Dynamic CT perfusion imaging for the detection of crossed cerebellar diaschisis in acute ischemic stroke

Abstract

Objective: Although the detection of crossed cerebellar diaschisis (CCD) by means of different imaging modalities is well described, little is known about its diagnosis by computed tomography perfusion (CTP) imaging. We investigated the detection rate of CCD by CTP imaging and the factors related to CCD on CTP images in patients with acute ischemic stroke.

Materials and methods: CT perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time-to-peak (TTP) obtained from 81 consecutive patients affected by an acute ischemic stroke were retrospectively reviewed. Whole-brain perfusion maps were obtained with a multichannel CT scanner using the toggling-table technique. The criteria for CCD was a unilateral supratentorial ischemic lesion and an accompanying decrease in perfusion of the contralateral cerebellar hemisphere on the basis of CTP maps by visual inspection without a set threshold. Maps were quantitatively analyzed in CCD positive cases.

Results: The criteria for CCD were fulfilled in 25 of the 81 cases (31%). Detection rates per CTP map were as follows: MTT (31%) > TTP (21%) > CBF (9%) > CBV (6%). Supratentorial ischemic volume, degree of perfusion reduction, and infratentorial asymmetry index correlated strongly (R, 0.555-0.870) and significantly (p < 0.05) with each other in CCD-positive cases.

Conclusion: It is possible to detect CCD on all four of the CTP-based maps. Of these maps, MTT is most sensitive in detecting CCD. Our data indicate that CTP imaging is a valid tool for the diagnosis of CCD in patients affected by an acute hemispheric stroke.

Keywords: Acute stroke; CT perfusion; Crossed cerebellar diaschisis.

Fig. 1

Toggling table technique (Jog mode). A. Scanner obtains images during single rotation at location A. B. Table moves upward to locate lower half of object under X-ray tube. C. Scanner obtains images during single rotation at location B. D. Table moves 4 cm in opposite direction from its original position. E. Second cycle of scanning is repeated.

Fig. 2

Perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time-to-peak (TTP) obtained by toggling table technique (Jog mode). 64-year-old female patient with left middle cerebral artery occlusion. Crossed cerebellar diaschisis is demonstrated in right cerebellar hemisphere.

Fig. 3

Crossed cerebellar diaschisis positive case. 73-year-old female patient with hypertension that presented with sudden weakness in left hand. CTP imaging was performed 6 hours after initial onset of symptoms. Each CTP map (MTT, TTP, CBV, and CBF) shows supratentorial and contralateral cerebellar hypoperfusion (low CBV and CBF, delayed MTT and TTP) relative to opposite hemisphere (first and second rows). DWI (third row) shows acute infarction co-localized with supratentorial perfusion abnormality. Co-localized cerebellum (third row) shows no evidence of diffusion restriction. CBF = cerebral blood flow, CBV = cerebral blood volume, CTP = CT perfusion, DWI = diffusion-weighted imaging, MTT = mean transit time, TTP = time-to-peak.

Fig. 4

Measurement of perfusion value and degree of reduction of cerebral perfusion value in each CT perfusion map. Region of interest is placed in affected cerebral hemisphere by manual segmentation and then mirrored to contralateral cerebral hemisphere for assessment of perfusion values. CBF = cerebral blood flow, CBV = cerebral blood volume, MTT = mean transit time, TTP = time-to-peak.

Fig. 5

Measurement of perfusion value and cerebellar asymmetric index representing degree of crossed cerebellar diaschisis in each CT perfusion map. Circular region of interest is placed in cerebellar hemisphere and then mirrored to contralateral cerebellar hemisphere for assessment of perfusion values.