A 72-year-old woman from Bangalore with hypertension and diabetes presents with acute onset vertigo, ataxia, and left-sided facial numbness of 4 hours duration. Vital signs: BP 158/92 mmHg, HR 92/min. Non-contrast CT head is unremarkable. MRI brain with DWI/ADC and MR angiography (MRA) shows a small acute DWI hyperintense lesion in the left cerebellar hemisphere with normal flow signal in the vertebral and basilar arteries. What is the most likely diagnosis?