Final answer:
Individuals with C-8 spinal cord injuries are tetraplegic but have some voluntary control over their hands. Hemisection of the spinal cord leads to hemiplegia, where the damaged side's leg is paralyzed. Sensory deficits vary because different pathways are affected differently; fine touch is lost while pain sensation is preserved.
Step-by-step explanation:
Individuals with spinal cord injuries ranging from C-5 to C-8 are considered tetraplegic, meaning they experience paralysis in all four limbs. However, those with lesions at C-8 have voluntary control over certain muscles. Typically, they maintain some hand movement, which is enabled because the lower cervical spinal cord (including C-8) has wider ventral horns in the ventral horn, reflecting the more significant number of arm and hand muscles controlled by these motor neurons. The cervical enlargement accommodates the need for greater control over the fine musculature of the upper limbs, particularly the fingers.
A hemisection of the spinal cord, which might occur in events like a motorcycle accident, impacts only one side of the spinal cord. This type of injury can lead to hemiplegia, where one leg is paralyzed due to damage on the same side as the trauma, affecting the lateral corticospinal tract. Sensory deficits after hemisection are complex because the dorsal column pathway, responsible for fine touch and proprioceptive sensations, ascends ipsilaterally and therefore would be damaged. However, the spinothalamic pathway, which carries pain and temperature information, decussates right after entering the spinal cord and ascends contralaterally, resulting in the patient's ability to acknowledge painful stimuli on the paralyzed leg but not fine touch or proprioception.