In an exam position with the arm placed over a chair, which sensory deficit is most likely observed?

In an exam position with the arm placed over a chair, which sensory deficit is most likely observed?

• A. Decreased sensation lateral
• B. Decreased sensation medial
• C. Decreased sensation posterior
• D. Decreased sensation anterior

Answer: (A)

Placing the arm over a chair stretches the upper part of the brachial plexus, especially the C5–C6 fibers. Injury to this region produces an Erb-type pattern, with sensory loss most evident over the lateral aspect of the proximal arm near the shoulder (the lateral upper arm/shoulder region). So the lateral surface is the area most likely to have decreased sensation in this position. The other regions described (medial, posterior, anterior) involve different nerves and dermatomes not primarily affected by this upper-plexus traction pattern.

Placing the arm over a chair stretches the upper part of the brachial plexus, especially the C5–C6 fibers. Injury to this region produces an Erb-type pattern, with sensory loss most evident over the lateral aspect of the proximal arm near the shoulder (the lateral upper arm/shoulder region). So the lateral surface is the area most likely to have decreased sensation in this position.

The other regions described (medial, posterior, anterior) involve different nerves and dermatomes not primarily affected by this upper-plexus traction pattern.