A 35-year-old right-handed male chef reported three similar neurological episodes in the preceding 6 months. Each episode began with a paroxysm of sneezing. In the first, sneezing was followed by sudden onset dizziness, and then over a few minutes by double vision, left-sided paraesthesiae, left-sided weakness and then a severe left-sided headache, all resolving after a few hours. The second and third episodes, approximately 2 months apart, were less severe. During the second event, he also noticed his right pupil was bigger than the left. In the third episode, 6 weeks before his clinic visit, he developed several hours of ataxia and double vision, but no sensory or motor symptoms; this was followed by left-sided headache.

The patient underwent MRI brain and magnetic resonance angiography (MRA) of the cervical vessels (figure 1).