentrate. In addition, you will need to learn new strategies, so you must have a minimum of skills associated with memory.

On the other hand, it is also essential that they preserve executive functions, since without them they will not be able to generalize knowledge, be flexible or apply it to other environments. If, on the other hand, compensatory communication techniques such as drawing or writing have to be trained, the visual-perceptual skills must be intact.

In other words, if any of these basic abilities are impaired, you must first try to rehabilitate those abilities to lay the foundations for a good later recovery of the language.

How to rehabilitate damaged capacities?

For this, it can be worth reducing incorrect or persistent answers that will act as a barrier to speaking properly.

How is it done? Well, first, the patient has to be aware of his mistakes in order to correct them. This is made easy through naming tasks (naming objects, animals…). If you miss a lot in the same word, it can be good for the person to learn to put the wrong word written and crossed out in a place where they will see it.

If you can't say the word, clues can be provided; like the first letter you start with, say the definition of the word or use gestures to represent it.

In cases where it is not possible, the specialist can say the stimulus out loud and ask the patient to repeat it.

The creation of new grammatical constructions can also be encouraged through photos, short stories or sentences that the patient has to try to describe or answer some questions about. They try to add new adjectives and use different types of phrases (interrogative, declarative, comparative…)

Other tasks are aimed at generating ideas on a certain topic. You can propose to the person to tell topics that interest you and answer questions about it, or you can put texts, videos or images on the topic to help them.

Importance of metacognition

Increased motivation, self-control, self-awareness, and maintenance of goal-directed behaviors are important. This is called metacognition and it is very helpful in keeping and spreading what has been learned in treatment.

Intensity

In a study by Bhogal et al. (2003), the maximum effects of the intervention if performed intensively (8 hours a week for 2 or 3 months) were highlighted.

Drugs

There is research that supports the success of bromocriptine, a dopamine agonist drug, which seems to enhance the positive results of the intervention in patients with transcortical motor aphasia. Its function is to increase the number of neural networks to help the emission of verbal expression in patients who do not speak fluently.

References

1. Berthier, M., García Casares, N., & Dávila, G. (2011). Update: Aphasias and speech disorders. Accredited Continuing Medical Education Program, 10 (Diseases of the nervous system), 5035-5041.
2. Bhogal, SK, Teasell, R., & Speechley, M. (2003). Stroke: Intensity of aphasia therapy, impact on recovery. American Heart Association Inc., 34, 987-993.
3. Geschwind N., Quadfasel FA, Segarra JM (1968). Isolation of the speech area. Neuropsychology, 327-40.
4. Hanlon, R., Lux, W., & Dromerick, A. (1999). Global aphasia without hemiparesis: language profiles and lesion distribution. Journal Of Neurology Neurosurgery And Psychiatry, 66 (3), 365-369.
5. Nieto Barco, AG (2012). Transcortical motor aphasia. In MB Arnedo Montoro, Neuropsychology. Through clinical cases. (pp. 163-174). Madrid: Panamerican Medical.
6. Pulvemüller, F. & Bethier, ML (2008). Aphasia therapy on a neuroscience basis. Aphasiology, 22 (6), 563-599.
7. Rogalsky, C., Poppa, T., Chen, K., Anderson, SW, Damasio, H., Love, T., & Hickok, G. (2015). Speech repetition as a window on the neurobiology of auditory – motor integration for speech: A voxel-based lesion symptom mapping study. Neuropsychologia, 71, 18-27.
8. Thompson, CK (2000). Neuroplasticity: Evidence from aphasia. Journal Of Communication Disorders, 33 (4), 357-366.