Final answer:
The question addresses the sensory deficits expected after a hemisection in the thoracic region of the spinal cord, resulting from a motorcycle accident. Pain stimuli would be perceived on the damaged side without fine touch, while the reverse is true for the other side.
Step-by-step explanation:
Sensory Deficits after Spinal Cord Injury
Following a motorcycle accident, where the victim has lost the ability to move the right leg but retains control over the left leg, there is an indication of a hemisection in the thoracic region of the spinal cord. In terms of sensory deficits, this could mean that below the level of the hemisection, pain stimuli would be perceived on the damaged side, but not fine touch. Conversely, the opposite would hold true for the other side where fine touch is intact but pain perception is lost due to the crossing over of pain fibers in the spinal cord.
This kind of damage affects the pathways responsible for carrying sensory information to the brain. The spinothalamic tract, which carries pain and temperature signals, decussates, or crosses the midline, shortly after entering the spinal cord. This means that damage to one side of the spinal cord will affect the ability to perceive pain and temperature on the opposite side of the body below the level of injury. The dorsal columns, which carry fine touch and proprioceptive information, do not cross over until they reach the medulla in the brain. Therefore, damage to these tracts will affect sensation on the same side of the body where the injury occurred.
Sensory tests can assess for such damage using submodalities such as touch, temperature, vibration, pain, and proprioception. Results from these tests provide valuable insights into the specific location and extent of the injury. If such an injury occurs, it may lead to paralysis or loss of sensation and movement in the affected area of the body.