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Dangling hand: causes, symptoms, diagnosis
Last reviewed: 06.07.2025

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In neurological practice, sometimes we encounter patients with wrist drop syndrome, in whom tendon reflexes on the hands are evoked (they are not reduced), and their possible increase seems doubtful. The absence of demonstrable sensory disturbances makes it difficult to interpret such a clinical picture. Wrist drop is a symptom similar to foot drop. The first thing that should be established in such cases is whether the weakness of wrist extension has a peripheral or central origin.
There are two causes of wrist drop syndrome:
- Peripheral origin (damage to the radial nerve, n. radialis).
- Central origin (lacunar infarction or occlusion of the peripheral branch (a. rolandica) of the middle cerebral artery).
Drooping brush of peripheral origin
A simple and effective way to differentiate these two conditions is to ask the patient to pick up a stick, which the doctor holds horizontally in front of the patient (Wartenberg test). Normally, this movement involves simultaneous contraction of not only the muscles of the hand, but also the long extensors and flexors of the forearm.
In case of damage to the radial nerve, the drooping of the hand during this test becomes even more pronounced, i.e. the test leads to the maximum drooping of the hand and reveals the impossibility of performing this task. In case of central damage, there will be a slight lifting of the hand and some movement in the adjacent joints, such as bending at the elbow.
In addition, a drooping wrist due to damage to the radial nerve is accompanied by weakness of the finger extensors. The muscle Extensor digitorum longus acts on the carpometacarpal joint of each of the 2nd to 5th fingers. When the doctor places his index finger under the main phalanges of these fingers of the patient, he supports them, compensating for the dysfunction of the radial nerve, and it becomes possible to extend the fingers at the interphalangeal joints, since this function is provided by the ulnar nerve.
It can be quite useful to evaluate the two reflexes that the radial nerve is involved in. With a high radial nerve lesion on the arm, the triceps reflex and biceps stretch reflex will be reduced or absent. If the lesion is directly above the elbow, the triceps reflex may be normal and only the biceps stretch reflex will be reduced.
There is one location of damage to the radial nerve in which both reflexes remain intact. This is on the forearm, just below the elbow joint, within the supinator muscle.
With a central hanging wrist, reflexes will, of course, be higher on the affected side.
Finally, the examination of cutaneous sensory function yields characteristic results. The innervation area of the radial nerve is the dorsal surface of the thumb and index finger and the dorsal surface of the hand immediately between them. Only in the case of long supinator syndrome will there be no sensory deficit, but this condition is recognized by the motor symptoms as indicated above.
With central drooping wrist, skin sensitivity is not impaired or there is numbness of the entire arm.
In most cases, measuring nerve conduction velocity provides us with an answer to the question of whether the lesion is peripheral or central, and if peripheral, where exactly it is located. But EMG is not always available, and clinical analysis can resolve this issue.
Once the peripheral nature of the lesion has been established, the next task is to determine whether the radial nerve lesion is isolated or just part of a widespread disease of the peripheral nervous system, in other words, polyneuropathy. Except in cases of unambiguous situations, such as wrist drop due to a humeral fracture or surgical treatment, including a plaster cast, it is necessary to check the function of other peripheral nerves of all four limbs. The fact is that sometimes radial nerve lesion can be the debut of polyneuropathy, which from a "silent" phase passes into wrist drop. A well-known example is lead polyneuropathy. Dysfunction of the radial nerve can also be the first symptom of periarteritis nodosa, 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 isolated peripheral wrist drop. The most well-known is "Saturday night palsy" caused by the upraised arm being compressed by the back of a park bench when the person is so intoxicated that the warning tingling sensations that necessarily precede all compression palsies are not felt. Romantically known as "groom's palsy" or in French "paralysie des amants", it results from the pressure exerted by the sleeping partner's head on the abducted upper limb. Compression of the radial nerve at the most distal level (distal forearm, wrist and hand) is easily recognized by the accompanying pain and paresthesias ("prisoner's palsy", Wartenberg's disease).
Drooping brush of central origin
Central floppy wrist is almost exclusively of vascular etiology, due to occlusion of a small vessel, most often in the peripheral or subcortical distribution of the branches of the middle cerebral artery. The lesions found are called lacunae and the type of stroke is called lacunar stroke. It is a consequence of hypertensive arteriopathy, and neuroimaging often reveals an arteriopathic pattern in the form of other lacunae that are asymptomatic at the moment, or diffuse areas of decreased density in the white matter of the cerebral hemispheres and/or the surrounding anterior and posterior horns of the lateral ventricles. This picture is characteristic of Binswanger's subcortical arteriosclerotic encephalopathy. MRI is the main diagnostic tool in such cases.
The Wartenberg test described above helps diagnose wrist drop of central origin. In addition, it sometimes reveals a tendency for the entire wrist to be weak, rather than just the muscles innervated by one nerve.