title: The delayed perfusion sign at MRI.
abstract: OBJECTIVE
  Effective collateral blood flow seem to be an important factor associated with a small infarct volume and a good clinical outcome. We aimed to assess leptomeningeal collateral blood flow on source perfusion-weighted images in patients with acute stroke.
  
  
  METHODS
  29 patients with proximal middle cerebral artery occlusion (MCA alone, n=17; MCA + internal carotid artery [ICA] occlusion, n=12) were evaluated with MRI at baseline before thrombolytic therapy, and at day 60. Clinical evaluation was performed at days 0 and 60 with the National Institutes of Health Stroke Scale (NIHSS) score, and at day 60 with the modified Rankin score. We assessed (on source images of the dynamic contrast-enhanced T2*-weighted perfusion [PWI] sequence) the presence of a hypointensity consistent with delayed contrast arrival within the global perfusion deficit (delayed perfusion sign). We analyzed the extent of the area demonstrating such delayed perfusion (DP area) on source images of the PWI sequence, and compared it with the global perfusion (GP) abnormality shown by time-to-peak maps. We calculated the Spearman rank correlation coefficient between the DP/GP ratio and: 1. age; 2. clinical scores; 3. site of occlusion [MCA alone versus ICA+MCA occlusion]; 4. DWI lesion size at day 0, and T2WI lesion size at day 60; 5. PWI-derived parameters (time-to-peak [TTP], relative cerebral blood volume [rCBV], relative cerebral blood flow [rCBF], and peak height). All tests were bilateral and a p value<0.05 was considered as significant.
  
  
  RESULTS
  Delayed perfusion areas of various size were found within the global perfusion deficit in all patients. High DP/GP ratio values were significantly correlated with: 1. better clinical scores at day 0 and day 60 (all p<=0.04); 2. smaller lesions at day 0 DWI and at day 60 T2WI (all p<=0.004); 3. ICA patency (r=0.49, p=0.01); 4. lower TTP delays, and higher values of rCBV, rCBF, and peak height.
  
  
  CONCLUSIONS
  These preliminary data suggest that a delayed contrast filling observed on native perfusion-weighted images may be a marker of leptomeningeal collateral blood flow, and may lead to better clinical and morphological outcomes in acute ischemic stroke.
authors.affiliation: (1) Service de Radiologie, Hôpital Neurologique et Neurochirurgical P. Wertheimer, BP Lyon Montchat, 69394 Lyon Cedex 03, France.
authors.forename: M
authors.initials: M
authors.lastname: Hermier
authors.forename: A S
authors.initials: AS
authors.lastname: Ibrahim
authors.forename: M
authors.initials: M
authors.lastname: Wiart
authors.forename: P
authors.initials: P
authors.lastname: Adeleine
authors.forename: F
authors.initials: F
authors.lastname: Cotton
authors.forename: P
authors.initials: P
authors.lastname: Dardel
authors.forename: L
authors.initials: L
authors.lastname: Derex
authors.forename: Y
authors.initials: Y
authors.lastname: Berthezène
authors.forename: N
authors.initials: N
authors.lastname: Nighoghossian
authors.forename: J C
authors.initials: JC
authors.lastname: Froment
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002340:Carotid Artery Diseases / Q000150:complications / Q000473:pathology* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003097:Collateral Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000473:pathology* / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008578:Meninges / Q000098:blood supply* / Q000473:pathology* / Q000503:physiopathology; D008875:Middle Aged; D020521:Stroke / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology*; D013997:Time Factors