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Elbow wrist syndrome
Last reviewed: 04.07.2025
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Elbow syndrome of the wrist (lesion in the Guyon canal) is characterized by paresthesias on the inner surface of the hand, sometimes with irradiation to the forearm, hypoesthesia only on the palmar surface of the fifth finger. Weakness of flexion and adduction of the fifth finger, adduction of the first finger is revealed.
Tests that provoke painful sensations (finger pressure, tapping, cuff) are of diagnostic value.
Electrophysiological methods of examination have a special diagnostic value. Stimulation of the ulnar nerve can be performed transcutaneously, using surface electrodes or needles inserted into the muscle. To study the motor latent period and the speed of impulse conduction along the ulnar nerve, electrodes are applied or inserted into the area of the muscle that abducts the little finger.
The surface active recording electrode can be applied to the middle of the thenar. This electrode placement allows for the recording of muscle potentials during stimulation of not only the ulnar but also the median nerve.
To study the conduction of impulses along the ulnar nerve at all possible levels of its compression, it is necessary to stimulate the nerve at four points: in the axillary region, above the elbow, below the elbow, and on the wrist. This technique allows us to study four motor latent periods and three impulse conduction speeds along the ulnar nerve.
Because of the different locations of the points where the ulnar nerve is irritated, the average values of the impulse conduction velocity in individual segments of the nerve vary considerably in groups of healthy individuals. Thus, the impulse conduction velocity along the motor fibers of the ulnar nerve on the shoulder is 65.7 - 53.6 m/s, and in the transulnar segment of the nerve - 57 - 44 m/s. Almost always, a significant decrease in the impulse conduction velocity in the transulnar segment of the nerve is detected compared with the impulse conduction velocity on the shoulder and forearm. If this study is carried out with the elbow joint fully extended, the average impulse conduction velocity in the transulnar segment (49.9 m/s) is 20.2% lower than on the forearm. If the average speed is determined with the upper limb bent at the elbow joint at an angle of 70°, it increases in the transulnar segment of the nerve to 62.7 m/s, becoming comparable with the speed in the forearm.
The normal distal motor latency in the "wrist - abductor muscle of the little finger" region is on average from 2.3 to (3.38 ± 0.005) m/s. This indicator in the "wrist - adductor muscle of the thumb" region is on average 2.8 m/s, and at the distance "above the elbow joint - abductor muscle of the little finger" - (7.9 ± 0.85) m/s. When stimulating the nerve above the elbow joint and recording the muscle potential from the ulnar flexor of the wrist (with an average distance between the stimulating and recording electrodes of 13.5 cm), the motor latency is (3.1 ± 0.3) m/s.
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