For the right diagnosis differentiation between stroke types is necessary. Diagnostic tests are also needed to rule out
other brain diseases, to get an impression of the likely underlying cause of brain ischaemia,to assess the prognosis,
to provide a basis for physiological monitoring of the stroke patient and to identify concurrent diseases or
complications associated with stroke that may influence prognosis.
Various diagnostic methods are used after acute stroke, amongst which cranial computed tomography is the most
important. Magnetic resonance imaging, ultrasound studies, electrocardiography and laboratory tests are also
used for diagnosis in order to determine the most appropriate treatments. The diagnostic methods give information
about the severity of stroke and about general clinics (ABC, internal, co-morbidity).
References:
EUSI Recommendations. 2002, www.eusi-stroke.com
Fiebach JB, Schellinger PD. Springer Verlag, Darmstadt 2003.
Diagnostic Procedures - Cranial computed tomography (CCT).
For a long time, CT has been the mainstay of imaging diagnostics after acute stroke. Although the definite size of
the infarct is not usually clear until 2 or 3 days after stroke onset, there are early changes that may be visible as
soon as 2 or 3 hours after stroke onset. Haemorrhages can be detected as early as a few minutes after onset; however,
growth of haemorrhage is a frequent finding. Subarachnoid haemorrhage is also best detected by CT scanning (in 95% of
cases). In the past, CT scanning has helped to identify other morphological reasons for acute neurological symptoms,
but for this purpose it has now been replaced by MRI imaging.
New technologies, such as perfusion CT and CT angiography, may become available in more and more centres throughout
the world. Therefore, CT scanning will remain the number one imaging technology in most centres, although MRI imaging
has some advantages, but also some disadvantages.
References:
EUSI Recommendations. 2002, www.eusi-stroke.com.
Fiebach JB, Schellinger PD. Springer Verlag, Darmstadt 2003.
Diagnostic Procedures - Magnetic resonance imaging (MRI)
Another alternative in stroke imaging is the MRI technology including magnetic resonance imaging (MRI), magnetic
resonance angiography (MRA), diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). In addition to
morphological imaging (T1), DWI and and PWI help to differentiate infarcted tissue from ischaemic tissue at risk.
Further the method identifies ischaemic lesions in the posterior fossa reliably. MRA gives information on vascular
status including the venous system and may identify aneurysms larger than 3 mm in diameter.
In recent years, there have been many publications on MRI technology as an alternative in stroke imaging.
Diffusion- and perfusion-weighted images, the so- called mismatch concept, MRA and the recent data on the reliable
identification of the very early parenchyma haemorrhages have helped to promote this technology. However, there are
some disadvantages inherent in MRI scanning, including
- the more complex diagnostic procedure that still requires 15 minutes for a complete study,
- the fact that many patients do not tolerate MRI scanning, especially in cases of severe stroke, where patients cannot be reliably monitored during the scanning period,
- the fact that it is not available 24 hours and 7 days a week in most centres.
It is an interesting technology that in some large referral centres is used instead of CT scanning in the majority
of cases, but in most centres will remain a tool for subacute elective imaging rather than for emergency diagnosis.
In addition, MR technology is increasingly used in clinical trials, especially in phase II as additional assessment for
a proof of concept as an endpoint measure.
MRI Based Patient Selection
References:
EUSI Recommendations. 2002, www.eusi-stroke.com.
Fiebach JB, Schellinger PD. Springer Verlag, Darmstadt 2003.
Schellinger et al. Der Nervenarzt 2001; 72: 907-917.
Kidwell et al. Stroke 2002; 33: 95-98.
Diagnostic Procedures - Electrocardiogram (ECG)
Electrocardiogram is essential because there is a high incidence of heart involvement in stroke patients and a
coincidence of stroke and myocardial infarction. In addition there are several other issues of interest. Rarely,
stroke may cause acute arrhythmias not previously known to be present. In other cases atrial fibrillation was not
known, but was probably present before the stroke happened. The ECG helps to detect atrial fibrillation as a possible
cause of embolic stroke. Some strokes may also cause ECG changes and sometimes CKMB elevation (Oppenheimer, Furlan).
Finally, some of the neuroprotective drugs that are currently being evaluated for stroke may influence the ECG.
Therefore an ECG is an essential part of the screening process of patients who may be candidates for new treatment
protocols.
References:
EUSI Recommendations. 2002, www.eusi-stroke.com
Furlan AJ, Hinchley JA. In Ginsberg MD, Bogousslavsky,1998; 115: 1610-1617.
Oppenheimer SM. Curr. Opin Neurol 1994; 7 (1): 20-24.
Diagnostic Procedures - Ultrasound studies
Ultrasound studies include continuous wave (cw) and pulsed wave (pw) - Doppler and/or duplex sonography of the
extracranial and the basal intracranial arteries (TCD), and helps to identify stenosis or occlusion, vasospasm,
state of collaterals, and recanalisation.
While ultrasound is very popular in Europe, in other regions acute ultrasound studies are not part of the routine
evaluation of stroke patients. Rather, ultrasound is done in the post-acute situation, and not usually by physicians,
but by ultrasound technicians. In trained hands, diagnostic ultrasound including B-mode imaging of the carotids and
colour-coded transcranial doppler ultrasound is an extremely useful adjunct to CT scanning and clinical assessment.
In fact, the results from early ultrasound studies may help early identification of stroke causes. The results of
ultrasound are highly correlated with those of angiography and are considered, by some, to be more reliable than
the results from MRI, which sometimes overestimates the degree of stenosis. On the other hand, time delays
because of waiting times for ultrasound should not be tolerated. Ultrasound should only be used, if it can be
done without undue delays in the emergency situation. One of the major benefits is that ultrasound studies can
be repeated almost daily, are relatively inexpensive, and are not at all risky.
References:
EUSI Recommendations. 2002, www.eusi-stroke.com
Schellinger et al. In Fiebach JB, Schellinger PD, 2003: 83-90.
Diagnostic Procedures - Laboratory tests
Although laboratory tests have also never been subjected to a prospective randomized trial, the use of laboratory
tests in the early assessment of acute stroke patients is common sense. The question is, however, how extensive
these tests should be. The EUSI recommendations propose a rather limited, though comprehensive panel of laboratory
tests, including haematological parameters (rbc, wbc, platelet count), basic clotting parameters, electrolytes, renal
and hepatic chemistry, cardiac enzymes, CRP and sedimentation rate, as a basis for early decision-making processes.
In fact, even though clotting parameters are collected, the decision to use thrombolytic therapy in a given patient
is not dependent on the results of the clotting tests.
Reference:
EUSI Recommendations. 2002, www.eusi-stroke.com
MRI Based Patient Selection
In recent years, much emphasize has been put on the development of better imaging strategies in the identification
of patients suitable for thrombolytic therapy. Although diffusion/perfusion weighted MRI is not yet available everywhere,
the number of centres that can provide this technology to their patients is ever increasing. The mismatch concept is the
technology on which this method of patient selection is based. Mismatch decreases over time, but may be found in
individual patients as late as 12 h. This may help to increase the time window for acute therapy and allow
treatment in patients without known stroke onset time. The practical issues incude a 15-20 min scan time, but
some patients don´t tolerate MRI study.
References:
Warach et al. Ann. Neurol 2000; 48 (5): 713-722.
Kidwell et al. Stroke 2002; 33 (1): 95-98.,
Jansen et al. Der Nervenarzt 1998; 69 (6): 465-471.
Schellinger PD, Fiebach JB. In Fiebach JB, Schellinger PD, 2003: 31-34.
Stroke MRI – The Concept
A complete MRI stroke assessment includes MR angiography to obtain information about the status
of the large brain vessels (1). It includes a T2 weighted image, which is extremely sensitive, to rule out haemorrhages
(2). Diffusion weighted images depict some area of the brain, which maybe thought to be educative for the cure of the
infarct (A). There are reports that in very early scans, maybe found, which diffusion abnormalities disappear later
on, but this is a not very frequent finding and it is absolutely rare that the diffusion abnormalities disappear
completely.
The perfusion-weighted image gives an idea of areas of the brain that are malperfused (B). According to the hypothesis
of the mismatch concept, the difference between the diffusion-weighted image of the lesion and the perfusion-weighted
image area gives an idea of a tissue at risk or, a tissue that may be saved by acute thrombolytic therapy (C). This is
an area, which has received lots of interest in the past. For more information refer to the numerous publications
on this and the recent training book by Fiebach and Schellinger on Stroke MRI, in which an exhaustive list of
references may be found.
Reliable Detection of intracranial haemorrhage (ICH) by MRI?
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| CT |
PWI |
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T2*WI |
| Courtesy Drs Jansen, Fiebach and Schellinger (Kiel; Heidelberg) |
A major question is whether MRI identifies intracranial haemorrhage reliably. While this was
questioned until a couple of years ago, most radiologists and stroke neurologists are now convinced, that MRI does
detect intra-parenchymal haemorrhage easily. The remaining problematic area is the detection of subarachnoid
haemorrhage. In clinical practice this rarely represents a differential-diagnostic problem. Therefore, many
centres would accept that individual patients may be treated with thrombolytic therapy on the basis of MRI studies
alone, without an earlier CT scan, in order to save time. The most sensitive T2* weighted images come easily as the
basis for the diffusion-weighted images and can be achieved without any additional time delay.
Most radiologists and stroke neurologists are now convinced, that MRI can detect intra-parenchymal haemorrhage reliably.
The detection of subarachnoid haemorrhage is more problematic. In practice this rarely represents a
differential-diagnostic problem so, to save time, many centres accept that individual patients with ischaemic stroke can be treated with
thrombolytic therapy on the basis of MRI studies without an earlier CT scan. The most sensitive T2 * weighted images
come easily as the basis for the diffusion-weighted images and can be achieved without delay.
Reference:
Schellinger PD, Fiebach JB. In Fiebach JB, Schellinger PD, 2003: 35-44.
Better Patient Selection by Dynamic MRI – after 2.5 h onset?
| Case 1: 2.5 h after onset, NIHSS 15 |
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| MRI |
DWI |
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PWI |
| Courtesy Drs Jansen, Fiebach and Schellinger (Kiel; Heidelberg) |
In this illustrative case, 2.5 hours after stroke onset MRI shows an occlusion of the proximal M1 segment on the left. DWI-Imaging show the lesion in the frontal part of the left hemisphere with some small spots in a terminal supply area. However, PWI imaging shows a large perfusion abnormality. This represents a very extensive mismatch.
Better Patient Selection by Dynamic MRI – after 24 h onset?
| Case 2: at 24 h, NIHSS 5 |
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| MRI |
DWI |
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PWI |
| Courtesy Drs Jansen, Fiebach and Schellinger (Kiel; Heidelberg) |
24 hours later, after successful thrombolytic therapy, the vessel is recanalized; the diffusion
abnormality is still there, but has not grown and the perfusion deficit is almost gone.
Reference:
Schellinger PD, Fiebach JB. In Fiebach JB, Schellinger PD, 2003: 75-81. |
