Hyperacute Posterior Circulation Ischemic Stroke: Shed DWI Light.

attacks (tia’s) account for 15-23% of all ischemic strokes/tia,1,2 the prognosis is similar to anterior circulation in terms of persistent functional disability at three months.2,3 they have higher rate of recurrent strokes and tia4 and yet it is Cinderella disease. Baseline national institute of health Stroke Scale (nihSS) is falsely low in patients with pCS and may influence thrombolysis decision.5 the current Canadian Best practice recommendation for Stroke Care6 strongly recommend immediate brain and vascular imaging for all patients with suspected acute stroke patients with computed tomogram (Ct)/ Ct angiography (Cta) or magnetic resonance imaging (Mri) diffusion weighted imaging (dWi) sequence / magnetic resonance angiography (Mra). american heart association guidelines for acute stroke treatment also recommend noninvasive angiography of intracranial vessels if intra-arterial therapy is contemplated7 but suggest non-contrast Ct (nCCt) alone is sufficient for thrombolysis decision. Both the recommendations do not distinguish anterior and posterior circulation stroke and practice pattern for imaging in acute stroke is highly variable. apparently normal nCCt and low nihSS (≤4) may exclude thrombolysis eligible pCS patients presenting in the <4.5 hours (and in selected patients up to six hours but this remains to be proven in further randomized studies8). Magnetic resonance diffusion weighted imaging is better than nCCt to detect early ischemic changes in pCS and Mra would be able to diagnose vertebro-basilar artery occlusion (VBao). Computed tomogram angiography can also reliably detect VBao. But absence of visible occlusion does not always translate to good outcome in patients with early dWi lesion.9 Computed tomogram angiography source images (Si) pc-aSpeCtS ≥8 has been associated with favorable outcome in pCS albeit inconsistently.10 pc-apSpeCt≥7 on dWi has sensitivity of 0.74, specificity of 0.82 and negative predictive value of 0.95 for predicting favorable outcome in pCS11. a similar number for acute basilar artery occlusion is pc-aSpeCtS ≥8 on dWi.12 further Mri perfusion weighted imaging (pWi) can also help in selection of patients for intra-arterial stroke therapies for acute basilar artery occlusion in more reliable manner then Ct perfusion.13 in a retrospective study published in the current issue of the Journal, the role of dWi lesion assessment in hyperacute pCS, as a prognostic marker for early neurological deterioration (end) and unfavorable outcome (ufo) at three months is discussed by lee et al.14 one-third of patients with pCS presented in first six hours and thus were amenable to thrombolysis. all patients were subjected to diagnostic Mri with mean door-to-Mri time of 74±149 minutes for all patients, 30±11 minutes for moderate to severe pCS. the over-all