Final answer:
Loss of sensation in a single dermatome can be due to damage to a spinal nerve or a spinal cord region such as a hemisection. Imaging like MRI or CT scans can localize such injuries, but simple tools can also be useful in an immediate assessment.
Step-by-step explanation:
Loss of sensation in a single dermatome on one side of the body could indicate damage to a spinal nerve or potentially to the corresponding region of the spinal cord, including a spinal cord hemisection. Each dermatome is a specific area of skin that is innervated by sensory fibers from a single spinal nerve. Damage or trauma, such as that from a motorcycle accident, can cause a hemisection or other injuries to the spinal cord, leading to paralysis, changes in sensation, or other motor function issues below the injury site.
Imaging technology, such as magnetic resonance imaging (MRI) or computed tomography (CT) scans, can help localize the injury. However, sometimes, simple tools like a cotton-tipped applicator are used to detect loss of sensation and more accurately determine the level of damage, especially in urgent, on-scene evaluations.