Diffusion-weighted echo-planar MRI of lacunar infarcts

Integrative Approaches in Acute Ischemic Stroke: From Symptom Recognition to Future Innovations

Among the high prevalence of cerebrovascular diseases nowadays, acute ischemic stroke stands out, representing a significant worldwide health issue with important socio-economic implications. Prompt diagnosis and intervention are important milestones for the management of this multifaceted pathology, making understanding the various stroke-onset symptoms crucial. A key role in acute ischemic stroke management is emphasizing the essential role of a multi-disciplinary team, therefore, increasing the efficiency of recognition and treatment. Neuroimaging and neuroradiology have evolved dramatically over the years, with multiple approaches that provide a higher understanding of the morphological aspects as well as timely recognition of cerebral artery occlusions for effective therapy planning. Regarding the treatment matter, the pharmacological approach, particularly fibrinolytic therapy, has its merits and challenges. Endovascular thrombectomy, a game-changer in stroke management, has witnessed significant advances, with technologies like stent retrievers and aspiration catheters playing pivotal roles. For select patients, combining pharmacological and endovascular strategies offers evidence-backed benefits. The aim of our comprehensive study on acute ischemic stroke is to efficiently compare the current therapies, recognize novel possibilities from the literature, and describe the state of the art in the interdisciplinary approach to acute ischemic stroke. As we aspire for holistic patient management, the emphasis is not just on medical intervention but also on physical therapy, mental health, and community engagement. The future holds promising innovations, with artificial intelligence poised to reshape stroke diagnostics and treatments. Bridging the gap between groundbreaking research and clinical practice remains a challenge, urging continuous collaboration and research.

The Potential Impact of Neuroimaging and Translational Research on the Clinical Management of Lacunar Stroke

Lacunar infarcts represent one of the most frequent subtypes of ischemic strokes and may represent the first recognizable manifestation of a progressive disease of the small perforating arteries, capillaries, and venules of the brain, defined as cerebral small vessel disease. The pathophysiological mechanisms leading to a perforating artery occlusion are multiple and still not completely defined, due to spatial resolution issues in neuroimaging, sparsity of pathological studies, and lack of valid experimental models. Recent advances in the endovascular treatment of large vessel occlusion may have diverted attention from the management of patients with small vessel occlusions, often excluded from clinical trials of acute therapy and secondary prevention. However, patients with a lacunar stroke benefit from early diagnosis, reperfusion therapy, and secondary prevention measures. In addition, there are new developments in the knowledge of this entity that suggest potential benefits of thrombolysis in an extended time window in selected patients, as well as novel therapeutic approaches targeting different pathophysiological mechanisms involved in small vessel disease. This review offers a comprehensive update in lacunar stroke pathophysiology and clinical perspective for managing lacunar strokes, in light of the latest insights from imaging and translational studies.

New concepts in lacunar stroke etiology: the constellation of small-vessel arterial disease

OBJECTIVE

To update the less frequent etiologies causing lacunar infarcts (LIs). To highlight recent advances in risk factors, clinical syndromes, topography, complementary tests and long-term prognosis in this subtype of ischemic stroke.

PATIENTS AND METHODS

The most important studies are analyzed, from CM Fisher works, selecting those referring to LIs of unusual etiology, and recent advances and controversies in the clinical management of LI are discussed.

RESULTS

LIs are found in approximately 11% of patients admitted with stroke. The pure motor hemiparesis (55%) constitutes the most usual lacunar syndrome. However, lacunar syndromes may not be caused by LIs in 10-20% of cases. LIs caused by microembolism and cholesterol embolism from the aortic arch are reviewed. Hematological diseases can also cause LI, such as polycythemia rubra vera, essential thrombocythemia and primary antiphospholipidic antibody syndrome. Other etiologies are carotid plaque embolism, severe stenosis of a perforated arteriole and amyloid angiopathy. Infectious arteritis by neurolues, neurocysticercosis, neuroborreliosis, by AIDS or Helicobacter pylori infection have also been associated with the presence of LIs. Likewise, inflammatory arteritis in systemic lupus erythematosus or granulomatous angiitis, cocaine abuse and panarteritis nodosa have been related to LI, although in the latter LI would be caused by a thrombotic microangiopathy and not by vasculitis.

CONCLUSIONS

LI is an ischemic stroke subtype with a characteristic clinical presentation and a short-term favorable prognosis. Although high blood pressure constitutes the main risk factor and the main etiology, LIs may be caused, in less than 5% of cases, by various etiologies, mainly hematological diseases and infectious or inflammatory arteritis. It is essential to make a correct etiological diagnosis for LI as treatment will be different according to its etiology.

Diffusion-Weighted MRI Findings in Patients with Capsular Warning Syndrome

BACKGROUND AND PURPOSE

The 'capsular warning syndrome' (CWS) of recurrent stereotyped episodes of motor or sensory dysfunction is clinically well recognized, and is associated with a high risk of imminent lacunar infarction with permanent deficits resembling those of CWS. However, the pathophysiology of CWS has not been well characterized. We report a clinicoanatomic correlation with MR imaging studies in the acute and chronic phases in patients with CWS.

MATERIAL AND METHODS

Between April 1997 and March 2001, we prospectively studied 8 patients, mean age 73.3 years, presenting with 4-17 motor or sensorimotor transient ischemic attacks (TIAs; duration 2-90 min) up to 3 days after onset of the first episode. Four patients were free of symptoms between the attacks and had no residua, whereas 4 patients developed a pure motor or sensorimotor stroke within 1-3 days after symptom onset. Diffusion-weighted echoplanar MRI (DWI) and T(2)-weighted MRI studies were performed within 1 week after symptom onset and were repeated 1-2 months later.

RESULTS

Seven of the 8 patients had an appropriate lesion on DWI in the acute phase. DWI abnormalities in the 3 patients with TIAs were 4-10 mm in diameter and confined to the lateral thalamus or medial globus pallidus without involving the internal capsule, whereas 4 patients who developed a stroke had abnormalities localized to the putamen extending to corona radiata (3 patients), or the pontomesencephalic junction (1 patient). All 6 patients who underwent follow-up MRI had an infarct on T(2)-weighted images corresponding to, but usually smaller than, the acute phase DWI abnormality.

CONCLUSIONS

Small infarcts in the basal ganglia or the pons, close to central motor pathways, appear to be the primary lesion in CWS. The pathophysiology of CWS is complex, and may involve hemodynamic mechanisms in penetrating arterial territories, as well as molecular mechanisms, such as peri-infarct depolarizations affecting adjacent motor pathways.

Clinical diagnosis of subcortical cerebral infarction

Clinical diagnosis of subcortical infarction, chiefly lacunar stroke, has been considered important for arriving at the most rational stroke diagnosis and treatment strategy. This review focuses on the lacunar hypothesis and potential inaccuracy of clinical diagnosis and computed tomography in subcortical stroke. Modern magnetic resonance imaging techniques have increased sensitivity and specificity for subcortical infarcts and may help in determining the pathogenesis in individual patients. Full investigation is now favored for all stroke patients regardless of the clinical diagnosis. Acute stroke and secondary prevention treatments are discussed in reference to a diagnosis of subcortical infarction.

Long-term prognosis after lacunar infarction

Lacunar infarcts, small deep infarcts that result from occlusion of a penetrating artery, account for about a quarter of all ischaemic strokes. These infarcts have commonly been regarded as benign vascular lesions with a favourable long-term prognosis. However, recent studies have shown that this is only the case early in the disease course. A few years after infarct, there is an increased risk of death, mainly from cardiovascular causes. The risk of recurrent stroke after lacunar infarct is similar to that for most other types of stroke, and patients have an increased risk of developing cognitive decline and dementia. Age, vascular risk factors, high nocturnal blood pressure, and severity of cerebral small-vessel disease at onset have significant prognostic implications for almost all outcomes. More studies on mechanisms, prevention, and treatment are needed to provide specific guidance on the long-term management of patients with lacunar infarcts. Risk-factor modification is likely to play a large part in therapeutic interventions targeted at this stroke subtype.

The imaging of ischaemic stroke

Stroke is a clinical syndrome of a rapidly developing focal neurological deficit that may be classified for practical purposes into ischaemic and haemorrhagic. The role of imaging is to exclude mimics of ischaemic stroke or intracranial haemorrhage and confirm the presence of an ischaemic stroke. Computed tomography (CT) remains the investigation of choice to exclude acute intracranial haemorrhage but diffusion weighted magnetic resonance (MR) has proved to be a sensitive method of detecting early ischaemic infarction. Perfusion weighted MR allows further assessment at the same examination that could help guide the clinician in the risk/benefit analysis of treatment with thrombolytics or neuroprotective agents under evaluation. This can also be achieved with CT. This review article discusses the imaging of ischaemic stroke, relating the pathophysiology of stroke to it. It deals separately in more detail with these newer MR techniques.

Systematic review of diffusion and perfusion imaging in acute ischemic stroke

BACKGROUND AND PURPOSE

Recent advances in neuroimaging have raised hopes of early and accurate identification of ischemic brain and the discrimination of dead from salvageable tissue. We sought to determine whether the data published so far are enough to establish the roles of these techniques in everyday clinical practice.

METHODS

A systematic review of studies of MR diffusion-weighted imaging (DWI), perfusion imaging (PI), or a combination of the two, in human stroke, excluding abstracts and case reports. One reviewer extracted information on the size of each study, its main purpose, methodological details, and results.

RESULTS

We identified 47 studies of DWI, 18 studies of MR PI alone or in combination with another advanced imaging modality, and 19 studies of DWI and PI together. Although high proportions of the studies were prospective and gave good details of the imaging sequences used, the majority gave very limited details on patient selection and clinical characteristics or blinded imaging assessment. Pathophysiological changes were inferred from DWI/PI patterns that were not supported by other data.

CONCLUSIONS

Despite considerable enthusiasm for and promise of these techniques, there is not sufficient information available in these studies to enable us to draw firm conclusions about the sensitivity and specificity of these techniques for identification of either ischemic lesions not visible by other means or salvageable tissue. Future studies should include larger numbers of carefully described patients, assess the contribution of DWI over and above other imaging, obtain follow-up at an appropriate time interval to determine accurate clinical and neuroradiological outcomes, and assess DWI/PI abnormality with reperfusion in randomized treatment trials. Investigators should also be encouraged to combine their individual patient data in meta-analyses to obtain a more robust assessment of the value of DWI and PI from larger sample sizes.

Impact on stroke subtype diagnosis of early diffusion-weighted magnetic resonance imaging and magnetic resonance angiography

BACKGROUND AND PURPOSE

The purpose of the present study was to assess the diagnostic usefulness of early diffusion-weighted MRI (DWI) and MR angiography (MRA) in patients with ischemic stroke. Past approaches to stroke diagnosis required a series of diagnostic tests over several days of hospitalization. New magnetic resonance methodologies that include DWI and MRA may allow more rapid characterization of stroke pathophysiology. However, no previous study has assessed the impact on formal stroke subtype diagnosis of early imaging with DWI/MRA.

METHODS

We analyzed 46 consecutive patients with acute ischemic stroke who underwent DWI/MRA within 24 hours of admission. Initial diagnoses were rendered with use of the 2 most widely used formal stroke subtype classification schemes, the TOAST and the Oxfordshire methods, which were applied to patients after CT/conventional MRI but before DWI/MRA. Modified TOAST and Oxfordshire diagnoses were then rendered based on the results of day 1 DWI, MRA, and DWI plus MRA. Final TOAST/Oxfordshire diagnoses at discharge were taken as the gold standard.

RESULTS

Compared with final diagnoses, pre-MRI TOAST diagnoses matched final diagnoses in 48%, improving to 83% after DWI alone, 56% after MRA alone, and 94% after DWI plus MRA. For the TOAST diagnostic subtypes of large-vessel atherothromboembolism and small-vessel disease, pre-MRI diagnoses matched final diagnoses in 56% and 35% of patients, respectively, improving to 89% and 100% after DWI/MRA. Pre-MRI Oxfordshire diagnoses matched final diagnoses in 67% of patients, improving to 100% after DWI.

CONCLUSIONS

The use of DWI/MRA within 24 hours of hospitalization substantially improves the accuracy of the diagnosis of early ischemic stroke subtype. When initial management and clinical trial eligibility decisions are influenced by stroke subtype, day 1 multimodal MRI is advantageous as a guide to therapy.

MR imaging evaluation of seizures

It is imperative for a radiologist to determine the type of seizure a patient has prior to magnetic resonance (MR) imaging to optimally provide the clinician with the information he or she requires. Specifically, complex partial seizures require evaluation of the frontal lobes and the hippocampus (for mesial temporal sclerosis). These are best evaluated with fluid-attenuated inversion recovery (FLAIR) imaging; the use of intravenously administered contrast material is not required. Other types of chronic seizures are best evaluated with nonenhanced FLAIR or T2-weighted imaging for low-grade tumors, vascular malformations, gliosis after infarction, inflammation, or trauma. The presence of new-onset seizures in an adult or the worsening of chronic seizures warrants T2-weighted or FLAIR imaging and gadolinium-enhanced T1-weighted imaging (to look for primary or metastatic tumors, infections, or inflammatory lesions). If available, echo-planar diffusion imaging should be used also (to look for acute infarcts).