Elderly individuals are particularly at risk for intracranial bleeding primarily due to which of the following factors?

Elderly individuals are particularly at risk for intracranial bleeding due to the enlargement of the subdural space. As people age, the brain undergoes atrophy, meaning it shrinks in size. This change in brain structure can lead to an expansion of the subdural space, which is the area between the brain and the outer layer of the protective membranes covering the brain (the dura mater).

When there is an increase in the subdural space, the brain is less securely anchored, making it more susceptible to injury from trauma, even minor falls that might not cause an injury in a younger individual. Additionally, the bridging veins in this area become more vulnerable to tearing, which can result in subdural hematomas. These factors combined increase the likelihood of intracranial bleeding in the elderly population.

Other factors mentioned in the options do not directly contribute to the risk of intracranial bleeding in the same way. For instance, depletion of cerebrospinal fluid, constriction of cerebral vessels, and marked increases in brain size do not play a significant role in the increased susceptibility to intracranial bleeding like the enlargement of the subdural space does.