Final answer:
A lesion at the T5 level on one side of the dorsal column will lead to hemiplegia and loss of fine touch and proprioceptive sensations on the lesioned side. Pain and temperature sensations are lost on the opposite side due to the crossing of the spinothalamic pathway. Such sensory discrepancies help localize the level of spinal cord damage, which can be assessed with clinical testing or imaging technologies.
Step-by-step explanation:
When a lesion occurs at the dorsal column of the spinal cord on one side at the T5 level, it can lead to a condition known as Brown-Séquard syndrome. This condition is characterized by hemiplegia on the side of the lesion where the injury occurs, meaning that the leg on the same side as the lesion will be paralyzed. Sensory processing below the level of the lesion is affected in a distinct pattern. On the side with the dorsal column lesion, there will be a loss of fine touch and proprioceptive sensations, yet painful stimuli may be acknowledged due to the intact spinothalamic tract which decussates (crosses) and ascends contralaterally.
The dorsal column system, comprising the fasciculus gracilis and the fasciculus cuneatus, is responsible for carrying information regarding fine touch, vibration, and proprioception. Below the level of a hemisection, sensory discrimination can be used to pinpoint the level of damage because above the lesion, normal function remains. Imaging technologies like MRI or CT scanning can also localize the injury, but simple clinical testing with a cotton-tipped applicator can be immediately valuable on the scene of an accident.
On the non-lesioned side, the situation is different. The patient, while maintaining motor function, will lose the ability to feel pain and temperature stimuli due to damage of the ascending fibers in the spinothalamic pathway that have already crossed over at the point of the hemisection. This discrepancy in sensory abilities between the two sides helps to identify and localize the spinal damage.