Erb’s palsy is a condition that impacts arm movement and sensation, resulting from an injury to the brachial plexus, a network of nerves near the neck. This nerve network is responsible for controlling the muscles and feeling in the shoulder, arm, and hand. When these nerves are stretched or otherwise damaged, it can lead to weakness or a lack of movement in the affected limb.
Characteristic Arm and Hand Positions
A common visual indicator of Erb’s palsy is a distinct posture known as the “waiter’s tip” position. The affected arm hangs by the side, rotated inward towards the body. The elbow remains extended, and the forearm is turned so the palm faces backward or outward, with the wrist often flexed and fingers curled or extended. This characteristic positioning occurs due to weakness or paralysis of specific muscles that normally control outward rotation of the shoulder, bending of the elbow, and supination of the forearm. The shoulder on the affected side may also appear visibly dropped or rotated compared to the unaffected side.
Noticeable Limitations in Movement
Erb’s palsy presents with clear limitations in an individual’s ability to move the affected arm. There is often a noticeable inability to raise the arm away from the body or above the shoulder. Bending the elbow can be difficult or impossible, and rotation of the arm, especially outward rotation, is significantly restricted. For infants, a prominent sign is the lack of spontaneous movement in the affected arm, which may appear limp or floppy compared to the active movements of the unaffected arm. This asymmetry in arm use is a key visual cue, as the child may favor their unaffected limb for reaching and grasping.
Subtle and Varying Presentations
The visual presentation of Erb’s palsy can vary considerably among individuals, ranging from subtle signs to more pronounced differences. In milder cases, the affected arm might exhibit only slight weakness or less fluid movement, with the characteristic postures being less obvious. Conversely, in more severe instances, the arm may appear completely limp, a condition known as flaccid paralysis, with no visible voluntary movement. The extent to which the condition is noticeable can also depend on the specific actions an individual attempts to perform, with limitations becoming more apparent during tasks requiring full arm mobility. It is important to note that Erb’s palsy typically affects only one arm, with involvement of both arms being rare.