Final answer:
The L4 dermatome can be tested by assessing sensory perception around the knee using a light touch with the soft end of a cotton-tipped applicator to verify the proper function of the L4 spinal nerve sensory fibers.
Step-by-step explanation:
To test for the L4 dermatome, you would assess the area around the knee. The L4 spinal nerve dermatome primarily innervates the skin over the knee and extends to the medial surface of the lower leg and foot. Testing the senses begins with examining dermatomes that are connected to specific areas of the skin based on the spinal nerve containing those fibers. To assess sensory function, one might use a light touch with a soft end of a cotton-tipped applicator across different locations within the L4 dermatome. The test examines whether the touch is perceived, indicating the proper function of the L4 spinal nerve sensory fibers.