Diagnosis of stroke on neuroimaging
BMJ 2004; 328 doi: https://doi.org/10.1136/bmj.328.7441.655 (Published 18 March 2004) Cite this as: BMJ 2004;328:655
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We agree with Wardlaw and Farrall (1) that a “scan all immediately”
strategy for stroke is optimal. The editorialists indicate that while MRI
has advantages in imaging acute stroke, there are some perceived
disadvantages.
It has been our experience that the advantages of an early imaging
strategy with MRI outweighs disadvantages. By combining diffusion weighted
imaging with a T2 weighted gradient sequence there is a high sensitivity
to both infarction and haemorrhage. The room times for this technique are
similar to CT and most patients can be scanned by MRI (2) . The
interpretation of the scans are more straightforward and have high
reproducibility (3).
In a British DGH where there may not be ready access to a specialist
neuroradiologist or stroke specialist, we feel MRI with diffusion-weighted
imaging carries significant advantages in ease of interpretation with a
higher sensitivity and specificity compared to CT scanning, particularly
in patients in whom the diagnosis is less obvious.
1. Wardlaw JM, Farrall AJ. Diagnosis of stroke on neuroimaging. BMJ
2004;328:655-6.
2. Buckley BT, Wainwright A, Meagher T, Briley D. Audit of a policy of
magnetic resonance imaging with diffusion-weighted imaging as first-line
neuroimaging for in-patients with clinically suspected acute stroke.
Clinical Radiology 2003;58:234-237.
3. Schulz UGR, Briley D, Meagher T, Molyneux A, Rothwell PM. Sensitivity
of diffusion weighted MR-Imaging performed several weeks after a minor
stroke or TIA. JNNP 2003;74:734-8
Competing interests:
None declared
Competing interests: No competing interests
Colleague Sellar suggests that CT scans are far too costly,
(especially due to new European laws) and coming as he does from Scotland
his credibility on economic matters might be all too uncritically
accepted.
Here in Germany, my remuneration is about €100
(state regulated, "GOÄ"). This dramatically reduces my need
for ancillary staff, I have never used a radiographer (the age of
mouseclicks is upon us) for an out-of-working hours exam. and since this
service is offered on a private/commercial basis, I have to drag myself
out of bed,punctually (?) as usual, the next morning.
Yours Faithfully, Tim Morley
Competing interests:
None declared
Competing interests: No competing interests
Editor - Wardlaw and Farrall are to be congratulated on their
important reminder that appropriate and timely neuroimaging can save lives
and improve outcomes in patients with strokes. Undoubtedly earlier
diagnosis is essential if the full benefits of early intervention are to
be realized. For those of us who remember the dark days when patients
with strokes were "written off" the new diagnostic technology and the
current innovative therapies herald an exciting era in the management of
stroke patients.
Of course the other side of the coin is that physicians and the
general public need to be aware of the early signs and symptoms of stroke.
This is particularly important in the case of previously healthy young
women who are on oral contraceptives. Some of these preparations have
been associated with arterial thromboembolism, cerebral thrombosis and
cerebral hemorrhage. Early diagnosis and appropriate treatment will
certainly help to minimize the impact of such life-threatening
complications, particularly when relatively young individuals are
involved.
Competing interests:
None declared
Competing interests: No competing interests
The editorial "Diagnosis of stroke on nueroimaging" with its subtitle
"scan all immeadiately" strategy improves outcomes and reduces cost is not
born out by the evidence base. By far the largest randomised controlled
studies on the use of aspirin in acute stroke were IST and CAST which
published side by side. The latter study states that "for about 800 of the
40,000 patients in CAST and IST; the initial diagnosis was wrong, and the
patient had had a haemorrhage before randomisation. There was no
indication in either trial, however, that these misdiagnosed patients were
damaged by aspirin so any hazard cannot be large"(1).So how does the
proposed emergency scan improve outcomes?
The policy of "scan all immeadiately" also has cost implications not
considered by the authors. They calculate that scanning costs will be £44-
103. This is derived at by taking the running costs of a CT scanner and
dividing this by the number of scans performed. This will not now work.
The authors state that the average District General Hospital will have to
do 3 extra scans a day. If one of these is done out of hours the new
European working time directive will require all of those involved,
typically a consultant radiologist, a radiographer and a nurse to take
most of the following day off. These professionals will require replacing
at a cost of about £ 140,000 year on top of that £44 costing of the
scan.
In summary the policy "scan all immeadiately", although a good
slogan, fails to do what it says on the tin; it doesnt improve outcomes
and could seriously damage the health of radiology departments. Finally
should the academics who wrote the editorial have declared as one of their
interests that they don't do on call?
1 CAST: a randomised placebo-controlled trial of early aspirin use in
20 000 patients with acute ischaemic stroke
The Lancet 1997; 349: 1641-1649
Competing interests:
None declared
Competing interests: No competing interests
The project (reference 12 in the article) has now been published in
the HTA monograph series (volume 8, number 1).
Further details are at this URL:
http://www.ncchta.org/project.asp?PjtId=1073
Competing interests:
None declared
Competing interests: No competing interests
The value of acute stroke imaging. Better the devil you know!
For the vast majority of stroke physicians, the conclusions reached by Professor Wardlaw and colleagues in their recent NHS health technology assessment study1 would not be regarded as being in any way controversial. The authors should be congratulated on providing this data however, as the potential value of obtaining a rapid clinico-radiological stroke diagnosis is still questioned in some circles.
It is interesting to compare the approach of health systems to management of the most common and potentially serious acute vascular syndromes. In suspected acute coronary syndromes, many organizations set a benchmark of 10 minutes between hospital arrival time, completion of an initial clinical assessment and an electrocardiograph2. This information plus, later return of biomarker levels, enable risk stratification and facilitate appropriate acute and preventive therapies. A similar philosophy of urgency in stroke management has traditionally been lacking. This is despite evidence that in ischaemic stroke, improved outcomes are seen when reperfusion is initiated early3. The evidence provided by Wardlaw and Farrell may assist in changing attitudes towards urgency in stroke imaging, however, challenges will remain in translation and implementation at the local level. A hyperacute stroke assessment and management algorithm using a risk stratification approach has recently been introduced across 29 Emergency Departments in NSW Australia4. The package is currently under evaluation, however, the key assessment components are a standardized stroke severity scale and guidelines for immediate, urgent or less urgent non-contrast head CT scanning.
As Wardlaw and Farrell indicate, CT scanning can be combined with angiographic and perfusion imaging, adding 10-15 minutes to scanning time, but providing information on large artery patency and cerebral perfusion. CT perfusion (CTP) and CT angiography (CTA) images from one of our patients are below. The CTP colour maps have been converted to black and white. The patient was imaged at 4 hours after stroke onset with a large area of left middle cerebral artery (MCA) ischaemia. Non-contrast CT (not shown) was normal. CTP maps (top row) show large areas of reduced cerebral blood flow (CBF) and delayed mean contrast transit time (MTT), with a smaller region of reduced cerebral blood volume (CBV). Preliminary evidence suggests that tissue with reduced CBF and normal CBV is at risk of infarction but still potentially salvageable, whereas tissue with reduced CBV is likely to be destined for infarction.5 CTA shows distal M1 MCA occlusion (arrow). The patient was given tPA, and transcranial ultrasound demonstrated recanalisation of the MCA during tPA infusion, with improvement in the National Institutes of Health Stroke Scale from a score of 21 at baseline to 13 immediately post tPA. Follow-up CT shows that the final infarct is very similar in size to the acute CBV lesion (arrows) and that much of the tissue that had decreased CBF but normal CBV acutely was salvaged from infarction.
These newer CT techniques provide additional diagnostic detail and sophistication and, if further validated may be useful in the identification of critically hypoperfused but potentially salvageable tissue, the “ischaemic penumbra”.
We completely agree with the "scan all immediately" recommendation. Patients with
stroke should not be denied the newly proven benefits of rapid radiological diagnosis
of their "brain attack". Furthermore, improvements in stroke assessment will be vital
to promote new research in acute interventions. This should be a public health
priority.
1. Wardlaw JM, Seymour J, Cairns J, Sandercock PAG, Keir S, Lewis SC, et al. What is the best imaging strategy for acute stroke? NHS Health Technology Assessment Project No 96/08/01. Southampton: HTA Monographs, 2003 (in press). www.ncchta,org (accessed 30 Dec 2003).
2. Aroney CN, Boyden AN, Jelinek MV, Thompson P, Tonkin AM, White H. Management of unstable angina. Guidelines 2000. Med J Aust 2000; 173 Suppl: S65-88.
3. The ATLANTIS ECASS 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. The Lancet. 2004;363:768-774
4. Towards A Safer Culture (TASC) Program. http://www.racp.edu.au/hpu/cssp/cands3.htm
5. Wintermark M, Reichhart M, Thiran J-P, et al. Prognostic accuracy of cerebral blood flow measurement by perfusion computed tomography in acute stroke patients. Ann Neurol. 2002;51:417-432.
Competing interests:
None declared
Editorial note
The patient whose case is described has given signed informed consent to publication.
Competing interests: No competing interests