Final answer:
To test for the T4 dermatome, a sensory exam using a cotton-tipped applicator should be conducted around the chest region, specifically at the level of the nipples, to assess touch perception and sensory differences.
Step-by-step explanation:
To test for the T4 dermatome, one would perform a sensory exam involving the light touch of the soft end of a cotton-tipped applicator on the skin. Since the T4 dermatome corresponds to the sensory innervation of the skin by the fourth thoracic spinal nerve, the test should be conducted in the chest region, more specifically around the level of the nipples. This process is intended to evaluate if the touch is perceptible and if there are any differences in sensations across this specific dermatomal area.
It is essential to assess sensory perception in a systematic manner, testing from distal to proximal locations on the limbs, or from lateral to medial on the trunk. As the T4 dermatome covers the area of the chest, the sensory exam would include a comparison of perception between the left and right sides of the torso as well as sensory testing above and below the level of the T4 dermatome to ensure accurate localization of sensory deficits or alterations.