A 67 years old man presents with rapid onset of right-sided weakness and a subjective feeling of decreased sensation on his right side. His family reported that he seemed to have difficulty forming sentences. Symptoms were maximal within a minute and began to spontaneously abate 5 minutes later. On arrival, 30 minutes after onset, his clinical deficits had largely resolved with the exception of a subtle weakness of his right hand. His history is significant for hypertension, diabetes, hyperlipidemia, and a 50 pack-year smoking habit. What is the most likely diagnosis?