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Haemorrhagic strokes (intracerebral haemorrhage [ICH] and subarachnoid haemorrhage [SAH]), caused by
ruptured blood vessels, constitute 26% of all strokes, and have very high rates of mortality and morbidity. Ischaemic
strokes, resulting from the occlusion of brain blood vessels by a buildup of arterial atherosclerotic plaques or by an
embolus from another blood vessel, account for the majority (71%) of all strokes. The distinction between haemorrhagic
and ischaemic stroke is critical in stroke diagnosis, because acute treatments and preventative strategies often bring a
risk of haemorrhage, which would be detrimental in the setting of haemorrhagic stroke. The prevalance of stroke subtypes
differs between populations. For example, African-American and Asian populations have a higher incidence of haemorrhagic
stroke, and according to evidence from the Northern Manhattan Stroke Study, Hispanic populations may also have a slightly
higher incidence of haemorrhagic strokes (see chapter 1.2).
Stroke Subtypes
Reference:
Foulkes et al. Stroke 1988; 19: 547-554.
| Stroke subtypes from an unselected population |
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| Intracerebral haemorrhage |
15% |
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| Subarachnoid haemorrhage |
5% |
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| Large vessel disease (incl. embolic) |
35% |
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| Small vessel disease |
25% |
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| Unknown cause |
20% |
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References:
Mohr et al. Neurology 1978; 28: 754-762.
Adams et al. Stroke 1993; 24 (1): 35-41. |
The data are not based on large-scale epidemiological statistics, rather, on an estimate of the distribution as we
see it in large clinical referral centres. This distribution may differ in clinical trials and between centres, because
patient selection plays a major role.
For example, in thrombolysis trials, the representation of small-vessel disease was lower than is indicated here.
In addition, the number of patients who are considered to have “stroke of unknown origin” may vary from centre to
centre and is heavily dependent on whether the individual physician has identified the reason for the stroke or not.
We did not include here, however, a group of patients that is currently becoming more and more frequent: those in whom
several possible reasons for stroke have been identified, but in whom the cause of the index stroke cannot be determined,
e.g. a patient who has mild to moderate carotid artery stenosis, atrial fibrillation and who, on CT-scans, exhibits
signs of advanced microvascular disease.
 
Subtypes of Ischaemic Stroke According to TOAST Criteria
| The TOAST classification denotes five subtypes of ischaemic stroke: |
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| 1) |
large-artery atherosclerosis |
| 2) |
cardioembolism |
| 3) |
small-vessel occlusion |
| 4) |
stroke of other determined etiology |
| 5) |
stroke of undetermined etiology |
Reference:
Adams et al. Stroke 1993; 24 (1): 35-41.
Reference:
Grau et al. Stroke 2001; 32: 2559-2566.
TOAST (Trial of Org 10172 in Acute Stroke Treatment)
TOAST was a 38 centre randomized, double-blind, placebo controlled trial of the low molecular weight
heparinoid , Org 10172 in the treatment of acute ischaemic stroke. The outcome was assessed at 7 days and 3 months after
stroke using the Barthel Index (BI) and Glasgow Outcome Scale (GOS).
BACKGROUND AND PURPOSE:The etiology of ischaemic stroke affects prognosis, outcome, and management. Trials of therapies for
patients with acute stroke should include measurements of responses as influenced by subtype of ischaemic stroke.
A system for categorization of subtypes of ischaemic stroke mainly based on etiology has been developed for the Trial
of Org 10172 in Acute Stroke Treatment (TOAST). METHODS: A classification of subtypes was prepared using clinical
features and the results of ancillary diagnostic studies. "Possible" and "probable" diagnoses can be made based on the
physician's certainty of diagnosis. The usefulness and interrater agreement of the classification were tested by two
neurologists who had not participated in the writing of the criteria. The neurologists independently used the TOAST
classification system in their bedside evaluation of 20 patients, first based only on clinical features and then after
reviewing the results of diagnostic tests.
RESULTS:The TOAST classification denotes five subtypes of ischaemic stroke: 1) large-artery atherosclerosis, 2)
cardioembolism, 3) small-vessel occlusion, 4) stroke of other determined etiology, and 5) stroke of undetermined etiology.
Using this rating system, interphysician agreement was very high. The two physicians disagreed in only one patient. They
were both able to reach a specific etiologic diagnosis in 11 patients, whereas the cause of stroke was not determined
in nine.
CONCLUSIONS: The TOAST stroke subtype classification system is easy to use and has good interobserver agreement.
This system should allow investigators to report responses to treatment among important subgroups of patients with
ischaemic stroke. Clinical trials testing treatments for acute ischaemic stroke should include similar methods to
diagnose subtypes of stroke. |
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© 2005 Boehringer Ingelheim GmbH, Germany. All rights reserved.
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