A 72-year-old man has had 4 episodes of weakness in her right arm and leg...

These are recurrent, brief (10–15 minute), fully resolving focal neurologic deficits, which fits transient ischemic attacks (TIAs) rather than completed stroke. The combination of right-sided arm and leg weakness and difficulty speaking localizes to the left cerebral hemisphere (dominant hemisphere for language in most patients). The additional symptom of transient blurring of vision in the left eye is characteristic of amaurosis fugax, caused by retinal ischemia from emboli or hypoperfusion in the ipsilateral internal carotid circulation. Together, this pattern strongly suggests left internal carotid artery occlusive disease (e.g., high-grade stenosis with artery-to-artery embolization).

Left MCA thrombosis would typically produce persistent deficits rather than multiple short, self-resolving episodes. Intracerebral hemorrhage usually presents with sudden severe symptoms that do not resolve quickly and often includes headache or reduced consciousness. Epilepsy would more likely cause positive symptoms (jerking, automatisms) and postictal confusion. Vertebrobasilar disease causes posterior circulation symptoms (vertigo, diplopia, ataxia), not unilateral monocular vision loss plus contralateral weakness.