1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b482bd0f-da2a-497c-b4c8-11cf5ff9feaf] => Array
        (
            [runtime-id] => b482bd0f-da2a-497c-b4c8-11cf5ff9feaf
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [0ae6301b-0989-4394-8058-3423af036223] => Array
                        (
                            [runtime-id] => 0ae6301b-0989-4394-8058-3423af036223
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [d62fa10a-8f20-4a3a-a019-42ae67f5fe75] => Array
        (
            [runtime-id] => d62fa10a-8f20-4a3a-a019-42ae67f5fe75
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [5fe33b7f-9f36-4a1a-b2f8-6d817f5b7ef8] => Array
                        (
                            [runtime-id] => 5fe33b7f-9f36-4a1a-b2f8-6d817f5b7ef8
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [4c54ee0d-0ce1-4cbb-98ea-0c7f6934194d] => Array
        (
            [runtime-id] => 4c54ee0d-0ce1-4cbb-98ea-0c7f6934194d
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [4aa49617-0841-4d84-ac48-327e3284ecc9] => Array
                        (
                            [runtime-id] => 4aa49617-0841-4d84-ac48-327e3284ecc9
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b482bd0f-da2a-497c-b4c8-11cf5ff9feaf] => Array
        (
            [runtime-id] => b482bd0f-da2a-497c-b4c8-11cf5ff9feaf
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [0ae6301b-0989-4394-8058-3423af036223] => Array
                        (
                            [runtime-id] => 0ae6301b-0989-4394-8058-3423af036223
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b482bd0f-da2a-497c-b4c8-11cf5ff9feaf] => Array
        (
            [runtime-id] => b482bd0f-da2a-497c-b4c8-11cf5ff9feaf
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [0ae6301b-0989-4394-8058-3423af036223] => Array
                        (
                            [runtime-id] => 0ae6301b-0989-4394-8058-3423af036223
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b482bd0f-da2a-497c-b4c8-11cf5ff9feaf] => Array
        (
            [runtime-id] => b482bd0f-da2a-497c-b4c8-11cf5ff9feaf
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [0ae6301b-0989-4394-8058-3423af036223] => Array
                        (
                            [runtime-id] => 0ae6301b-0989-4394-8058-3423af036223
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b482bd0f-da2a-497c-b4c8-11cf5ff9feaf] => Array
        (
            [runtime-id] => b482bd0f-da2a-497c-b4c8-11cf5ff9feaf
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [0ae6301b-0989-4394-8058-3423af036223] => Array
                        (
                            [runtime-id] => 0ae6301b-0989-4394-8058-3423af036223
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [cf4d6e12-df88-4e44-b4cd-b04a7ab5507a] => Array
        (
            [runtime-id] => cf4d6e12-df88-4e44-b4cd-b04a7ab5507a
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [bba41ff0-3d05-4b2a-952c-a43157dd8bde] => Array
                        (
                            [runtime-id] => bba41ff0-3d05-4b2a-952c-a43157dd8bde
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;c14c5af40c18f623b1ab1966723662ded9b8d7ea
                )

        )

)


  
    
































































    Reply | American Journal of Neuroradiology  
    



















    































    
  
  




    
    

  

      


    

      

  
  
  

    

  

    

  

                
    

      

  

    

  
      
  
  

    


Advertisement



  



  


  
  



  



    

  


  


  


  
  
  
  
  
  

  	      


    
      

    
  
    
        
    

  

    
                        

  

                
    

      

	  

		
		

			

			  

  
      
  
  

    

  
  
      
LetterLetter

  
      

  
      
Reply
  
    	
Peter D. Schellinger and Steven Warach

  
    	
American Journal of Neuroradiology October 2005,  26 (9) 2433-2434; 

  
  
  



  


  
  



			

		

	
	
 	
	  
  

		
		

			

			  

  
      
  
  

    
  


  
  



  
      
  
  

    

  

    

  
      
  
  

    
We very much appreciated the letter of Dr. Liebeskind as well as the opportunity to reply to his comments. Dr. Liebeskind raises an important point with regard to location, thrombus extent, and early vessel signs (EVSs). His major concern is that not only the presence or location of EVSs, which indicate a thrombus, disclose a distinct vascular pathophysiologic correlate. EVS also represent areas with slow blood flow and therefore may indicate the location and extent of compensatory distal collateral flow (1).
First, the statement that the hyperintense fluid-attenuated inversion recovery sign (FLAIR HVS) and the gradient-echo susceptibility vessel sign (GRE SVS) may represent thrombus, as well as slow and/or retrograde flow (FLAIR HVS) of deoxygenated blood (GRE SVS), is entirely accurate and acknowledged in our manuscript in the second paragraph of the discussion (2, p. 622).
As stated in the introduction, our study had 3 objectives, the first and foremost being diagnostic accuracy of early MR imaging vessel signs. For this, the mere presence as compared with MR angiography (MRA)/perfusion-weighted imaging (PWI) and the concordance of location of the occlusion with the most proximal end of the EVS were analyzed. If present (sensitivity of 65.9%), the proximal end of thrombus/occlusion on FLAIR was correlated significantly (r = 0.66; P < .001) with MRA/PWI. For this diagnostic objective it is not relevant whether the further distal extent of the vessel sign is thrombus or slow flow. We do acknowledge, however, the fact that GRE besides its low sensitivity (34.1%) was not at all correlated with MRA/PWI and is often seen more distally. Whether this represents the distal deoxygenated part of the thrombus or collateral flow of deoxygenated blood is not clear. In fact, this could imply that the sensitivity of the hypointense GRE sign for the clot is substantially <34.1%, because the hyperacute, still- oxygenated clot is not seen within 3 hours. Therefore, if necessary, the FLAIR HVS rather than the GRE SVS should be used diagnostically.
Second, we aimed to assess the prognostic value of early MR imaging vessel signs for clinical outcome, recanalization, and intracranial hemorrhage. Here we did not take collateral status into account. We agree with Dr. Liebeskind that a sufficient collateral status likely is a predictor for a good outcome, if recanalization and reperfusion can be rapidly achieved. We believe, however, that there are also patients with thrombus extending from the proximal middle cerebral artery into distal MCA branches beyond the trifurcation. This has been seen on CT scans where the hyperattenuated MCA sign extends into the MCA branches in the Sylvian fissure (dot sign). We concur that, in acute ischemic stroke, it is imperative to consider the location of proximal flow cessation, the location of thrombus, and the location of compensatory collateral flow. We doubt, however, that early MR imaging vessel signs provide this information reliably and arterial spin-labeling techniques for the assessment of local perfusion are far from being routinely applicable in a timely fashion (5 sections, 20 minutes in healthy patients) (3).
Finally, we hypothesized that the MR imaging signal intensity characteristics of early MR imaging vessel signs may reflect the structure of the intraluminal thrombus in patients with a vessel occlusion and can predict response to recombinant tissue plasminogen activator. Here, the presence or absence of good collaterals could be a stronger predictive parameter—and therefore a confounding variable—we take into account. This issue would have been more important if we had detected that clot composition as supposedly reflected by MR imaging EVS is a positive predictor of therapeutic response. In that case a type 1 error might have occurred.
References
  1. ↵
    Liebeskind DS. Collateral circulation. Stroke 2003;34:2279–2284
    Abstract/FREE Full Text
  2. ↵
    Schellinger PD, Chalela JA, Kang DW, et al. Diagnostic and prognostic value of early MR imaging vessel signs in hyperacute stroke patients imaged <3 hours and treated with recombinant tissue plasminogen activator. AJNR Am J Neuroradiol 2005;26:618–624
    Abstract/FREE Full Text
  3. ↵
    Hendrikse J, van der Grond J, Lu H, et al. Flow territory mapping of the cerebral arteries with regional perfusion MRI. Stroke 2004;35:882–887
    Abstract/FREE Full Text
  


  
  



  
      
  
  

    
  


  
  



  




  


  
  



  
      
  
  

    
  


  
  



  
      
  
  

     Back to top  


  
  



			

		

		
		

			

			  

  
        
In this issue

    
  
  

    
  


  
  



  
      
  
  

    

  

    

  
      
  
  

    


Advertisement



  



  


  
  



  



  


  
  



  
      
  
  

    

	  
  

		

          

            

  
      
  
  

     Print  


  
  



  
      
  
  

     Download PDF  


  
  



  
      
  
  

    
 Email Article
  


  
  



  
      
  
  

    
 Citation Tools
  


  
  



          

        

        
        

          

            



  
      
  
  

    

  

    

  
      
  
  

    

  
  
  
  
      
Reply
  
    	
Peter D. Schellinger, Steven Warach

  
    	
American Journal of Neuroradiology Oct 2005, 26 (9) 2433-2434; 

  
  
  



  


  
  



  
      
  
  

    

  
    
  
  
    
  
  
    
  


  


  
  



  
      
  
  

    
del.icio.us logo Twitter logo Facebook logo Mendeley logo
  


  
  



  



  


  
  



  
      
  
  

    
  


  
  



          

        

	
 	
	
	


  


  
  



  
        
Jump to section

    
  
  

    
  


  
  



  
      
  
  

    

  

    
 Related Articles
  • No related articles found.
 Cited By...
  • No citing articles found.
 More in this TOC Section
 Similar Articles

  



  


  
  



			

		

	
	
 	
	
	


    

  



  

                
    

      

  

    

  
      
  
  

    


Advertisement