Hanging brush: causes, symptoms, diagnosis

In neurological practice, patients with a hanging hand syndrome are sometimes found who have tendon reflexes on their hands (they are not lowered), and their possible increase looks questionable. The absence of evidence-based sensitive disorders makes interpretation of such a clinical picture difficult. A hanging brush is a symptom similar to a hanging stop. The first thing that should be established in such cases is whether the weakness of the extension of the hand has a peripheral or central origin.

[1], [2], [3], [4], [5]

There are two reasons for the syndrome of the hanging brush:

1. Peripheral origin (damage to the radial nerve, n. Radialis).
2. Central origin (lacunar infarction or occlusion of the peripheral branch (a. Rolandica) of the middle cerebral artery).

Hanging brush of peripheral origin

A simple and effective way to dilute these two conditions is to ask the patient to take a stick that the doctor holds horizontally in front of the patient (Wartenberg test). In normal with this movement there is a simultaneous contraction of not only the muscles of the hand, but also the long extensors and flexors of the forearm.

In the case of damage to the radial nerve, the dangling of the hand during this test becomes even more pronounced, that is, the sample leads to the maximum dangling of the brush and reveals the impossibility of performing this task. In the case of central lesion, there will be a slight uplift of the hand and some movement in the adjacent joints, such as flexion at the elbow.

In addition, the dangling brush due to the defeat of the radial nerve is accompanied by the weakness of the extensor fingers. The muscle The long extensor of the fingers acts on the wrist-metacarpal joint of each of 2-5 fingers. The doctor, when installing his index finger under the main phalanges of these fingers of the patient, supports them, compensating for the dysfunction of the radial nerve, and it becomes possible to extend the fingers in the interphalangeal joints, since this function is provided by the ulnar nerve.

It is quite useful to evaluate two reflexes, in which the radial nerve is involved. With a high lesion of the radial nerve on the arm, the triceps reflex and bicep reflex of the stretch will be reduced or absent. If the lesion level is directly above the elbow, then the triceps reflex can be normal and only the bicep reflex stretching will be lowered.

There is one localization of damage to the radial nerve, in which both reflexes remain undisturbed. This is on the forearm, directly under the elbow joint, within the muscle of the instep.

With a central hanging brush, the reflexes, of course, will be higher on the side of the lesion.

Finally, the study of the function of skin sensitivity gives characteristic results. The area of innervation of the radial nerve is the dorsal surface of the large and index fingers and the back surface of the brush directly between them. Only in the case of the syndrome of the long instinctor there will be no sensitive deficiency, but this condition is recognized by motor symptoms, as indicated above.

With a central hanging brush, skin sensitivity is not impaired or there is numbness in the entire arm.

In most cases, measuring the speed of conduction along the nerve provides us with the answer to the question whether the damage is peripheral or central, and if peripheral, then where exactly it is located. But EMG is not always available, and clinical analysis allows to solve this problem.

When the peripheral nature of the lesion is established, the next task is to determine whether the damage to the radial nerve is isolated or only part of the widespread disease of the peripheral nervous system, in other words, polyneuropathy. In addition to cases of unambiguous situations, such as a hanging brush due to a fracture of the humerus or surgical treatment, including a plaster bandage, it is necessary to check the function of the other peripheral nerves of all four limbs. The fact is that sometimes the defeat of the radial nerve can be the debut of polyneuropathy, which from the "silent" phase turns into a dangling brush. A well-known example is lead polyneuropathy. Radiation nerve dysfunction may also be the first symptom of nodular periarteritis, which affects the vasa nervorum of all peripheral nerves. And, of course, diabetic metabolic disorders are a predisposition to compression neuropathy.

Compression neuropathy is the most common cause of an isolated peripheral hanging brush. The most famous is the "paralysis of the Saturday night" due to the squeezing of the raised hand with the back of the park bench, when the person is in a state of such strong intoxication that the warning tingling sensations that necessarily precede any compression paralysis are not felt. The romantic name "paralysis of the groom" or in French "paralysie des amants", arises from the pressure exerted by the head of the sleeping partner on the withdrawn upper limb. The compression of the radial nerve at the very distal level (distal forearm, wrist and hand) is easily recognized by concomitant pain and paresthesia ("parental convulsion", Wartenberg's disease).

Hanging brush of central origin

The central hanging brush is almost exclusively a vascular etiology, due to the occlusion of a small vessel most likely in the peripheral or subcortical distribution of the branches of the middle cerebral artery. Detected lesions are called lacunae and the type of stroke - lacunar stroke. This is a consequence of hypertensive arteriopathy, and neuroimaging often reveals an arteriopathic pattern in the form of detection of other lacunae that are asymptomatic at the moment, or diffuse areas of reduced density in the white matter of the brain hemispheres and / or surroundings of the anterior and posterior horn of the lateral ventricles. This picture is typical for subcortical arteriosclerotic encephalopathy Binswanger. MRI in such cases is the main diagnostic tool.

The Wartenberg test, described above, helps diagnose a hanging brush of central origin. In addition, sometimes the tendency to weakness of the whole brush is revealed, and not only the muscles innervated by one nerve.