- Email: [email protected]
MRI versus CT in acute stroke
Correspondence
3
4
Hand P, Wardlaw J, Rowat A, Haisma J, Lindley R, Dennis M. MR brain imaging in patients with acute stroke: feasibility and patient-related difficulties. J Neurol Neurosurg Psychiatry 2005; 76: 1525–27. ATLANTIS E and NINDS rt-PA Study Group Investigators. Association of outcome with early stroke treatment: pooled analysis of ATLANTIS, ECASS, and NINDS rt-pa stroke trials. Lancet 2004; 363: 768–74.
Authors’ reply The primary objective of our investigation was to compare the diagnostic information contained in non-contrast CT with that of noncontrast MRI in the full range of patients with stroke-like symptoms presenting to a community hospital. We believe that this situation reflects stroke care provided outside of tertiary care centres since the initial assessment and decision to use imaging was initiated by the emergency physician. The superiority of MRI was driven by a fivefold greater detection of radiological signs of acute ischaemic stroke and a greater degree of diagnostic agreement among expert readers.
Rüdiger von Kummer and Imanuel Dzialowski’s concern about our
Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/
1342
inclusion of patients 8 days from onset neglects several relevant facts: the median time from onset to scan was about 6 h (IQR 3–9); the results were the same when the time from onset to scan was within 12 or 3 h; and limiting the range of patients selected would have made the results less generalisable. To assuage their concern about our definition of infarct versus transient ischaemic attack, we repeated the analysis in all patients with a clinical diagnosis of definite or probable acute ischaemic cerebrovascular syndrome,1 whether or not the deficits were transient or the scan was read as positive by the treating stroke physician. This analysis confirmed the extent of MRI’s superiority in accuracy and sensitivity. Lastly, von Kummer and Dzialowski are concerned that MRI use has not been shown to improve patients’
outcomes. Because patients diagnosed with acute ischaemic stroke are offered interventions of proven clinical benefit (eg, thrombolysis, inpatient stroke units, secondary prevention medicines), greater diagnostic accuracy must of logical necessity lead to better outcomes in stroke patients correctly diagnosed than in their misdiagnosed counterparts. Future studies might quantify the size of that effect.
In summary, perfusion CT combined with CT angiography is an inexpensive and promising alternative in the emergency assessment of stroke patients where access to MRI is unavailable or restricted. Moreover, the advances in CT might soon allow us to guide our decisionmaking regarding thrombolytic treatments in the emergency setting beyond the current 3-h time frame.
We declare that we have no conflict of interest.
We declare that we have no conflict of interest.
*Steven Warach, Julio A Chalela
*Wassilios Meissner, Igor Sibon, François Rouanet, Patrice Ménégon, Jean-Marc Orgogozo
[email protected] Section on Stroke Diagnostics and Therapeutics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Rm B1D733, MSC 1063 Bethesda, MD 20892, USA (SW); Medical University of South Carolina, Charleston, SC, USA (JAC) 1
Kidwell CS, Warach S. Acute ischemic cerebrovascular syndrome: diagnostic criteria. Stroke 2003; 34: 2995–98.
Julio Chalela and colleagues1 stress that MRI is the current gold standard in imaging acute stroke. Indeed, MRI is an invaluable tool with which to visualise, within minutes of cerebral infarction, what is believed to be the core (area that is already dead) and the penumbra (tissue at risk that might either die or survive).2 By contrast, conventional CT has only limited use in detecting acute ischaemic stroke.3 However, the emergency assessment of most stroke patients still relies on CT alone. In recent years, perfusion CT and CT angiography have been introduced in imaging acute stroke. Since then, surrogate markers of perfusion CT that correspond to core and penumbra have been defined.4 There is a good correlation between the core and penumbra as assessed by perfusion CT and MRI.5 One drawback of perfusion CT is the restriction of the anatomical coverage of most multidetector scanners compared with MRI. However, the development of more powerful multidetector CT machines might overcome this limitation. Finally, CT angiography allows the visualisation of the neck and brain arteries with a high resolution.
[email protected] Department of Neurology (WM, IS, FR, JMO) and Department of Neuroradiology (PM), CHU Pellegrin, 33076 Bordeaux cedex, France 1
2
3
4
5
Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison. Lancet 2007; 369: 293–98. Hjort N, Christensen S, Solling C, et al. Ischemic injury detected by diffusion imaging 11 minutes after stroke. Ann Neurol 2005; 58: 462–65. Barber PA, Demchuk AM, Zhang J, Buchan AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy. Lancet 2000; 355: 1670–74. Muir KW, Buchan A, von Kummer R, Rother J, Baron JC. Imaging of acute stroke. Lancet Neurol 2006; 5: 755–68. Wintermark M, Flanders AE, Velthuis B, et al. Perfusion-CT assessment of infarct core and penumbra: receiver operating characteristic curve analysis in 130 patients suspected of acute hemispheric stroke. Stroke 2006; 37: 979–85.
The paper by Julio Chalela and colleagues on MRI in acute stroke1 was assessed in a critical appraisal exercise by 13 participants in an advanced education programme on cerebrovascular diseases, organised by the University “La Sapienza” in Rome, Italy. In a pre-evaluation survey, participants were asked whether, in their opinion, MRI should replace CT for the diagnosis of acute stroke. Answers were almost balanced between “yes” (seven) and “no” (six). Further discussion led the panel to conclude that MRI is: (a) a valid test for acute stroke; (b) more sensitive and specific than CT to diagnose brain ischaemia; (c) as helpful as CT in www.thelancet.com Vol 369 April 21, 2007
3
4
Hand P, Wardlaw J, Rowat A, Haisma J, Lindley R, Dennis M. MR brain imaging in patients with acute stroke: feasibility and patient-related difficulties. J Neurol Neurosurg Psychiatry 2005; 76: 1525–27. ATLANTIS E and NINDS rt-PA Study Group Investigators. Association of outcome with early stroke treatment: pooled analysis of ATLANTIS, ECASS, and NINDS rt-pa stroke trials. Lancet 2004; 363: 768–74.
Authors’ reply The primary objective of our investigation was to compare the diagnostic information contained in non-contrast CT with that of noncontrast MRI in the full range of patients with stroke-like symptoms presenting to a community hospital. We believe that this situation reflects stroke care provided outside of tertiary care centres since the initial assessment and decision to use imaging was initiated by the emergency physician. The superiority of MRI was driven by a fivefold greater detection of radiological signs of acute ischaemic stroke and a greater degree of diagnostic agreement among expert readers.
Rüdiger von Kummer and Imanuel Dzialowski’s concern about our
Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/
1342
inclusion of patients 8 days from onset neglects several relevant facts: the median time from onset to scan was about 6 h (IQR 3–9); the results were the same when the time from onset to scan was within 12 or 3 h; and limiting the range of patients selected would have made the results less generalisable. To assuage their concern about our definition of infarct versus transient ischaemic attack, we repeated the analysis in all patients with a clinical diagnosis of definite or probable acute ischaemic cerebrovascular syndrome,1 whether or not the deficits were transient or the scan was read as positive by the treating stroke physician. This analysis confirmed the extent of MRI’s superiority in accuracy and sensitivity. Lastly, von Kummer and Dzialowski are concerned that MRI use has not been shown to improve patients’
outcomes. Because patients diagnosed with acute ischaemic stroke are offered interventions of proven clinical benefit (eg, thrombolysis, inpatient stroke units, secondary prevention medicines), greater diagnostic accuracy must of logical necessity lead to better outcomes in stroke patients correctly diagnosed than in their misdiagnosed counterparts. Future studies might quantify the size of that effect.
In summary, perfusion CT combined with CT angiography is an inexpensive and promising alternative in the emergency assessment of stroke patients where access to MRI is unavailable or restricted. Moreover, the advances in CT might soon allow us to guide our decisionmaking regarding thrombolytic treatments in the emergency setting beyond the current 3-h time frame.
We declare that we have no conflict of interest.
We declare that we have no conflict of interest.
*Steven Warach, Julio A Chalela
*Wassilios Meissner, Igor Sibon, François Rouanet, Patrice Ménégon, Jean-Marc Orgogozo
[email protected] Section on Stroke Diagnostics and Therapeutics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Rm B1D733, MSC 1063 Bethesda, MD 20892, USA (SW); Medical University of South Carolina, Charleston, SC, USA (JAC) 1
Kidwell CS, Warach S. Acute ischemic cerebrovascular syndrome: diagnostic criteria. Stroke 2003; 34: 2995–98.
Julio Chalela and colleagues1 stress that MRI is the current gold standard in imaging acute stroke. Indeed, MRI is an invaluable tool with which to visualise, within minutes of cerebral infarction, what is believed to be the core (area that is already dead) and the penumbra (tissue at risk that might either die or survive).2 By contrast, conventional CT has only limited use in detecting acute ischaemic stroke.3 However, the emergency assessment of most stroke patients still relies on CT alone. In recent years, perfusion CT and CT angiography have been introduced in imaging acute stroke. Since then, surrogate markers of perfusion CT that correspond to core and penumbra have been defined.4 There is a good correlation between the core and penumbra as assessed by perfusion CT and MRI.5 One drawback of perfusion CT is the restriction of the anatomical coverage of most multidetector scanners compared with MRI. However, the development of more powerful multidetector CT machines might overcome this limitation. Finally, CT angiography allows the visualisation of the neck and brain arteries with a high resolution.
[email protected] Department of Neurology (WM, IS, FR, JMO) and Department of Neuroradiology (PM), CHU Pellegrin, 33076 Bordeaux cedex, France 1
2
3
4
5
Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison. Lancet 2007; 369: 293–98. Hjort N, Christensen S, Solling C, et al. Ischemic injury detected by diffusion imaging 11 minutes after stroke. Ann Neurol 2005; 58: 462–65. Barber PA, Demchuk AM, Zhang J, Buchan AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy. Lancet 2000; 355: 1670–74. Muir KW, Buchan A, von Kummer R, Rother J, Baron JC. Imaging of acute stroke. Lancet Neurol 2006; 5: 755–68. Wintermark M, Flanders AE, Velthuis B, et al. Perfusion-CT assessment of infarct core and penumbra: receiver operating characteristic curve analysis in 130 patients suspected of acute hemispheric stroke. Stroke 2006; 37: 979–85.
The paper by Julio Chalela and colleagues on MRI in acute stroke1 was assessed in a critical appraisal exercise by 13 participants in an advanced education programme on cerebrovascular diseases, organised by the University “La Sapienza” in Rome, Italy. In a pre-evaluation survey, participants were asked whether, in their opinion, MRI should replace CT for the diagnosis of acute stroke. Answers were almost balanced between “yes” (seven) and “no” (six). Further discussion led the panel to conclude that MRI is: (a) a valid test for acute stroke; (b) more sensitive and specific than CT to diagnose brain ischaemia; (c) as helpful as CT in www.thelancet.com Vol 369 April 21, 2007