Correspondence
Transient Ischemic Attack — Proposed New Definition
N Engl J Med 2003; 348:1607-1609April 17, 2003
- Article
To the Editor:
We welcome the initiative to redefine transient ischemic attack (TIA), undertaken by the TIA Working Group and described by Albers et al. (Nov. 21 issue).1 However, the definition proposed is impractical. Clear definitions of disease are needed to guide treatment and to enable researchers to conduct studies using similar patient groups. The authors' proposed definition, by requiring brain imaging, replaces an arbitrary time-based definition with an equally arbitrary resource-based definition. If this definition is implemented, the distinction between stroke and TIA will be dependent on the imaging resources available. The diagnosis will depend on whether computed tomography (CT) or magnetic resonance imaging (MRI) is performed, and the judgment about whether an infarct found on imaging is relevant will depend on clinical expertise.
The World Health Organization's current clinical definition of stroke allows for a comparison of stroke incidence rates between different populations.2 Adoption of the proposed definition may undermine these comparisons, particularly in areas where patients with transient symptoms are unlikely to undergo scanning.
We suggest that the definition of TIA remain a clinical one but that the time from the onset to the complete resolution of symptoms and signs be changed from 24 hours to 1 hour. This should overcome the problem of incorrectly labeling structural brain damage as TIA and would avoid an epidemiologist's nightmare.
2 ReferencesMartin M. Brown, M.D., F.R.C.P.
University College London, London WC1N 3BG, United KingdomAnthony Rudd, F.R.C.P.
Guy's and St. Thomas' National Health Service Trust, London SE1 7EH, United KingdomRory McGovern, M.R.C.P.I.
King's College, London SE1 3QD, United Kingdom
rmcgovern@doctors.org. uk 1
Albers GW ,Caplan LR ,Easton JD , et al. Transient ischaemic attack -- proposal for a new definition. N Engl J Med 2002;347:1713-1716
Full Text | Web of Science | Medline2
Stroke -- 1989: recommendations on stroke prevention, diagnosis, and therapy: report of the WHO Task Force on Stroke and other Cerebrovascular Disorders. Stroke 1989;20:1407-1431
CrossRef | Web of Science | Medline
To the Editor:
Albers et al. propose a new definition of TIA that is based on the presence or absence of a biologic end point: acute brain infarction. We have been using this definition for some time, first in a diagnostic trial1 and then in a treatment trial,2 because the cause of TIAs and strokes is the same, and strategies to prevent additional brain attacks are consequently identical.
There are some problems with this new definition, however. First, in most rural areas, patients with symptoms suggestive of acute brain ischemia do not undergo extensive diagnostic evaluation (i.e., diffusion MRI); only CT scanning is performed in most cases. This makes it very difficult to distinguish between TIA and stroke, because CT is substantially less sensitive than MRI in identifying acute cerebral infarction. Second, the new definition still conveys the wrong message, that a TIA with no evidence of brain infarction is rather better than a stroke. A rapid recovery is not always a favorable prognostic sign; if an unstable atherosclerotic plaque is responsible for the symptoms, for instance, it might presage another cerebral event.
For these reasons, we recently decided to replace the term “TIA” with “transient stroke” in our everyday work. This definition conveys a clear message: the onset of symptoms of acute brain ischemia is a medical emergency that suggests the need for rapid action in order to identify the cause and provide proper treatment.
2 ReferencesEnzo Ballotta, M.D.
Antonio Toniato, M.D.
Claudio Baracchini, M.D.
Università degli Studi di Padova, 35128 Padua, Italy
enzo.ballotta@unipd. it 1
Baracchini C ,Manara R ,Ermani M ,Meneghetti G . The quest for early predictors of stroke evolution: can TCD be a guiding light? Stroke 2000;31:2942-2947
CrossRef | Web of Science | Medline2
Ballotta E ,Da Giau G ,Baracchini C ,Abbruzzese E ,Saladini M ,Meneghetti G . Early versus delayed carotid endarterectomy after a nondisabling ischemic stroke: a prospective randomized study. Surgery 2002;131:287-293
CrossRef | Web of Science | Medline
To the Editor:
The proposed new definitions of TIA and stroke present several challenges for clinicians and researchers. The new definition of TIA may exclude many patients from thrombolytic therapy. Current guidelines for the use of thrombolytic therapy exclude patients with a recent stroke, but allow thrombolysis after a recent TIA.1 Under the new definition of TIA, patients with acute stroke and prior transient cerebrovascular symptoms, with MRI evidence of subacute infarction, would be excluded from thrombolytic therapy because of the prior “stroke.” Also, evidence of chronic infarction on brain imaging in a patient who has had prior transient symptoms might be unrelated to the current symptoms; under the proposed definition, the diagnosis would be unclear. In addition, it is unclear how the new definitions of TIA and stroke would change current treatment, or if they should.
As a compromise, we propose that the new definitions serve as a research tool, while the medical community continues to use the old definitions. Research may show that patients with transient brain ischemia, with or without radiographic evidence of brain infarction, have meaningfully different outcomes or responses to treatment. If so, widespread adoption of the new nosology may be in order, despite the conundrums we describe.
1 ReferencesRichard A. Bernstein, M.D., Ph.D.
Mark J. Alberts, M.D.
Northwestern University, Chicago, IL 60611
r-bernstein@northwestern.edu 1
Practice advisory: thrombolytic therapy for acute ischemic stroke -- summary statement: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 1996;47:835-839
Web of Science | Medline
Author/Editor Response
Brown and colleagues advocate redefining stroke by replacing the current arbitrary and artificial temporal criterion of 24 hours with the slightly less arbitrary but no less artificial criterion of 1 hour. Unfortunately, any definition based on time alone is intrinsically illogical. A 60-minute cutoff point is still an inaccurate predictor of underlying tissue status and would misclassify both the approximately 35 percent of patients with ischemic symptoms lasting for less than 60 minutes who have MRI evidence of injury and the approximately 50 percent of patients with ischemia lasting for 61 to 360 minutes who do not have MRI evidence of injury.
The purpose of clinical diagnosis is to identify what happened to the patient, not to facilitate epidemiologic studies. The key issue in distinguishing a TIA from a stroke is whether brain injury has occurred. The diagnosis of TIA should conform to other diagnoses in medicine that are based on all the information available from the history, examination, and laboratory studies. Just as we supplement the clinical examination with imaging to diagnose ischemic versus hemorrhagic stroke, we should do the same for TIA versus ischemic stroke. For epidemiologic studies, when imaging information is unavailable, a cutoff period can be used as an operational criterion for a “clinically probable TIA.” However, when imaging information is available, it should be incorporated with other information to improve the accuracy of the diagnosis of TIA (“laboratory-definite TIA”).1
We concur with Ballotta and colleagues that TIAs and cerebral infarctions are ischemic episodes that have fundamental similarities with regard to mechanism and prognosis. We do not agree with the use of terms that obscure whether brain injury has occurred, such as “transient stroke.” Rather, we advocate continued use of the terms “stroke” and “TIA” to distinguish between ischemic episodes that do cause brain injury and those that do not, with the use of alternative terminology (such as “acute cerebral ischemia” or “brain attack”) when either a stroke or a TIA may have occurred.
Bernstein and Alberts are concerned that the proposed definition of TIA would cause patients with recent transient symptoms and evidence on imaging of subacute infarction to be deprived of thrombolytic therapy. We are not advocating a change in current guidelines for thrombolytic therapy. However, we believe that our proposal will facilitate research to improve the safety and efficacy of this therapy. We suspect that it is the extent of recent brain injury, not the duration of transient symptoms, that determines the risk of hemorrhage associated with thrombolytic therapy. Therefore, a tissue-based definition of TIA may ultimately provide better guidance for thrombolytic decision making.
1 ReferencesJeffrey L. Saver, M.D.
UCLA School of Medicine, Los Angeles, CA 90095Gregory W. Albers, M.D.
Stanford University School of Medicine, Palo Alto, CA 94305J. Donald Easton, M.D.
Brown University Medical School, Providence, RI 02903for the TIA Working Group
- Citing Articles (2)
Citing Articles
1
Susan C. Fagan. (2008) Urgent Need for Secondary Stroke Prevention After Transient Ischemic Attack. The Consultant Pharmacist 23:2, 131-140
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Jos
Castillo, Mar
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