Detection of Crossed-Cerebellar Hypoperfusion in Acute Stroke using perfusion-weighted MRI

Introduction Crossed cerebellar diaschisis (CCD), the decrease in blood flow and metabolism in the cerebellar hemisphere contralateral to a supratentorial stroke, is observed relatively frequently using imaging techniques such as PET and SPECT (1). In contrast, curiously, there have been almost no reports of corresponding findings (crossed cerebellar hypoperfusion (CCH)) using magnetic resonance perfusion imaging (PWI) in patients with acute stroke (2). This study was undertaken to determine the frequency of observation of CCH in acute stroke by retrospective review of a research database of acute stroke patients evaluated by diffusion-weighted MRI (DWI) and PWI. Material and Methods MRI was performed on 1.5T MRI systems, and consisted of PWI, DWI FLAIR/T2-weighted sequences and MR angiography. PWI images with whole brain coverage were processed to generate maps of time-topeak (TTP) and cerebral blood flow (CBF) using the ‘Penguin’ program (3). PWI and DWI scans from 134 consecutive acute stroke patients, admitted to our stroke service and scanned within 24 hours of symptom onset, were retrospectively reviewed for the presence of cerebellar hypoperfusion contralateral to an acute supratentorial infarct seen on DWI. The presence of hypoperfusion was defined as TTP ≥ 4 seconds compared to the contralateral hemisphere (4), with an absence of cerebellar abnormalities on T2-weighted scans, DWI, or disease of the vertebrobasilar system on MRA. Results 4 out of 134 cases (2.98%) met the criteria of CCH. Examples of DWI and PWI for 3 of the cases are shown in Figure 1. CCH was best visualized on reconstructed TTP maps, as opposed to CBF, however CBF reductions (contralateral to ipsilateral cerebellar hemisphere) of 29.0%, 26.4%, 56.9% and 30.2% were found in the 4 cases, respectively.