A 31-year-old woman presented to the emergency department with complaints of neck pain and unilateral headache that developed 3 days prior. The patient reported that her headache felt severe, pulsating and throbbing in intensity and quality, and it was primarily felt on the right side of her head. She also felt nausea. The patient had no recent travel history or trauma; however, she visited her chiropractor for spinal manipulation several days prior. On physical examination, nystagmus, ataxia, and extremity weakness was seen.
What’s the diagnosis?