Hemiparesis is a deficit of muscular strength, that is to say an incomplete paralysis which causes a decrease in the capacities of movements. This lack of muscle strength can reach the right side of the body, or the left side.

It is one of the frequent consequences of neurological diseases, foremost among which is stroke, the incidence of which is increasing in the world population due to the increase in life expectancy. Effective treatment currently tends to combine mental practice with motor rehabilitation.

Definition of hemiparesis

Hemiparesis is most often found in a context of neurological disease: it is an incomplete paralysis, or a partial deficit in muscle strength and movement capacities, which affects only one side of the body. We thus speak of left hemiparesis and right hemiparesis. This slight paralysis can affect the whole of the hemibody (it will then be a proportional hemiparesis), it can also affect only one part of the arm or the leg, or of the face, or even involve several of these parts. (in these cases it will be a non-proportional hemiparesis).

Causes of hemiparesis

Hemiparesis is most often caused by a dysfunction of the central nervous system. The main cause of hemiparesis is stroke. Thus, cerebrovascular accidents lead to sensorimotor deficits, resulting in hemiplegia or hemiparesis.

There is also, in children, hemiparesis caused by a lesion of the part of the brain, during pregnancy, during childbirth or quickly after birth: this is congenital hemiparesis. If hemiparesis occurs later in childhood, then it is called acquired hemiparesis.

It turns out that injury to the left side of the brain can cause right hemiparesis, and conversely, injury to the right side of the brain will cause left hemiparesis.

Diagnostic

The diagnosis of hemiparesis is clinical, in the face of reduced movement capacities on one of the two sides of the body.

The people concerned

The elderly are more at risk of stroke, and therefore more affected by hemiparesis. Thus, due to the extension of the lifespan of the world’s population, the number of people affected by stroke has increased substantially in recent years.

Risk factors

The risk factors for hemiparesis may, in fact, correlate with the risk of presenting a pathology linked to neurological dysfunction, and particularly with the risk of developing a stroke, which are:

• the tobacco ;
• the alcohol ;
• obesity;
• physical inactivity ;
• high blood pressure ;
• hypercholesterolemia;
• heart rhythm disturbances;
• diabetes ;
• the stress ;
• and age …

Partial motor deficit of the hemibody

Hemiparesis, generated by an original cause often neurological, is in itself more a symptom than a pathology, its clinical sign is very visible since it corresponds to a partial motor deficit of the hemibody.

Difficulty walking

If the lower body is affected, or one of the two legs, the patient may have difficulty in exerting movements of that leg. These patients will therefore have difficulty walking. The hip, ankle and knee also often present abnormalities, affecting the gait of these people.

Difficulty performing arm movements

If one of the two lower limbs is affected, right or left arm, it will have difficulty in performing movements.

Visceral hemiparesis

The face can also be affected: the patient will then present a slight facial paralysis, with possible speech disorders and swallowing difficulties.

Other symptoms

• contractions ;
• spasticity (tendency of a muscle to be contracted);
• selective reduction of engine control.

With the aim of reducing motor deficits and accelerating the functional recovery from the uses of limbs or parts of the body deficient, mental practice, combined with motor rehabilitation, has been introduced within the rehabilitation process of patients who have undergone stroke.

• This rehabilitation based on daily activities is more effective than conventional motor rehabilitation;
• This combination of mental practice and motor rehabilitation has proven its usefulness and effectiveness, with significant results, markedly improving motor deficits, including hemiparesis, in patients following stroke;
• Future studies will allow more specific parameters of the duration or frequency of these exercises to be determined with precision.

Lighting: what is mental practice?

Mental practice consists of a method of training, where the internal reproduction of a given motor action (ie mental simulation) is repeated extensively. The intention is to promote the learning or improvement of motor skills, by mentally imagining the movement to be performed. 

This mental stimulation, also called motor image, corresponds to a dynamic state during the performance of a specific action, which is reactivated internally by the working memory in the absence of any movement.

Mental practice therefore results in conscious access to motor intention, usually accomplished unconsciously during preparation for movement. Thus, it establishes a relationship between motor events and cognitive perceptions.

Functional magnetic resonance imaging (fMRI) techniques have also shown that not only the additional premotor and motor areas and the cerebellum were activated during the imagined movements of the hand and fingers, but also that the primary motor area the opposite side was also busy.

Preventing hemiparesis amounts, in fact, to preventing neurological diseases and cerebrovascular accidents, and therefore to adopting a healthy lifestyle, by not smoking, by having regular physical activity and a balanced diet in order to avoid develop, among other things, diabetes and obesity.