Do We Need a New Definition
of Stroke & TIA as Proposed by the AHA?
No…
Stroke & TIA need to Remain Clinical
Diagnoses: to Change Would be Bonkers!
A/Prof Anne L. Abbott
Neurologist
School of Public Health & Preventive Medicine
Monash University, Melbourne, Australia
Disclosures
My academic work has been funded only by
independent grants & family subsidies
This presentation is proudly supported by the
Bupa Health Foundation
Current Main Stream Definitions
Stroke:
• Is ‘the rapidly developed clinical signs of focal (or global-SAH)
disturbance of cerebral function lasting >24 hours or leading
to death with no apparent cause other than of vascular
origin’. (WHO, 1980)
• Sub-classified using brain/vascular imaging etc.
• Can be confirmed by pathology.
TIA (‘mini-stroke’):
• ‘Episodes of temporary & focal cerebral dysfunction of
vascular origin, rapid in onset which commonly last 2-15
minutes but occasionally up to a day. Resolution is swift &
leaves no permanent neurologic deficit’. (Ad hoc Committee, 1975)
Perceived Limitation
A 24 - hour differentiation has the potential to
delay effective hyper-acute stroke therapies.
For example: ED physicians say ‘why are you
thrombolysing the patient so quickly - how do
you know it's not just a TIA?’
Proposed
New Definitions of
Stroke & TIA
1. Easton et al, Stroke, 2009
2. Sacco et al, Stroke, 2013
Underlying ProposalStroke/TIA are imaging dependent & may be defined
according to MR or CT brain imaging alone,
independent of clinical features:
- type
- severity &
- duration a neurologic deficit
1. Definitions are
Inconsistent,
Open to Interpretation &
De-Standardising (Confusing)
Proposed Definition of TIA
2009 – ‘A transient [not defined] episode of
neurological dysfunction caused by focal brain, spinal
or retinal ischaemia without [imaging evidence of]
acute [not defined] infarction [not defined].’
2009 – or ‘Symptomatic ischaemia [focal/global] with
no [imaging] evidence of infarction [acute or chronic,
focal/global].
2013 –Not given but the 2009 ‘definition’ was
endorsed.
Ischaemic Stroke
2009 - [Imaging evidence of] Infarction of central
nervous system tissue [focal or global].
Later - Can be symptomatic or silent…
Later - Can be diagnosed on just clinical features
such as prolonged deficits lasting days.
2013 - An episode of neurological dysfunction
[symptomatic] caused by focal cerebral or spinal or
retinal infarction.
‘Stroke’
Sacco et al, AHA/ASA, Stroke, 2013
A table of >10 scenarios using 405 words is given.
The term “stroke” should be broadly used to include all of the following:
Definition of CNS infarction: CNS infarction is brain, spinal cord, or retinal
cell death attributable to ischemia, based on
1. pathological, imaging, or other objective evidence of cerebral, spinal cord,
or retinal focal ischemic injury in a defined vascular distribution; or
2. clinical evidence of cerebral, spinal cord, or retinal focal ischemic
injury based on symptoms persisting•24 hours or until death, and
other etiologies excluded. (Note: CNS infarction includes hemorrhagic
infarctions, types I and II; see “Hemorrhagic Infarction.”)
Definition of ischemic stroke: An episode of neurological dysfunction caused
by focal cerebral, spinal, or retinal infarction. (Note: Evidence of CNS
infarction is defined above.)
Definition of silent CNS infarction: Imaging or neuropathological evidence
of CNS infarction, without a history of acute neurological dysfunction
attributable to the lesion.
Definition of intracerebral hemorrhage: A focal collection of blood within the
brain parenchyma or ventricular system that is not caused by trauma.
(Note: Intracerebral hemorrhage includes parenchymal hemorrhages after CNS
infarction, types I and II—see “Hemorrhagic Infarction.”)
Definition of stroke caused by intracerebral hemorrhage: Rapidly
developing clinical signs of neurological dysfunction attributable to a focal
collection of blood within the brain parenchyma or ventricular system that is
not caused by trauma.
Definition of silent cerebral hemorrhage: A focal collection products
within the brain parenchyma, subarachnoid space, or ventricular
system on neuroimaging or neuropathological examination that is not
caused by trauma and without a history of acute neurological dysfunction
attributable to the lesion.
Definition of subarachnoid hemorrhage: Bleeding into the
subarachnoid space (the space between the arachnoid membrane and the
pia mater ofthe brain or spinal cord).
Definition of stroke caused by subarachnoid hemorrhage: Rapidly
developing signs of neurological dysfunction and/or headache because of
bleeding into the subarachnoid space (the space between the arachnoid
membrane and the pia mater of the brain or spinal cord), which is not
caused by trauma.
Definition of stroke caused by cerebral venous thrombosis: Infarction
or hemorrhage in the brain, spinal cord, or retina because of thrombosis
of a cerebral venous structure. Symptoms or signs caused by reversible
edema without infarction or hemorrhage do not qualify as stroke.
Definition of stroke, not otherwise specified: An episode of acute
neurological dysfunction presumed to be caused by ischemia or
hemorrhage, persisting•24 hours or until death, but without sufficient
evidence to be classified as one of the above.
Too long & not compatible with 2009
‘Infarction’
2009 - Not actually defined but implied as diagnosed
by brain imaging. Pathologist no longer has a role
2013 - Cell death due to ischaemia diagnosed by
pathology, imaging or >24hr clinical deficit.
Clinician or radiologist can replace the pathologist.
2. Definitions are Scientifically
Flawed
Brain Imaging is Very Useful
But Not all Powerful
•
•
MRI more sensitive than CT in hyperacute ischaemia
MRI-DWI has imperfect
– sensitivity for ischaemia in stroke patients (47- 100%)
– specificity for ischaemia in stroke patients (75-96%)
– May be improved by other parameters (eg rCBF, PWI)
•
MRI lesions can disappear/reverse
•
•
•
Great aid to classify mechanism, prognosis, treatment
Provides different info from the clinical & pathological
Definitions should differentiate these strengths, not nullify
(6.7% esp. reperfusion)
3. Definitions are No Longer Primarily
Clinical or Duration Focused
• Less widely applicable to patients (acutely/later)
• Incompatible with other medical knowledge
- from the past
- from the present/future (esp. about preventing
whole episodes of sustained neurologic deficits)
• Clinical deficit matters most to patients-drives Dx, risk
stratification & Rx. Imaging + pathology help.
Example: Measuring Ipsilateral Stroke Rate
in Asymptomatic Carotid Stenosis
Outlier from
Silvestrini et al. 2010.
- Easton et al 2009…
Average
Annual
Rate of
Ipsilateral Stroke
(Raw data,%)
Updated
Meta-analysis.
After Abbott. Stroke, 2013
2.9
*
Stroke
‘Infarction of central
nervous system tissue’
TIA
‘Transient episode of
neurological
dysfunction caused by
focal ischaemia without
acute infarction.’
???????????????
The Way Forward
• Educate all
- Stroke is bad because of the neurologic deficit.
- Deficit duration exists over a poorly predictable time continuum.
- Rx those most likely to benefit overall, even if some would resolve.
- Aim: Use hyperacute stroke Rx to convert more sustained stroke
deficits into transient deficits.
- Use inclusive terminology for 0-24hrs (stroke/ACVS): then mini stroke vs a sustained stroke.
• Maintain the primarily clinical definition & sub-classify using imaging etc.
• Maintain distinct clinical vs imaging vs pathological terminology.
• Still measure clinical status at baseline & at 24 hrs (somewhat arbitrary
but practical, clinically relevant & highly standardising in research & practice).
References
i. Aho et al: Bulletin of WHO, 1980;59:113-130
ii. Ad Hoc Committee (Anonymous), Stroke 1975;6:564-616
iii. Barber et al Stroke 1999;30:2059-2065
iv. Campbell et l, JCBFM;2011:1-7
v. Easton et al, Stroke; 2009:40:2276-2293
vi. Sacco et al, Stroke, 2013;44:2064-2089
vii. Schafer et al, AJNR 2002;23:1785-1794 & 2003;24:436-443
viii. Schellinger et al 2010:75:177-185
ix. Simonsen et al, Stroke; 2015:46:00-00
x. Tehrani et al Neurology 2014;83:169-173
Acknowledgments
i. Dr Silvestrini, Italy.
ii. Dr Anthony Kam, Consultant Radiologist, Alfred Hospital, Melbourne.
Definition of Definition
‘The meaning of a word using other terms’
Wikipedia
Best definitions will be short,
accurate, consistent, easily & consistently
understood by all & have purpose
The Proposed Definitions Cause
Unnecessary Problems Without Solving
Anything