Background New migraine–like TNAs in older adults can be due to migraine aura or TIA. Clinical distinction can be difficult after a first attack, particularly in older patients with vascular risk factors. In the absence of previous prospective population–based studies, we determined the long–term risk of stroke in patients with new migraine–like TNAs, defined pragmatically as those in whom the assessing neurologist was unable to say confidently that the event was a definite aura or a definite TIA.

Methods As part of a population–based study of all TNAs, TIAs and strokes (Oxford Vascular Study; 2002–2012), we ascertained all patients with a first migraine–like TNA in whom the study neurologist was not confident that the event was either a definite migraine aura or a definite TIA. Risk of stroke was determined by long–term regular face–to–face follow–up and was compared with the rate expected on the basis of age–sex specific stroke incidence in the underlying study population and with the rate observed in study patients with definite TIA.

Results 158 consecutive patients with eligible migraine–like TNAs (97 women and 61 men; median age= 61.3 years) had 776 patient–years of follow–up. The 90–day risk of stroke (n=2, 1.26%) was lower than that expected after a definite TIA (age and sex–adjusted HR=0.23, 0.07–0.89). The subsequent risk of stroke (n=8; 1.1/100 patient–years) was non–significantly greater than expected based on background population incidence (n=2.73; 0.37/100 patient–years), but remained lower than that after definite TIA (HR=0.58, 0.36–0.84). Nine of the 10 strokes on follow–up were ischaemic and 3 were in the posterior circulation.

Conclusions The short and long–term risks of stroke in patients with a first migraine–like TNA are significantly lower than after a definite TIA. The trend towards a higher stroke risk than the underlying population rate is similar to that seen in studies of individuals with clinically–definite migraine with aura.