Perhaps one of the most famous reflexes for all people is the metacarpal beam, also called carporadial. It can be called by striking with a special hammer on the process of the beam. And the carporadial reflex is manifested in the flexion of the elbow joint, as well as pronation (turning inward) of the fingers.
General information
It’s worth starting with the definition. Carporadial reflex refers to the deep. What does it mean? Reflexes of the deep type are called involuntary muscle contractions, acting as a response to the stimulus.
How is this process going? Muscles involuntarily contract, tendons are stretched at this moment. Often, this type of reaction is determined at the time of a short jerking strike at the place where the tendons are attached to the muscles.
It is very important that the patient is relaxed. It is necessary to get rid of stiffness, tension. Muscle tissue should be absolutely relaxed. Otherwise, it will be simply impossible to determine the degree and presence of any reflex (carporadial - all the more). Why? Because at the moment of tension the muscles are pulled. Because of this, reflexes either disappear or become inaccurate.
How is reflex determined?
To do this, you need a special device - a neurological hammer. With its help, an initial examination is carried out for the presence of violations and reflexes.
A mallet intended for percussion (tapping) is indispensable for a neurologist. Of course, it differs radically from the usual one. This is a special device for the primary detection of neurological disorders. Hammers are made exclusively of metal, equipped with rubber pads, and also with a brush and a needle to check the sensitivity of individual parts of the body.
After the test, this device determines the depth of the carporadial reflex. The following degrees exist:
- 0 points. The reflex is completely absent.
- 1 point The reaction is very low.
- 2 points. There is a reaction, and it is normal.
- 3 points. There is a very lively reaction, with normal severity.
- 4 points. The reaction is maximized.
Of course, the severity may vary. Interestingly, in the lower extremities, tendon reflexes are manifested much more clearly (and are caused easier) than in the case of the hands.
Reflex
Now we should discuss this topic. The carporadial reflex is caused by striking the styloid process of the radius. The correct reaction to this action is flexion of the limb in the elbow joint, as well as pronation and flexion of the fingers.
The most important thing in reflex research is to bend a limb at a slight obtuse angle. Also, the patient must hold the hand in weight with his free hand. The position is average - between supination and pronation.
Reflex arc
So in medicine is called the path that the nerve impulses pass during the implementation of a particular reflex. In this case, it looks like this:
- Pronators (mm. Pronatores).
- Superficial flexor (flexor digitorum).
- Brachioradialis (brachio-radialis) and biceps.
- The median nerve (nn. Medianus).
- The radial nerve (radialis).
- Musculoskeletal nerve (musculo-cutaneus).
- Cervical segments of the spinal cord. Involved V, VI, VII and VIII.
Such a path passes a nerve impulse at the time of manifestation of the carporadial reflex.
The role of the spinal cord
He is directly involved in the implementation of the tendon reflex. In a reflex arc, the cervical segments of the spinal cord are the endpoint of transmission of a nerve impulse.
Interestingly, almost all of them have collateral branches. They are sensitive and directly in contact with peripheral motor neurons. Those, in turn, are located in the front horns.
Collaterals not only reach motor neurons, they also penetrate into its neighboring segments. As a result, spinal-spinal intersegmental bonds are formed, which provide for irradiation of excitation. As you might guess, it enters the spinal cord after the receptors of superficial and deep sensitivity located on the periphery are irritated.
This is precisely due to the widespread motor-reflex reaction, which is a response to local irritation.
Reaction features
The carporadial reflex is carried out due to a blow to a very specific area of the hand with a hammer - along the process of the beam. There is another similar view, and this is a flexion-elbow reaction. You can call it by hitting the area of the phalanx of the thumb. It must be placed on the elbow bend and press on the area where the tendon is localized by the 2-headed muscle.
At this point, the patient’s hand should be bent, and the forearm should be relaxed, always lying on the surface of the thigh. Visually reflex tests may seem similar, but in this case, the reaction is only bending the arm in the elbow joint.
Hyperreflexia
Within the framework of the topic under discussion, it will be appropriate to study violations. And you can start with a story about an increased tendon reflex.
This is also called hyperreflexia. What is the reason for this violation? In fact, it consists in enhanced reflex activity of the segmental apparatus. It, as mentioned earlier, includes the brain stem and spinal cord.
Usually this pathology indicates the presence of a disease in a person. The most common causes of hyperreflexia include the following conditions:
- Viral transverse myelitis.
- Spinal cord lesions.
- Vegetative disorders.
- Diseases of Machado Joseph.
- St. Louis Encephalitis Virus.
- Spinal cord infarction.
- Hepatic encephalopathy.
- Creutzfeldt-Jakob disease.
- Eclampsia.
- Preeclampsia
- Insomnia.
- Multiple sclerosis.
- AIDS dementia syndrome.
- Rocky Mountain Spotted Fever.
Hyperreflexia can also develop due to a bite by a Latrodectus spider (Black Widow), due to poisoning by psychostimulants or as a result of the influence of tetanotoxin.
Hyporeflexia
A similar phenomenon also needs to be addressed. It was described above about the increased tendon reflex, now it is worth discussing cases when the person's discussed reactions are slowed down.
What are the reasons? Decreased tendon reflexes occur due to damage to peripheral neurons. But not always. Hyporeflexia is observed in such cases:
- As a variant of the norm. In some healthy people, deep reflexes are weakened, but this does not affect their health.
- Delay relaxation. Pretty rare case. Pathology is characteristic of hypothyroidism. If it is observed in a patient, it is possible that his thyroid function is impaired.
- Spinal shock. Quite a common cause of areflexia. It is observed in the early stages of spinal cord injury. The cause is usually a vascular lesion, trauma, or swelling.
- Stroke in the acute stage. In this case, hyporeflexia is replaced by hyperreflection over time.
- Myopathy.
In some patients, asymptomatic areflexia occurs. Pathology is combined with the expansion of the pupil and the lack of its reaction to light. Also, medicine knows cases of isolated one-sided loss of one of the reflexes.
Areflexia
This phenomenon deserves special attention. It consists in the absence of tendon reflexes. The reason is a violation of the integrity of the reflex arc. Areflexia can also occur due to the inhibitory effect exerted by the higher parts of the nervous system. This, in turn, usually provokes either a serious illness or trauma.
The absence of reflexes is a valuable diagnostic feature that gives the neurologist the opportunity to assess how badly the nervous system is affected.
An example should be given. If a person does not have reflexes of the lower extremities, but the upper ones are not broken in any way, then most likely he has a spinal cord in the chest or lumbar region.
However, in some cases there is a total absence of reflexes. Then we can talk about the inhibition of the central nervous system. For example, with anesthesia and coma, most reflex arcs do not react to anything. And the deeper one of these conditions is, the more pronounced is the depression of the central nervous system.