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1042 Evidence of substantial under-recognition of posterior circulation TIA: implications for definition

Introduction Transient isolated brainstem symptoms (eg, isolated vertigo) are not TIAs by NINDS Diagnostic Criteria, but there are too few data on their prognosis to be confident of their nature. If some of these are vertebrobasilar (VB) TIAs, then they should be common in the days prior to definite VB ischaemic events. Methods We prospectively studied all first TIA and ischaemic stroke in a population-based study from 2002–2010. Definite events were defined as either a stroke or NINDS-defined TIA with ≥50% symptomatic stenosis. Details of TIAs/transient neurological attacks (TNAs) in the preceding 90 days were recorded. Results Of 1926 ischaemic events, 308 had definite VB events and 809 had definite carotid events. TNAs were more common 90 days prior to VB events than before carotid events (OR=2.86, 2.04–4.02, p<0.001). Of all definite VB events, 79 (25.6%, 20.7–30.5) had at least one TNA/TIA in the preceding 90 days (median=7.0 days) of which only 9 (11.4%) fulfilled NINDS criteria for TIA. The other 70 cases included isolated vertigo (n=25), binocular visual disturbance (16) and vertigo with non-focal symptoms (12). Preceding TNAs were associated with ≥50% symptomatic VB stenosis (OR=2.2, 1.15–4.28). Conclusion In patients with definite VB TIA or stroke, preceding transient isolated brainstem symptoms occurred in 26%. Despite this close temporal link and association with ≥50% symptomatic VB stenosis, only 11% of preceding events satisfied the NINDS definition of TIA.