Stroke
Stroke accounted for 11.8% of total deaths worldwide and is the second most common single cause of death in Europe,
with great socio-economical impact,
and constitutes a large part of emergency room (ER) presentations[1].
Stroke is caused by sudden insufficient blood flow to brain parenchyma and it can be divided into ischemic (which accounts for 85% of strokes) and hemorrhagic (which accounts for 15%).
Ischemic stroke can be caused by occlusion of either small vessels in the brain or large arteries feeding the brain.
Roughly 25% of strokes are due to large vessel disease,
small vessel disease,
and cardioembolism,
respectively,
yet 25% remain of unknown origin[2].
Imaging studies are essential for diagnosis,
with brain computed tomography (CT) being performed most frequently.
Treatment consists of reestablishing physiological blood flow,
either by thrombolysis (tPA) or mechanical endovascular thrombectomy,
in the most timely manner.
The latest recommendations state that “first picture to puncture time should be less than 90 min.”[3].
With that in mind,
the use of imaging in the ER means most often NECT with subsequent CTA.
Thorough imaging studies are nonetheless essential for further management of the patient,
with the identification of the cause of stroke being paramount.
Imaging Studies
Ultrasound is useful both for evaluating the carotid arteries and the heart in stroke patients.
It is a first-line modality both for screening and diagnostic evaluation of carotid disease and its use is increasing.
However,
despite being non-irradiating,
it suffers from low accuracy and has low inter-observer agreement in characterizing plaques.
Contrast Enhanced Ultrasound offers higher potential,
but it has low ER availability as of writing [4].
Digital Subtraction Angiography (DSA) is the gold standard of vascular imaging,
having the unique advantage of offering the possibility of direct treatment alongside diagnosis.
However,
it has the lowest availability,
highest costs and highest procedure risk of any diagnostic procedure[5].
Its use is therapeutic rather than diagnostic.
Magnetic Resonance Angiography (MRA)offers highly detailed information about both vessel and parenchymal characteristics and is able to describe specific characteristics of plaques with potential future use [6].
Its use in the ER is limited due both to availability and time constraints (both the time needed for the examination and the time needed to ensure the patient’s condition is stable,
MR-safe and the ability to cooperate the examination).
Lastly,
its non-iradiating character is of particular use in patients with potential multiple examinations [7].
CT Angiography (CTA) is the most used vascular study in stroke patients.
It is highly available,
as virtually all CTs can perform adequate CTAs; it is fast,
with scan times being under a minute,
and with patients already being positioned for the head CT; it is thorough,
having the possibility of extending the scan area to include areas of interest with relative ease (i.e.
the heart for suspicion of cardiac emboli); it is highly detailed,
offering information about stenoses,
plaque morphology,
parietal characteristics,
and vessel morphology – information helpful to neurointerventionists when planning an endovascular procedure [4,
8].
Moreover,
there are developments of modified CTA protocols,
such as the multiphase CT,
that can offer useful information on collaterals.
Current recommendations are that ischemic stroke patients be investigated with NECT and CTA[9].