A 58-year-old male presents with slurred speech for half a day and right-sided limb movement difficulty for 8 hours. Examination shows motor aphasia, right-sided central facial and tongue palsy, right-sided limb paralysis, and right-sided sensory deficit. Emergency head CT shows no abnormalities. [Hypothetical scenario] If the condition progressively worsens with impaired consciousness, left pupil dilation, and sluggish pupillary light reflex, the most urgent intervention required is: