Supplementary motor area syndrome: characteristics, symptoms and causes.

This neurological disorder is characterized by its total reversibility, as it does not leave serious sequelae.

The supplementary motor area is a region located in the frontal lobe of the brain, responsible for functions such as the initiation, preparation and coordination of motor actions, as well as other processes related to language.

When a part of this brain area is removed or injured, motor motor area syndrome can occur, supplementary motor area syndrome can occur.. In this article we explain what it is and what are the main characteristics of the supplementary motor area syndrome and the brain region that is affected by it. We also tell you the clinical signs and symptoms it causes, and how to make a differential diagnosis of this disorder.

The supplementary motor area: characteristics, location and functions

To understand what the supplementary motor area syndrome consists of, we must first delve into the characteristics and main functions of such an important brain region as the supplementary motor area.

This brain region is located in the medial aspect of the frontal lobe.. It extends posteriorly to the primary motor cortex and inferiorly to the cingulate gyrus. It belongs to Brodmann's area 6 and is part of the motor cortex, and more specifically, of the secondary motor cortex (together with the premotor area).

Researchers have divided the supplementary motor area, at least, into two distinct parts: the presupplementary motor area, which is responsible for initiating movements in response to external and environmental stimuli; and the supplementary motor area itself, whose functions include managing the initiation of internally generated voluntary motor sequences.

The supplementary motor area is, as mentioned above, a key region for initiating motor actions, but it also plays an important role in the motivation necessary to initiate motor sequences. has an important role in the motivation necessary for movement to occur.. This also occurs with the processes involved in speech, since the activation of this area is also essential to initiate verbal communication acts.

On the other hand, activation of the supplementary motor area occurs when complex motor sequences requiring fine and precise movements are carried out (e.g., when the motor area is involved in the initiation of verbal communication). sewing by hand or drawing). In addition, several studies have shown that this area is also activated when we imagine that we are performing a specific movement, although it is not carried out.

In studies carried out with subjects who have suffered lesions in this brain area, it has been shown that when the damage occurs in the left supplementary motor area, transcortical motor aphasia usually occurs, which is characterized by a deficit in comprehension and understanding of the brain. characterized by a deficit in the comprehension of language, both verbal and written, although, on the other handThe patient, on the other hand, maintains some verbal fluency.

Another of the disorders related to damage in this region of the brain, which will be discussed in this article, is the supplementary motor area syndrome. Let us see what it consists of.

What is supplementary motor area syndrome?

Supplementary motor area syndrome is a disorder resulting from surgical resection or injury to the brain region that bears its name.. It was Laplane, who in 1977 described the clinical evolution of the supplementary motor area syndrome in patients who had undergone resective surgery.

This researcher observed that lesions in the supplementary motor area produced a characteristic syndrome that evolves in three stages:

1. after surgery and resection of the supplementary motor area; 2. after surgery and resection of the supplementary motor area; 3. after surgery and resection of the supplementary motor area.

The patient, immediately after surgery and resection of the supplementary motor area, experiences global akinesia (more pronounced on the contralateral side) and language arrest..

2. A few days after recovery

The patient, within a few days of recovery after surgery, experiences a severe reduction of motor activity (more pronounced on the contralateral side) and language arrest. severe reduction of spontaneous motor activity on the contralateral side, facial paralysis and spontaneous speech reduction..

3. Time after surgery

Some time after resective surgery, the patient will have long-term sequelae which include the alteration of fine and precise hand movements, such as alternating movements, especially in complex tasks.

Characteristics and main symptoms

The main characteristic of the supplementary motor area syndrome is its transient nature and its complete reversibility, which can occur in a period of time that is usually less than 6 months.. The patient recovers automatic movements before voluntary ones, which is logical if we take into account that the supplementary motor area is dominated by the management of internally generated movements (without external stimulation), as opposed to motor actions initiated from external stimuli.

The patient's recovery is based on neuronal plasticity mechanisms that facilitate the transfer of information from the supplementary motor area to its contralateral counterpart. However, the patient will experience clinical signs and symptoms that will last for a long time, the patient will experience clinical signs and symptoms that will last as long as it takes for recovery to be completed..

The supplementary motor area syndrome generates comic seizures, which provoke tonic postures that include flexion of the contralateral elbow, abduction of the arm with external rotation of the shoulder, as well as cephalic and ocular deviation. These seizures usually last a few seconds (between 5 and 30) and are characterized by being quite frequent, without auras, with a sudden onset and end, and predominate during the patient's sleep and when vocalizing.

Transcortical motor aphasia occurs in practically all cases in which the lesion occurs in the dominant hemisphere.It has been shown in several studies that the majority of patients also have severe hemiparesis with motor neglect.

Language disorders in people affected by supplementary motor area syndrome have the following features:

• Hypofluent language, with dysnomia and slowing (the cause of which is motor transcortical anomia).
• Repetition and comprehension are preserved.
• Telegraphic language.
• Rarely, paraphasia occurs.
• Occasionally, echolalia and perseveration may be present.

Differential diagnosis

The differential diagnosis of patients with Supplementary Motor Area Syndrome (SAMS) is usually made with individuals presenting with immediate postoperative motor deficits and lesions of the corticospinal tract.The differential diagnosis is usually made with patients with immediate postoperative motor deficits and lesions of the corticospinal tract, which is characterized by increased Muscle stretch reflexes, in contrast to SAMS.

In some cases, the motor deficit could be considered a motor neglect, rather than a hemiparesis, as verbal stimuli often elicit a motor response from the affected hemibody.In many cases, verbal stimuli elicit a motor response from the affected hemisphere. Recovery of SAMS includes the involvement of the non-injured hemisphere, in which SAMS takes a preponderant role to start relearning movements.

Bibliographic references:

• Krainik A et al. Postoperative speech disorder after medial frontal surgery. Role of the supplementary motor area. Neurology 2003; 60: 587-94.
• Nachev, P., Kennard, C., & Husain, M. (2008). Functional role of the supplementary and pre-supplementary motor areas. Nature Reviews Neuroscience, 9(11), 856.
• Rajshekhar, U. B. V. (2000). Post operative supplementary motor area syndrome: clinical features and outcome. British journal of neurosurgery, 14(3), 204-210.