What Are Extrapyramidal Side Effects?

The extrapyramidal system is a component of the human motor system. Its main function is to regulate muscle tension and coordinate movement and balance of muscles. This regulatory function depends on the dynamic balance of the central neurotransmitters dopamine and acetylcholine. When dopamine is reduced or acetylcholine is relatively increased, symptoms of cholinergic nerve hyperactivity may occur, increased muscle tone, dull faces, and slow movements. Parkinson's syndrome-like symptoms such as tremor, muscle tremor, salivation; acute dystonia, compulsive mouth opening, tongue extension, torticollis, dyskinesia, and dysphagia; inability to sit still, with restlessness and repeated wandering; There is a triad of mouth-tongue-cheek, such as sucking, licking tongue, chewing, etc. This is the extrapyramidal response.

Chinese name: Extrapyramidal response
Belong to: Human motion system

Features: Adjust muscle tone and maintain body movement
Depends on: Homeostasis of Dopamine and Acetylcholine

Extrapyramidal reaction

The nerve cells and conductive fibers that control the movement of the human body are mainly divided into the cone system (consisting of pyramidal cells in the motor cortex of the cerebral cortex and the conductive fibers in the cortical spinal cord and cortical brain stem bundles) and extrapyramidal systems.

Except for the pyramidal tract, all other motor nucleus and motor conduction tracts are extrapyramidal. After the extrapyramidal system originated from the cerebral cortex, they first connected with the striatum on the way down, and then reached the motor neurons in the anterior horn of the spinal cord after multiple replacements. The cerebral and cerebellar circuits formed between the cerebral cortex and the cerebellar cortex are important for regulating and affecting the voluntary movement initiated by the cerebral cortex.

Both the cone system and the extrapyramid system are inseparable and their functions are consistent. The extrapyramidal structure is complex and involves many structures in the brain, including the cerebral cortex, striatum, dorsal thalamus, hypothalamus, apical gyrus, red nucleus, substantia nigra, pontine nucleus, vestibular nucleus, cerebellum, and brain stem network Like motor structures, these motor nucleus groups not only have intricate fiber connections, but also receive fibers in the cerebral cortex motor area or inhibition area, and then return to the cerebral cortex motor area through the old and new striatum and thalamus to form a return. Loop. The body movement is adjusted through a complex loop to ensure that the cone system performs fine random movements. The main loops are: 1) Cortex-striatum-Paleum-thalamus loop. 2) Pale sphere-hypothalamus loop. 3) Nigro-striatum loop. 4) Pale bulb-thalamus-striatum loop.

The main physiological functions of extrapyramidal response

The main physiological functions of extrapyramidal system:

1) Prepare for the random movement of the cone system;

2) adjust muscle tension;

3) Maintain the body's movement posture;

4) Related to involuntary movement accompanied by voluntary movement;

5) Controls the reflection of the lower motor neurons. Because the above-mentioned main functions of the extrapyramidal system are to adjust the posture, muscle tension, and coordinate muscle movements of the human body to assist in the completion of voluntary movements, when the disease occurs, it directly and indirectly affects voluntary movements and produces various clinical symptoms.

In general, it can be summarized into two categories: increased muscle tone-reduced exercise syndrome and decreased muscle tone-increased exercise syndrome. Parkinson's disease and Parkinson's syndrome belong to the extrapyramidal disease manifested by hypertonic-hypokinetic syndrome.

Extrapyramidal response

Extrapyramidal reaction one, cortical striatum pathway

Fibers from the cerebral cortex (mainly from the frontal and parietal lobes) to the striatum, which emits fibers to the red nucleus of the midbrain, substantia nigra, etc. The substantia nigra emits fibers to the pontine, reticular reticular network, and finally Reach the motor neurons in the anterior horn of the spinal cord.

Extrapyramidal response 2, cortex, pontine, cerebellar pathway

Fibers from each cerebral cortex (frontal, temporal, and occipital lobe) to the pontine nucleus, after the replacement, the fibers cross to the contralateral side, stop at the cerebellar cortex via the pontine arm, and then emit fibers from the cerebellar cortex through the dentate nucleus Deep nucleus of the cerebellum), the red nucleus descends to motor neurons in the anterior horn of the spinal cord.

Extrapyramidal response

In the process of controlling the body's movement, the cerebral cortex has to continuously receive feedback information from the lower-level center, and often adjust its outgoing impulses, so that the body can have appropriate muscle tension, maintain a certain posture and posture, and at the same time allow free movement in strength and direction To achieve the desired effect. Among these connections, the perfection of brain, cerebellar circuits, striatum, and cerebellar function plays an important role.

The main functions of the cerebellum are to maintain body balance, regulate muscle tone, and coordinate movement. The cerebellar hemisphere has a bidirectional connection with the cerebral cortex, that is, the cerebellum is controlled by the descending cerebral cortex on the one hand, and it also sends out fibers to return to the cerebral cortex. The efferent fibers of the cerebellum are mainly from the dentate nucleus, some of which stop at the red nucleus and reach the anterior horn of the spinal cord through the red nucleus spinal cord bundle; while most of the fibers stop at the thalamus, which sends out fibers that return to the cerebral cortex and initiate the Free movement plays a regulating role. This large and small cerebellar cortex loop is the most developed in humans. In patients with cerebellar injury, the strength, direction, speed, and range of voluntary movements are not well controlled, and they are manifested as weakness, lack of balance, and lack of coordination. That is, the limbs are weak, and the walking is unstable; when the patient closes his eyes, both feet and disturbs standing, he cannot maintain his own balance; the coordination movement also has obstacles. When the antagonist muscles perform rotation movements, the coordination obstacle is obvious, which is called Disorder of intentional coordination, also known as cerebellar ataxia.

The function of the striatum is not completely clear. The clinical manifestations of pathological injuries in this system are divided into two major categories: one is a syndrome with too much exercise and muscle tension, such as chorea and hand-foot twitch disease; the other is with too little exercise and muscle tension Strong syndromes, such as tremor paralysis (Parkinson's disease).

Extrapyramidal reaction

Drug-induced extrapyramidal reactions are particularly common in the clinic. There are a variety of commonly used drugs that have side effects that cause extrapyramidal reactions, such as phenagen, cefecrine, atropine, metoclopramide, metronidazole, cimetidine, chlorpromazine, and perphenazine. These drugs can produce extrapyramidal excitement to a certain extent, and can cause the central nervous system to control the extrapyramidal system imbalance, resulting in increased excitability of the extravertebral system, resulting in muscle strength and tension controlled by the extrapyramidal system. Degree of loss of control, causing a series of symptoms and signs related to muscle strength and tension. Drug-derived extrapyramidal reactions can be effectively prevented. The key is to follow the doctor's advice, do not easily increase the dosage, and do not buy drugs at will. If abnormalities occur, contact your doctor in time.

Chlorpromazine can also block dopaminergic neural pathways in other parts of the brain, and it can also block the and M receptors of the autonomic nervous system, which is mainly related to causing some adverse reactions. For example, blocking the D2 receptor of the nigro-striatal pathway weakens the DA function in the striatum and enhances the function of Ach to cause extrapyramidal reactions, including Parkinsonism and acute dystonia. Dystonia) and akathisia can be reduced or relieved with central anticholinergics. Another type of vertebral extracorporeal reaction, tardle dyskinesia, may be related to the long-term up-regulation of dopamine receptors. Anti-DA drugs can reduce this response.

Drugs that cause extravertebral responses in the extrapyramidal response

Extrapyramidal response antipsychotic

Chlorpromazine, triflurazine, fluphenazine, haloperidol, perphenazine, lithium carbonate, tricyclic antidepressants, etc. In general, the incidence of extrapyramidal reactions caused by this class of drugs is the highest, and it is related to the dose, course of treatment and individual.

Extrapyramidal reaction

It is related to the dosage and time of medication. If the dosage is controlled below 30mg per day, the incidence can be significantly reduced in short-term use.