Brain imaging in transient ischemic attack – redefining TIA

Recurrent migraine aura-like symptoms in an elderly woman: symptomatic cortical spreading depression?

Cortical spreading depression (CSD) has been directly observed in humans with malignant stroke, traumatic brain injury and subarachnoid haemorrhage and is also considered to be the correlate of migraine aura. We report on a 76-year-old woman with new-onset episodes of headache, paraesthesia, hemiparesis and dysarthria, in whom a small cortical subarachnoid haemorrhage was diagnosed with MRI. Repeated diffusion-weighted MRI scans shortly after transient focal neurological episodes as well as diagnostic workup were normal, which makes recurrent transient ischaemic attacks unlikely. Ictal electroencephalogram recordings showed no epileptic activity. Long-term follow-up revealed a diagnosis of probable cerebral amyloid angiopathy. We propose that CSD could be a pathophysiological correlate of transient focal neurological deficits in patients with cortical bleeding.

Incidence and Predictors of Acute Ischemic Lesions on Brain Magnetic Resonance Imaging in Patients With a Clinical Diagnosis of Transient Ischemic Attack in China

Background: The associations between the clinical characteristics and diffusion-weighted imaging (DWI) positivity in patients with a clinical diagnosis of transient ischemic attack (TIA) are still poorly understood. The purpose of our study was to determine the incidence of TIA related acute infarction by DWI, and to determine the underlying predictors of DWI positivity in TIA patients.

Methods: Between Jan 2017 and Dec 2018, we retrospectively enrolled 430 patients with a clinical diagnosis of TIA who underwent DWI. Patients were divided into those with acute ischemic lesions (DWI positive group) and those without (DWI negative group). The clinical characteristics, laboratory data, and imaging parameters were compared between the two groups.

Results: A total of 430 time-based TIA patients (mean age, 61.4 ± 13.0) were enrolled in this study. About 126 (29.3%) of TIA patients had a DWI positive lesion in our series. Comparing TIA patients with positive DWI to those with negative DWI, acute lesions were more likely to be more male, have higher hyperlipidemia and a smoking history, more speech abnormalities and increased motor weakness; and higher systolic and diastolic blood pressure, homocysteine, fasting blood glucose, and the scores of ABCD2, ABCD3, ABCD3-I, and Dawson. Several independent predictors of DWI positivity were identified with logistic regression analysis: motor weakness (odds ratio 4.861, P = 0.021), speech abnormalities (odds ratio 4.029, P = 0.024), and ABCD3-I (odds ratio 13.141, P = 0.001). ABCD3-I showed the greatest area under the ROC curve, with a sensitivity of 85.7% and specificity of 72.4%.

Conclusion: In patients with a clinical diagnosis of TIA, 29.3% demonstrated acute DWI lesions on brain magnetic resonance imaging (MRI). They were associated with motor weakness, speech abnormalities and higher ABCD3-I score at admission.

Oro-facial impairment in stroke patients

Stroke is considered one of the leading causes of death and acquired disability with a peak prevalence over the age of 80 years. Stroke may cause debilitating neurological deficiencies that frequently result in sensory deficits, motor impairment, muscular atrophy, cognitive deficits and psychosocial impairment. Oro-facial impairment may occur due to the frequent involvement of the cranial nerves' cortical representation areas, central nervous system pathways or motoneuron pools. The aim of this narrative, non-systematic review was to discuss the implications of stroke on oro-facial functions and oral health-related quality of life (OHRQoL). Stroke patients demonstrate an impaired masticatory performance, possibly due to reduced tongue forces and disturbed oral sensitivity. Furthermore, facial asymmetry is common, but mostly discrete and lip restraining forces are reduced. Bite force is not different between the ipsi- and contra-lesional side. In contrast, the contra-lesional handgrip strength and tongue-palate contact during swallowing are significantly impaired. OHRQoL is significantly reduced mainly because of the functional impairment. It can be concluded that impaired chewing efficiency, dysphagia, facial asymmetry, reduced lip force and OHRQoL are quantifiable symptoms of oro-facial impairment following a stroke. In the absence of functional rehabilitation, these symptoms seem not to improve. Furthermore, stroke affects the upper limb and the masseter muscle differently, both, at a functional and a morphological level. The rehabilitation of stroke survivors should, therefore, also seek to improve the strength and co-ordination of the oro-facial musculature. This would in turn help improve OHRQoL and the masticatory function, subsequently preventing weight loss and malnutrition.

Role of Diffusion-weighted Imaging in Acute Stroke Management using Low-field Magnetic Resonance Imaging in Resource-limited Settings

A variety of imaging modalities exist for the diagnosis of stroke. Several studies have been carried out to ascertain their contribution to the management of acute stroke and to compare the benefits and limitations of each modality. Diffusion-weighted imaging (DWI) has been described as the optimal imaging technique for diagnosing acute ischemic stroke, yet limited evidence is available on the value of DWI in the management of ischemic stroke with low-field magnetic resonance (MR) systems. Although high-field MR imaging (MRI) is desirable for DWI, low-field scanners provide an acceptable clinical compromise which is of importance to developing countries posed with the challenge of limited availability of high-field units. The purpose of this paper was to systematically review the literature on the usefulness of DWI in acute stroke management with low-field MRI scanners and present the experience in Nigeria.

Transient ischemic attacks: predictability of future ischemic stroke or transient ischemic attack events

The short-term risk of an ischemic stroke after a transient ischemic attack (TIA) is estimated to be approximately 3%–10% at 2 days, 5% at 7 days, and 9%–17% at 90 days, depending on active or passive ascertainment of ischemic stroke. Various risk prediction scores are available to identify high-risk patients. We present here a pragmatic review of the literature discussing the main scoring systems. We also provide the sensitivity, specificity, positive predictive value, and negative predictive value for each scoring system. Our review shows that scoring systems including brain imaging and vascular imaging are better at risk prediction than scores that do not include this information.

Clinical implications of increased use of MRI in TIA

BACKGROUND

Transient ischemic attack has been redefined as a tissue-based diagnosis and MRI recommended as the preferred imaging modality. We aimed to investigate whether an increased use of MRI leads to a decrease in the proportion of TIA as compared to cerebral infarction. We also sought to see whether DWI-positive patients with transient ischemic symptoms <24 h differ from DWI-negative TIA patients in terms of performed diagnostic investigations and clinical characteristics.

METHODS

Patients admitted with cerebral infarction or TIA in the period 2006-2011 were prospectively registered. The use of MRI in patients with transient ischemic symptoms <24 h and proportion of TIA were annually recorded. DWI-positive and DWI-negative patients with transient ischemic symptoms <24 h were compared in univariate analyses regarding baseline data, diagnostic investigations, and etiology. Multivariate analyses were performed to identify predictors of DWI lesions.

RESULTS

The use of MRI increased from 65.0% in 2006-2008 to 89.0% in 2009-2011 (P < 0.001). The proportion of TIA as compared to cerebral infarction decreased from 12.2% in 2006-2008 to 8.3% in 2009-2011 (P = 0.002). DWI-positive patients were more often examined with 24-h Holter monitoring (P < 0.001) and echocardiography (P < 0.001). Lower age (P < 0.001) and prior myocardial infarction (P < 0.029) were independently associated with DWI lesions in patients with transient ischemic symptoms <24 h.

CONCLUSIONS

An increased use of MRI and a tissue-based TIA definition resulted in a decrease in the proportion of TIA at discharge as compared to cerebral infarction. DWI-positive patients had a more extensive cardiac work-up and were associated with lower age and prior myocardial infarction.

Characterisation of endothelin-1-induced intrastriatal lesions within the juvenile and adult rat brain using MRI and 31P MRS

Improved non-invasive magnetic resonance (MR) characterisation of in vivo models of focal ischaemic insults such as transient ischaemic attack (TIA) and perinatal arterial ischaemic stroke (AIS) may assist diagnosis, outcome prediction and treatment design. The classic middle cerebral artery occlusion (MCAO) model of ischaemic stroke is well documented in MR studies but generates extensive and complex lesions involving an acute inflammatory response and de-occlusion that immediately restores circulation. By contrast, intrastriatal microinjection of the potent vasoconstrictor, endothelin-1 (ET-1), induces a focal, reversible and low-flow ischaemia in the absence of a typical inflammatory response, which gradually restores blood flow over several hours and may be more relevant to TIA and AIS pathology. This study presents the first comprehensive longitudinal MR characterisation of the real-time anatomical [T1-weighted (T1-w)/T2-weighted (T2-w)], pathophysiological [apparent diffusion coefficient (ADC), cerebral blood volume, gadolinium contrast imaging of blood-brain barrier (BBB) integrity] and metabolic [phosphorus magnetic resonance spectroscopy (31P MRS)] evolution of a purely ischaemic ET-1-induced lesion within the juvenile and adult rat brain. ET-1-induced cytotoxic oedema was visualised on T2-w magnetic resonance imaging (MRI), inconsistent with the conventional notion that it cannot be detected using anatomical MRI. There was no immunohistochemical evidence of an acute inflammatory response or loss of BBB integrity, thus excluding a vasogenic oedema contribution to the pathology. Maximal T2-w intensity correlated with the lowest ADC value in both age groups, re-emphasising the purely ischaemic nature of the lesion and the absence of vasogenic oedema. Furthermore, extensive acute T1-w hypointensity was observed in the presence of cytotoxic oedema-induced T2-w changes, whereas other authors have shown that increased T1 values following MCAO reflect vasogenic oedema. Intriguingly, the lesion border exhibited hyperintensity on T2-w and ADC MRI at later time points, and the former may be a consequence of phagocytosis-induced fatty droplet deposition by macrophages detected immunohistochemically. In spite of a chronically reduced ADC, typically associated with ischaemia-induced energy failure, a 31P MRS-detectable reduction in the phosphocreatine (PCr) to gamma adenosine triphosphate (γATP) ratio was not observed at any time point in either age group, suggesting dissociation of tissue water diffusion and metabolic changes within the ET-1-induced lesion.

Nuclear medicine in cerebrovascular disease

Stroke and cerebrovascular diseases are major causes of mortality, morbidity, and disability. Nuclear Medicine, primarily via tomographic methods, has made significant contributions to the understanding of the hemodynamic and metabolic consequences of cerebrovascular diseases. In this review, the findings in acute, subacute, and chronic cerebrovascular diseases are described. Many of the pathophysiologic processes and consequences that follow stroke, including completed infarct core, adjacent penumbra, and diaschisis, have been investigated with Nuclear Medicine, and stroke outcome may be related to these phenomena. Additional topics included in this review are cerebrovascular reserve tests and multi-infarct dementia. Finally, Nuclear Medicine investigations of stroke recovery and cerebral plasticity appear to indicate that enhanced activity of preexisting networks, rather than substitution of function, represents the most important mechanism of improvement in chronic stroke rehabilitation.