Abstract:Magnetic resonance imaging (MRI) plays a central role in the early diagnosis of cerebral vascular events. Today, MRI is used not only for the detection of acute ischaemic lesions, but also to fine tune the diagnosis and improve patient selection for early therapeutic decision-making. In this perspective, new tools such as arterial spin labelling (ASL) and susceptibility-weighted imaging (SWI) sequences have been developed. These MRI sequences enable noninvasive assessment of brain damage, providing important d… Show more
“…T2 with gradient recalled echo weighted imaging (T2-GRE) and susceptibility-weighted imaging (SWI) are highly sensitive, and can detect thrombus occlusions in intracranial arteries. Through blooming thanks to a magnetic susceptibility artefact described as the ‘susceptibility vessel sign’, clots may be depicted, located and measured with precise assessment [ 6 ]. Together with time-of-flight magnetic resonance angiography (TOF-MRA), T2-GRE and SWI may identify the site of the occlusion and adjust treatment planning and patient care, as proximal occlusion and clots longer than 8 mm are associated with a low recanalisation rate after IV thrombolysis [ 7 ].…”
Acute ischaemic stroke represents the most common cause of new sudden neurological deficit, but other diseases mimicking stroke happen in about one-third of the cases. Magnetic resonance imaging (MRI) is the best technique to identify those ‘stroke mimics’. In this article, we propose a diagnostic approach of those stroke mimics on MRI according to an algorithm based on diffusion-weighted imaging (DWI), which can be abnormal or normal, followed by the results of other common additional MRI sequences, such as T2 with gradient recalled echo weighted imaging (T2-GRE) and fluid-attenuated inversion recovery (FLAIR). Analysis of the signal intensity of the parenchyma, the intracranial arteries and, overall, of the veins, is crucial on T2-GRE, while anatomic distribution of the parenchymal lesions is essential on FLAIR. Among stroke mimics with abnormal DWI, T2-GRE demonstrates obvious abnormalities in case of intracerebral haemorrhage or cerebral amyloid angiopathy, but this sequence also allows to propose alternative diagnoses when DWI is negative, such as in migraine aura or headaches with associated neurological deficits and lymphocytosis (HaNDL), in which cortical venous prominence is observed at the acute phase on T2-GRE. FLAIR is also of major interest when DWI is positive by better showing evocative distribution of cerebral lesions in case of seizure (involving the hippocampus, pulvinar and cortex), hypoglycaemia (bilateral lesions in the posterior limb of the internal capsules, corona radiata, striata or splenium of the corpus callosum) or in posterior reversible encephalopathy syndrome (PRES). Other real stroke mimics such as mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes (MELAS), Susac’s syndrome, brain tumour, demyelinating diseases and herpes simplex encephalitis are also included in our detailed and practical algorithm.Key points
• About 30% of sudden neurological deficits are due to non-ischaemic causes.
• MRI is the best technique to identify stroke mimics.
• Our practical illustrated algorithm based on DWI helps to recognise stroke mimics.
“…T2 with gradient recalled echo weighted imaging (T2-GRE) and susceptibility-weighted imaging (SWI) are highly sensitive, and can detect thrombus occlusions in intracranial arteries. Through blooming thanks to a magnetic susceptibility artefact described as the ‘susceptibility vessel sign’, clots may be depicted, located and measured with precise assessment [ 6 ]. Together with time-of-flight magnetic resonance angiography (TOF-MRA), T2-GRE and SWI may identify the site of the occlusion and adjust treatment planning and patient care, as proximal occlusion and clots longer than 8 mm are associated with a low recanalisation rate after IV thrombolysis [ 7 ].…”
Acute ischaemic stroke represents the most common cause of new sudden neurological deficit, but other diseases mimicking stroke happen in about one-third of the cases. Magnetic resonance imaging (MRI) is the best technique to identify those ‘stroke mimics’. In this article, we propose a diagnostic approach of those stroke mimics on MRI according to an algorithm based on diffusion-weighted imaging (DWI), which can be abnormal or normal, followed by the results of other common additional MRI sequences, such as T2 with gradient recalled echo weighted imaging (T2-GRE) and fluid-attenuated inversion recovery (FLAIR). Analysis of the signal intensity of the parenchyma, the intracranial arteries and, overall, of the veins, is crucial on T2-GRE, while anatomic distribution of the parenchymal lesions is essential on FLAIR. Among stroke mimics with abnormal DWI, T2-GRE demonstrates obvious abnormalities in case of intracerebral haemorrhage or cerebral amyloid angiopathy, but this sequence also allows to propose alternative diagnoses when DWI is negative, such as in migraine aura or headaches with associated neurological deficits and lymphocytosis (HaNDL), in which cortical venous prominence is observed at the acute phase on T2-GRE. FLAIR is also of major interest when DWI is positive by better showing evocative distribution of cerebral lesions in case of seizure (involving the hippocampus, pulvinar and cortex), hypoglycaemia (bilateral lesions in the posterior limb of the internal capsules, corona radiata, striata or splenium of the corpus callosum) or in posterior reversible encephalopathy syndrome (PRES). Other real stroke mimics such as mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes (MELAS), Susac’s syndrome, brain tumour, demyelinating diseases and herpes simplex encephalitis are also included in our detailed and practical algorithm.Key points
• About 30% of sudden neurological deficits are due to non-ischaemic causes.
• MRI is the best technique to identify stroke mimics.
• Our practical illustrated algorithm based on DWI helps to recognise stroke mimics.
“…The ASL PLD should be optimal because incorrect PLD settings can misrepresent cerebral blood flow [ 4 ]. In adults aged > 70 years old or patients with a suspected neurological condition, it is recommended that PLD be set to 2,000 ms [ 5 ].…”
Section: Discussionmentioning
confidence: 99%
“…In adults aged > 70 years old or patients with a suspected neurological condition, it is recommended that PLD be set to 2,000 ms [ 5 ]. Another solution for misdiagnosis by ASL is that other sequences, such as DWI or MRA, may be useful in confirming the correct diagnosis [ 4 ]. Because this patient's age was 83 years, and his neurological signs suggested the possibility of stroke, ASL was performed with a PLD of 2,025 ms, according to the above recommendation [ 5 ].…”
Section: Discussionmentioning
confidence: 99%
“…ASL can rapidly assess cerebral blood flow using magnetically labeled water in blood as an endogenous tracer. ASL is useful for the evaluation of penumbra zones, localization of the arterial thrombus, post-therapeutic hyperperfusion, and the diagnosis of stroke mimics [ 4 ]. However, whether ASL is a useful technique for evaluating the impending rupture of giant intracranial aneurysms is unknown.…”
An 83-year-old Japanese man was admitted with dysarthria and right hemiparesis. He had had a large intracranial aneurysm on the left internal carotid artery 5 years before admission and had been followed up under conservative treatment. On admission, diffusion-weighted imaging revealed a hyperintense signal on the left anterior choroidal artery territory. Time-of-flight magnetic resonance angiography demonstrated poor visibility of the middle and anterior cerebral arteries and the inferior giant aneurysm, suggesting distal emboli from aneurysm thrombosis or a reduction of blood outflow due to aneurysm thrombosis. Arterial spin labeling (ASL) signal increased in the giant aneurysm, suggesting blood stagnation within the aneurysmal sac, and decreased in the left hemisphere. We diagnosed cerebral infarction due to aneurysm thrombosis, and started antithrombotic therapy. On day 2, he suddenly died of subarachnoid hemorrhage due to rupturing of the giant aneurysm. When thrombosis occurs in a giant aneurysm, increasing ASL signal within the aneurysm and decreasing ASL signal with poor visibility on magnetic resonance angiography in the same arterial territory may indicate the danger of impending rupture of the giant aneurysm.
“…In contrast to LVO, signal abnormalities do not usually conform to a single vascular territory, and an abnormal DWI/FLAIR signal, thought to represent transient vasogenic and cytotoxic oedema, should resolve upon short-interval follow-up imaging [ 25 ]. In cases of diagnostic uncertainty, arterial spin labelling (ASL) may be helpful in discriminating between status epilepticus and infarct, demonstrating elevated cerebral blood flow during ictal and early postictal states [ 26 ]. Fig.…”
Given the rapid evolution and technological advances in the diagnosis and treatment of acute ischaemic stroke (AIS), including the proliferation of comprehensive stroke centres and increasing emphasis on interventional stroke therapies, the need for prompt recognition of stroke due to acute large vessel occlusion has received significant attention in the recent literature. Diffusion-weighted imaging (DWI) is the gold standard for the diagnosis of acute ischaemic stroke, as images appear positive within minutes of ischaemic injury, and a high signal-to-noise ratio enables even punctate infarcts to be readily detected. DWI lesions resulting from a single arterial embolic occlusion or steno-occlusive lesion classically lateralise and conform to a specific arterial territory. When there is a central embolic source (e.g. left atrial thrombus), embolic infarcts are often found in multiple vascular territories. However, ischaemic disease arising from aetiologies other than arterial occlusion will often not conform to an arterial territory. Furthermore, there are several important entities unrelated to ischaemic disease that can present with abnormal DWI and which should not be confused with infarct. This pictorial review explores the scope and typical DWI findings of select neurologic conditions beyond acute arterial occlusion, which should not be missed or misinterpreted.Teaching points• DWI abnormalities due to acute arterial occlusion must be promptly identified.
• DWI abnormalities not due to arterial occlusion will often not conform to an arterial territory.
• Several important non-ischaemic entities can present on DWI and should not be confused with infarct.
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