To report a case of right MCA stroke post mechanical thrombectomy (MT) with favorable outcome despite a core infract estimation of 73ml using RAPID software. 

The advance in CTP technology in acute stroke helped to select successful MT candidates, the most commonly used software is RAPID, it has the highest accuracy and was used in majority of the clinical trials including the DAWN and DEFUSE3, different rCBF threshold can give different core volumes, data has shown the smallest difference between CTP and MRI DWI ischemic core estimate at an rCBF <38% but rCBF <30% is routinely used because of the bias towards underestimation.

We report a case of a 43 year old female who presented with left sided weakness started seconds after she woke up and 1 hour prior to presentation, She was on anticoagulation because of dual mechanical valve replacement and was not a candidate for thrombolysis. She had gaze deviation, hemianopsia, loss of tactile extinction, facial droop and hemiplegia (NIHSS19). Because of concerns for wake up stroke CTP using RAPID was obtained. CT head showed no bleed and ASPECT score of 9/10, CTA showed M1 occlusion, no atherosclerosis and good collaterals however CTP showed a 73ml Core infarct using an rCBF threshold <30% making her not an MT candidate.

The patient was taken for MT and an M1 thrombus was removed(TICI3), time from symptoms onset to needle was 110 minutes, NIHSS decreased to 3 and 0 upon discharge(MRS 0). MRI(DWI) showed right temporal infarct corresponding to an rCBF of <20% and not <30%.

CTP is a piece of the clinical evaluation puzzle and may occasionally overestimate core infarct volume. In selected cases we suggest the use of rCBF value of <20% instead of <30%, this include age, time of onset, ASPECT score and good collateral circulation.