Final answer:
The most likely involved dermatome for loss of sensation to the right heel is S1. In terms of a hemisection of the thoracic spinal cord, sensory deficits would include a loss of fine touch and proprioception on the right side, and a loss of pain and temperature sensation on the left side of the body below the level of the lesion.
Step-by-step explanation:
If a man has lost sensation to his right heel, the dermatome most likely involved would be S1 (first sacral nerve). The dermatomes are specific areas of skin that are innervated by a single spinal nerve root. The S1 dermatome covers the outer part of the foot and the heel, so damage to the S1 nerve could result in loss of sensation in the heel area.
Sensory deficits after a spinal cord hemisection can be complex. With a hemisection in the thoracic region of the spinal cord, a patient would likely have sensory deficits with variations in the perception of touch versus pain. This occurs because different sensory pathways in the spinal cord handle different types of sensations and have different points of decussation (crossing over). For instance, the dorsal column pathway, which carries sensations of fine touch and proprioception, does not decussate until it reaches the medulla oblongata in the brainstem. Therefore, a lesion or damage on the right side of the spinal cord would affect the right-sided dorsal column pathways, leading to a loss of fine touch and proprioceptive sensations on the same side of the body.
In contrast, the spinothalamic pathway, which carries pain and temperature information, decussates soon after entering the spinal cord and ascends on the opposite side. As such, following a hemisection, pain and temperature sensations would be lost on the side opposite the lesion. Thus, a patient with a right thoracic hemisection would have a loss of fine touch and proprioception on the right side and a loss of pain and temperature sensation on the left side below the level of the lesion.