Axillary nerve of a person: structure, function and possible diseases

The axillary nerve and the radial are the components of the posterior trunk of the brachial plexus. A nerve passes through the shoulder joint, giving a branch that innervates a small round muscle that rotates the arm outward. Further, the axillary nerve passes behind the lateral humerus before dividing into the posterior and anterior branches that supply a part of the deltoid muscle. To the posterior branch is the cutaneous nerve, which innervates the skin above the lateral surface of the deltoid muscle. Consider in more detail the axillary nerve. His anatomy is unique.

Nerve damage

Most often, axillary nerve damage occurs with a fracture of the humerus or dislocation of the shoulder. In some cases, only the axillary nerve is affected during idiopathic pleksopathy of the brachial plexus . What is the risk of axillary nerve damage? Let's look at this article.

The main clinical manifestation of the compression of the axillary nerve is a violation of the function of shoulder diversion due to weakness of the deltoid muscle. To withdraw the arm begins the supracutaneous muscle, and so the patient can retain a limited ability to withdraw the hand. Although a small round muscle may be weak, it is not always noticeable on a clinical examination as a result of the normal functioning of the subacute muscle.

The diagnosis can be confirmed only by revealing the weakness of the deltoid muscle and the abnormal EMG indices that refer to the small round and deltoid muscles. The SPNV of the axillary nerve when performing superficial records from the muscle (deltoid) serves as a means of detecting a delay in the potential or a decreased amplitude of the MTD of the axillary nerve.

Neuropathy of the upper limb is a fairly common disease in the work of a neurologist. Damage can be as one axillary nerve, and several nerves at once, in connection with which the clinical picture of the disease will differ. Regardless of the reasons that caused the disease, the patient begins to feel pain, loss of sensitivity, a sense of discomfort and other characteristic symptoms.

Causes

Often, patients who have experienced neuropathy of the upper limbs feel that their problems are associated with lack of sleep and fatigue, which can be restored with appropriate rest. Many reasons can lead to polyneuropathy of the hands. The most common are:

• Tumor diseases - and tumors are not necessarily located in the area of the shoulder and armpit. Localization can be any.
• The operations that were carried out earlier (at the surgical site, the blood ceases to circulate normally, and this, in turn, contributes to muscle atrophy and edema formation, including compression of the neural bundles, which leads to neuropathy).
• Long-term use of drugs containing chloroquine and phenytoin - these substances act negatively on nerve fibers.
• Injuries of the limbs with the subsequent development of edema, compressing the nerve - as a consequence, neuropathy arises.
• Various transferred infections, for example, tuberculosis, influenza, diphtheria, HIV, herpes, malaria and others.
• Regular supercooling - the body is very harmful to temperature reduction and prolonged exposure in this state.
• Lack of certain groups of vitamins in the body, often vitamin B.
• Irradiation - affects the body extremely negatively.
• Intoxication of the body.
• Excessive and strong physical exertion on the muscles.
• Endocrine diseases, diabetes mellitus including.

How exactly does the injured axillary nerve manifest?

Symptoms

Symptomatology can be divided into concomitant and basic. At the manifestation of the main symptoms, a person feels burning sensations, which persecute him throughout the day, as well as a feeling of numbness of the fingers, hands in general and a brush. With the concomitant symptomatology:

• Difficulty in moving with your hands;
• Swelling;
• Violations of coordination of movements;
• Involuntary muscle contractions, cramps, spasms;
• Decrease in temperature sensitivity;
• Unpleasant sensations of creepy.

Damaged axillary nerve: diagnosis

To choose the appropriate method of treatment, it is very important to conduct a thorough examination of the patient, make tests, take special tests, evaluate reflexes and muscle strength. Instrumental methods of diagnosis include: magnetic tomography, electroneuromyography.

These methods allow you to detect damage to nerves, to identify the cause and extent of conduction disorders. If necessary, the specialist can direct the patient to conduct additional tests to exclude another pathology. And only after the results can be diagnosed. Very informative Topography of the axillary nerve.

Neuropathy

Neuropathy of the axillary nerve is accompanied by the limitation (inability) of the abduction of the shoulder, its movement back and forth, violation of the sensitivity of the innervation zone, atrophy of the deltoid muscle. Compression of the quadrilateral opening - tunnel syndrome of the axillary nerve (triceps, large and small round muscles, humerus). The pain is localized in the shoulder region and is strengthened by rotation and deflection of the shoulder. Differentiation should be made from discogenic cervical sciatica and periarthritis periarthrosis.

Neuritis

Neuritis is a disease of the peripheral nerve (facial, intercostal, occipital, nerves of the extremities), which has an inflammatory character and manifests itself by pain along the nerve, muscle weakness of the innervated area, a violation of sensitivity. With the defeat of several nerves, the disease is called polyneuritis. The projection of the axillary nerve plays an important role here.

The functions of the nerve, the area of innervation and the degree of lesion determine the clinical picture of neuritis. In most cases, peripheral nerves consist of a different type of nerve fibers: vegetative, sensory, motor. For any type of neuritis, the symptoms are caused by the damage of each type of fiber:

• Trophic and vegetative disorders cause the appearance of trophic ulcers, puffiness, brittle nails, cyanotic skin, dryness and thinning of the skin, depigmentation and local hair loss, sweating and so on;
• Sensitivity disorders cause loss or decrease in the sensitivity of the innervation zone, paresthesia (sensation of chills, tingling), numbness;
• The disturbance of the activity of movements causes the loss or decrease of tendon reflexes, paresis (partial) or paralysis (complete) decrease in the strength of the innervated muscles, atrophy.

First signs

Basically, the first signs of nerve damage are numbness and pain. The clinical picture of some types of neuritis demonstrates specific manifestations that are related to the area that the armpit nerve innervates.

Neuritis of the axillary nerve is expressed in the impossibility of raising the arm to the side, increasing the mobility of the shoulder joint, reduced sensitivity of the upper third of the shoulder, atrophy of the deltoid muscle.

Isolated axillary nerve is affected by injury of the brachial plexus or dislocation of the head of the shoulder. This leads to a fall of the raising of the hand to a horizontal level.

On a small strip of skin on the back of the upper part of the shoulder, sensitivity is impaired. In some cases, the lateral cutaneous nerve of the forearm is injured and the sensitivity is disturbed on the outer-back, radial side of the forearm. All this is the nerves of the axillary region.

To quickly navigate in the defeat of the nerves of the upper extremities, especially the elbow, median and ray, it will be enough to examine the patient for some typical movements of the fingers, hands and forearms. But to begin with it is necessary to be convinced of absence of obstacles of mechanical character to movement because of development of ankylosis or contractures. When the patient will perform the necessary movements, the specialist will need to make sure of the safety of the strength and volume of these movements.

Groups of muscles

The next group of muscles enters the motor innervation of the axillary (axillary) nerve:

Deltoid muscle C5-C6:

• During the reduction of the back, the raised shoulder pulls back.
• During the contraction of the middle part, the shoulder is removed to the horizontal plane.
• During the contraction of the front part, the upward lifted limb pulls forward.

Small round muscle C4-C5, contributing to the rotation of the shoulder outside.

Test

To determine the strength of the deltoid muscle, you can conduct the following test: sitting or standing the patient raises his hand to the horizontal level, and the doctor at this time is resisting this movement, palpating the contracted muscle.

When the axillary nerve is injured, the following occurs:

• Violated sensitivity on the surface of the shoulder (top).
• Paralysis of the axillary nerve, atrophy of the deltoid muscle.

The symptom of the swallowtail is that the extension of the patient's hand is much less than healthy. And if you look at the patient from the side, you get the impression of a split swallowtail and a lag in the extension of the shoulder.