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(Stroke. 2007;38:1134.)
© 2007 American Heart Association, Inc.

Letters to the Editor

Response to Letter by Sohn et al

Department of Radiology, Hospital Dr Josep Trueta, Girona, Spain

Yolanda Silva, MD, PhD

Department of Neurology, Hospital Dr Josep Trueta, Girona, Spain

Sebastian Remollo, MD; Josep Puig, MD; Ana Quiles, MD Eva Gomez, MD

Department of Radiology, Hospital Dr Josep Trueta, Girona, Spain

Mar Castellanos, MD, PhD Joaquín Serena, MD, PhD

Department of Neurology, Hospital Dr Josep Trueta, Girona, Spain

Antoni Davalos, MD, PhD

Department of Neurosciences, Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Spain

Response:

We appreciate the comments by Sohn et al concerning our study comparing preperfusion and postperfusion magnetic resonance angiography (MRA) in acute stroke.¹ After studying 10 patients with postperfusion MRA and digital subtraction angiography, Sohn et al suggested that most cases of better middle cerebral artery flow after contrast are attributable to collateral flow. We would like to make some observations regarding their findings.

The results we reported suggest a rather more complex scenario. All the patients in Sohn’s study had TIMI 0-I flow before contrast administration and TIMI II after contrast (10/10), as compared with only 29% (9/31) of the patients in ours. Most of our patients (16/31) did not show flow improvement, maintaining a TIMI score of 0 to 1. Furthermore, a small group (5/31) showed a large improvement in flow, from TIMI 0-I to TIMI III. This fact suggests the existence of real anterograde flow and makes retrograde-collateral flow unlikely.

As the authors state, the time period between the 2 examinations (MRI and digital subtraction angiography) was an average of 76 minutes, and it is possible that progression from stenosis with distal flow to complete occlusion with collateral flow could occur during this time.

Sohn et al do not mention whether patients were examined with transcranial Doppler immediately after MRI. Transcranial Doppler² or even a fast phase contrast sequence³ can be used to demonstrate middle cerebral artery flow reversal.

Sohn’s observation that postcontrast-enhanced MRA flow voids represent complete occlusion with distal retrograde collateral filling does not concur with the reported results in severe stenosis of the internal carotid artery,⁴ where contrast-enhanced MRA presented a tendency to overestimate carotid stenoses and digital subtraction angiography showed better flow.

We agree with the authors that collateral flow must be an explanation for the distal flow after proximal middle cerebral artery stenosis in some cases. Further studies with contrast-enhanced MRA, phase contrast MRA and transcranial Doppler are needed to better understand the hemodynamics of cerebral arterial flow in acute stroke.

The most important conclusion, which we all agree on, is that postperfusion MRA is highly useful for accurate assessment of middle cerebral artery flow in acute stroke.

Acknowledgments

Sources of Funding

This work was supported by a grant from the Fondo de Investigaciones Sanitarias (PI021083) and by the Fundación Doctor Josep Trueta.

Disclosures

None.

References

1. Pedraza S, Silva Y, Mendez J, Inaraja L, Vera J, Serena J, Davalos A. Comparison of preperfusion and postperfusion magnetic resonance angiography in acute stroke. Stroke. 2004; 35: 2105–2110.[Abstract/Free Full Text]

2. Burgin WS, Malkoff M, Felberg RA, Demchuk AM, Christou I, Grotta JC, Alexandrov AV. Transcranial Doppler ultrasound criteria for recanalization after thrombolysis for middle cerebral artery stroke. Stroke. 2000; 31: 1128–1132.[Abstract/Free Full Text]

3. Ho SS, Chan YI, Yeung DK, Metreweli C. Blood flow volume quantification of cerebral ischemia: comparison of three noninvasive imaging techniques of carotid and vertebral arteries. AJR Am J Roentgenol. 2002; 178: 551–556.[Abstract/Free Full Text]

4. Borisch I, Horn M, Butz B, Zorger N, Draganski B, Hoelscher T, Bogdahn U, Link JA. Preoperative evaluation of carotid artery stenosis: comparison of contrast-enhanced MR angiography and duplex sonography with digital subtraction angiography. AJNR Am J Neuroradiol. 2003; 24: 1117–1122.[Abstract/Free Full Text]

This Article Extract Full Text (PDF) All Versions of this Article: 38/4/1134    most recent 01.STR.0000259893.32847.e5v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pedraza, S. Articles by Davalos, A. Search for Related Content PubMed PubMed Citation Articles by Pedraza, S. Articles by Davalos, A.