The Transcortical motor aphasia Arises from an injury that leaves intact the perisilvian areas of language and their connections, but at the same time isolates them from the associative brain areas. The areas of association establish connections between the sensitive and motor zones and are responsible for integrating and interpreting the information that comes from these areas, giving it meaning.

This disorder of language is characterized by a decrease in spontaneous speech, however, it understands well what is said whenever it is not very complex.

The funny thing is that these types of patients can not answer when asked their name, but they can repeat almost any sentence with fluency.

How did it come about?

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

So far we only knew the centers of auditory images (we call it A) and the motor images (we call it M) of the words. The core of the concepts that this author added was necessary for people to understand the language while being able to speak spontaneously, of their own volition.

And it would be associated with both Wernicke area (Focusing on the auditory aspect of words and understanding of language) and with the Broca area (Centered on the motor aspect of words and expression of speech).

Thus:

- When there is an injury in the A-B pathway , That is, in the connections between the auditory center of the words and the center of the concepts, the language was incomprehensible and the patient could repeat sentences in the other way. It results in transcortical sensory aphasia: it affects comprehension.

- When there is an injury on the M-B track , Or in the motor connections of the language and the conceptual center, there is a decrease of the spontaneous speech, although the patient can repeat statements. It results in transcortical motor aphasia, which we describe here, and affects the production of language.

Although Lichtheim uses the word"center", this does not mean that it has a unique and limited location in the brain; But is rather the result of a combination of activity in several areas of the Cerebral cortex . It even indicates that it can be widely located throughout the hemisphere.

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

In order to understand the word"bell", the information of the posterior temporal cortex (A) activates in the brain the different images that we relate with"bell"that are registered in the cortex in different places depending on: acoustic images (like different sounds of Bells), visual (shape, color of a bell), tactile (hardness, temperature, texture) and motor (movements of the hand associated with ringing a bell).

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

Here is an example of how this model would be structured. B means the center of concepts, M the center of motor representations and A the center of the auditory representations of language. As we can see, B has different subtypes: B1, B2, B3... this means that concepts are distributed widely throughout the brain.

The"a"minuscule would represent the brain structure that receives the language heard and the"m"structure that makes it possible for us to emit movements for speech.

Causes of transcortical motor aphasia

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

It found a large bilateral lesion (in both hemispheres) in the cortex and white matter, leaving intact the perisilvian cortex, the Insula , he occipital lobe , And other areas. So that the damage left incommunicado the areas of the language of the rest of the cortex and conserved more areas of Wernicke and of Broca, in addition to the connections between them.

This means that the areas of language and production understanding are preserved, but not enough. Connections to other parts of the brain So that the language works satisfactorily, reaching to memorize and recover the meanings of the 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. Usually appears due to a stroke in the Frontal lobe Superior of the dominant hemisphere for language (usually the left).

Types

According to Berthier, Garcia Casares and Dávila (2011) there are 3 types:

Classical

At first, it can be accompanied by mutism or language with very little fluency. Later on, they only utter isolated words or automatic phrases.

In addition, they articulate correctly and the grammar is adequate, although with a low volume of the voice and without melody. The concepts or categories are altered while repeating without problems.

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

Dynamic (or adynamic) aphasia

It is characterized by the absence of the initiative to speak, because there is a deficit in strategies in the lexical and semantic search or not know how to choose between several verbal responses. On the other hand, understanding, naming and repetition are intact.

Atypical

Same as the classic one, but when the lesion extends in other regions (right hemisphere, Broca area, sensorimotor cortex...), there are other different symptoms. For example: problems in the 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 him from initiating behaviors, including language.

What is its prevalence?

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

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

symptom

This type of aphasia can result from the evolution of a Aphasia of Broca Or aphasia of a global type. 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, symptoms of transcortical motor aphasia appear in more advanced phases, being rare that they appear immediately after the injury.

According to the places that occupy the brain damage, it will manifest different symptoms. For example, they may have typical symptoms of prefrontal injury (disinhibition, impulsivity, or apathy).

Main symptoms:

- Speak scarce, with difficulty, without prosody (without intonation, neither rhythm nor control of speed).

- Output only short sentences with poor grammatical structure.

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

- Ecolalia Uncontrollable and involuntary.

- The capacity of denomination is altered in different degrees according to each patient and receives influence of the tracks of the environment and the phonetic keys (sounds of the 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.

- It may show deficits in the right motor capacity, usually a partial hemiparesis.

- In some cases, ideomotor apraxia also occurs, which means the inability to program the sequence of voluntary movements necessary to properly use objects (such as brushing with a brush or sweeping a broom), as well as so-called transitive movements Like saying goodbye with the hand) or the intransitive (imitate movements or postures that are indicated to him).

What is your forecast?

It is estimated a good prognosis, with authors who have observed a significant recovery after one year, seeing the advances very early.

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

As we said, it is common for patients with Broca 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 (Thompson, 2000).

How is the patient evaluated?

Here are some recommendations for evaluating a patient suspected of having 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 the language production of these patients.

- A good test to establish the diagnosis is the Boston Test for Diagnosis of Aphasia (TBDA), which measures the state of several 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 right way without fatigue and frustration.

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

Treatments

It depends to a great extent on whether or not there are other cognitive functions that we have named before.

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

On the other hand, it is also essential that they retain the 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, you need to train compensatory communication techniques such as drawing or writing, you need the skills visoperceptivas are intact.

That is to say, if any of these basic capacities are damaged, we must first try to rehabilitate those capacities to lay the foundations for a good later recovery of the language.

To do so may be the reduction of incorrect or persevering answers that will serve as a barrier to speak adequately.

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, animalsâ?? |). If you miss much in the same word, it may be good for the person to learn to place the wrong word written and crossed out in a place where the person sees it.

If you can not say the word, you can provide clues; As the first letter by which it begins, say the definition of the word or use gestures that represent it.

In cases where it is not achieved, the specialist can say the stimulus aloud and ask the patient to repeat it.

You can also encourage the creation of new grammatical constructions through photos, small stories or statements that the patient has to try to describe or answer some questions about it. He tries to add new adjectives and use different types of sentences (interrogative, declarative, comparative...)

Other tasks are aimed at generating ideas on a certain topic. It can be proposed to the person who says topics that interest him and that answers questions about it, or texts, videos or images on the subject that help him.

Important Increased motivation , Self-control, self-knowledge, and the maintenance of goal-directed behaviors. This is called metacognition and is very useful for staying and spreading what has been learned in treatment.

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

There is research that supports the success of Bromocriptine , An agonist drug of the Dopamine , Which seems to enhance the positive results of the intervention in patients with transcortical motor aphasia (Pulvemüller & Bethier, 2008). Its function is to increase the number of neural networks to aid 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 Training Program, 10 (Nervous System Diseases), 5035-5041.
2. Bhogal, S.K, Teasell, R., & Speechley, M. (2003). Stroke: Intensity of aphasia therapy, impact on recovery. American Heart Association Inc., 34, 987-993.
3. Geschwind N., Quadfasel F.A., Segarra J.M. (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, A. G. (2012). Transcortical motor aphasia. In M. B. Arnedo Montoro, Neuropsychology. Through clinical cases. (Pages 163-174). Madrid: Pan American Medical.
6. Pulvemüller, F. & Bethier, M. L. (2008). Aphasia therapy on a neuroscience basis. Aphasiology, 22 (6), 563-599.
7. Rogalsky, C., Poppa, T., Chen, K., Anderson, S. W., 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. Neuropsychology, 71, 18-27.
8. Thompson, C.K. (2000). Neuroplasticity: Evidence from aphasia. Journal Of Communication Disorders, 33 (4), 357-366.