Magnetic resonance imaging of arterial stroke mimics: a pictorial review

Abstract

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.

Role of 3D Pseudocontinuous Arterial Spin-Labeling Perfusion in the Diagnosis and Follow-Up in Patients with Herpes Simplex Encephalitis

“…Neuroimaging examinations may demonstrate characteristic findings of HSE and are of great importance in the differential diagnosis. As reported in the literature, 5,11,24 our results also demonstrated that the lesions on conventional MR imaging manifest as an asymmetric involvement of the temporal lobes. Other brain regions, such as frontal lobes, insular lobes, hippocampus region, and cingulate cortex, might also be affected, while the basal ganglia region and cerebellum are rarely involved.…”

“…Other brain regions, such as frontal lobes, insular lobes, hippocampus region, and cingulate cortex, might also be affected, while the basal ganglia region and cerebellum are rarely involved. 24 Routine MR images including T1WI, T2WI, T2 FLAIR, DWI, and postcontrast images are most important in identifying brain abnormalities in HSE. Perfusion imaging has been widely applied in research and clinical practice to provide more information in various neurologic disorders.…”

Stroke mimics: incidence, aetiology, clinical features and treatment

“…The diagnosis is particularly difficult if it is the first attack of MS. While CT may be normal, MRI will show white matter lesions in typical locations and often additional asymptomatic lesions [ 20 ]. It is important to remember that the event may be an acute stroke in a patient with MS.…”

Case 26-2020: A 60-Year-Old Woman with Altered Mental Status and Weakness on the Left Side

“…Brain lesions with restricted diffusion typically indicate stroke, but given this patient’s presentation, I will consider a broader differential diagnosis. 18 Encephalitic and demyelinating lesions can have restricted diffusion, and demyelination has been reported in association with Covid-19–related encephalitis. 6 , 14 , 19 However, demyelinating lesions are usually patchy and associated with leptomeningeal enhancement and moderate-to-severe respiratory illness, characteristics that are not consistent with those seen in this patient.…”