Original articleSerial brain MRI in TIA patients
Introduction
Because Diffusion-weighted Imaging (DWI) provides a precise evaluation of ischemic lesions in transient ischemic attack (TIA) patients, magnetic resonance imaging (MRI) is now recommended for the diagnostic work-up of patients with recent transient (< 24 hours) neurological symptoms. In these patients, the aggregate rate of DWI positivity is around 40% [1], with prevalence ranging from 25 to 67%. In TIA patients, a positive DWI confirms the vascular origin of symptoms, may guide the etiological work-up when lesions are distributed in distinct arterial territories [2] and importantly, has an independent prognostic value on the early risk of stroke recurrence [3], [4], [5]. However, DWI remains normal in up to 60% of patients who are clinically suspected of TIA. The time course of ischemic lesions in TIA patients is largely unknown. The variability in the delay from onset-to-MRI in TIA patients may account for the variability of the prevalence of DWI positivity between groups. As for stroke patients, lesions associated with TIA may be undetectable early after onset because of small lesion size or mild decrease in the apparent diffusion coefficient (ADC) values. In such cases, the lesion visibility may be delayed. Conversely, the DWI lesion may be reversible and vanish before MRI, as shown in several TIA cases studies [6], [7], [8]. Based on a population of TIA patients imaged twice with brain DWI within the first week after onset, our aim was to estimate the rate of patients with delayed DWI positivity or with DWI reversible ischemic lesion.
Section snippets
Subjects and methods
This retrospective study was carried on 127 consecutive patients admitted to our stroke unit during a 7-month period (March to September 2009) who received a final diagnosis of TIA. TIA was defined as a sudden, focal deficit of presumed vascular origin lasting less than 24 hours. For the purpose of this study, we identified from this population all patients who had two DWI sequences within 7 days after the onset of symptoms. Indeed, in our institution, TIA patients admitted to the stroke unit
Statistical analysis
To search for potential selection bias, we first compared the characteristics (age, sex ratio, positivity of DWI) of patients included in the study to that of excluded patients using a Chi2, a Student T or Mann-Whitney U test, where appropriate. Level of significance was set at P < 0.05. All quantitative data are described as mean ± standard deviation (SD), unless specified.
Results
The population initially consisted in 127 patients (age = 66.3 ± 15.1, 62 females) including 40 (31.5%) with a positive DWI (DWI1 and/or DWI2). There was no difference for sex, age, symptoms duration or delay from onset-to-DWI1. However, these groups significantly (P < 0.01) differed for the rate of DWI positivity, which was higher in the studied population (n = 32/64, 50%) than among the excluded patients (8/63, 12.7%).
In the 64 patients of the studied population (age, mean ± SD: 66.4 ± 15.6, 28 females),
Discussion
The main results of this retrospective study carried on 64 TIAs are the following: in 14% of TIAs, changes are observed on two serial DWI, with DWI lesion regression in 5% and DWI positivation in 10% of patients with initially normal DWI. This confirms that in TIA patients, an early DWI may miss an ischemic lesion, as previously shown for patient with persistent neurological symptoms [10]. As for stroke patients, all false-negative cases we observed were small and imaged within the first 24
Disclosure of interest
The authors declare that they have no conflicts of interest concerning this article.
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2015, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :In contrast, DWI findings in TIA are considerably different from those in cerebral infarction. DWI abnormalities observed in the hyperacute phase of TIA often resolve later.13,14 The reasons for disappearance of ischemic lesions in TIA patients have not yet been completely elucidated.
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2015, Journal of NeuroradiologyCitation Excerpt :Serial MR studies have shown that some ischemic lesions vanish rapidly and may no longer be visible 48 hours after TIA onset suggesting that delayed MRI after TIA reduces the diagnostic yield [33,34]. Conversely, lesion visibility is delayed in other cases [34,35], so the rate of DWI positivity might be underestimated if the first MRI is performed soon after the onset of symptoms (Fig. 9) [9]. Better understanding of the time course of DWI lesions after TIA may help improving the accuracy of brain MRI.
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2013, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :Second, there was a selection bias in this study for subjects who were TIA patients admitted to stroke-specialized hospitals, and the decisions of the hospitalization and management of TIA patients were made by individual attending physicians. Third, TIA patients with DWI lesions on initial MRI were not always examined by follow-up MRI, although the reversibility of DWI lesions in acute TIA patients was reported in previous studies.15,29,30 Fourth, DWI was not performed sequentially, but performed at skewed time points (81.7% within 24 hours from symptom onset) reflecting the retrospective nature of this study.
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2013, Journal of the Neurological SciencesCitation Excerpt :The ‘gold standard’ for TIA diagnosis in this study was the clinical diagnosis reached by an experienced vascular neurologist or stroke physician in the RASP clinic. Diffusion-weighted (DW) MRI was not obtained routinely in all patients, but ‘DWI-positivity’ is not the ‘gold standard’ for TIA diagnosis either, because only 33% to 49% of confirmed TIAs had an abnormal DWI in prior series [11,22–27]. Although additional variables, including imaging evidence of carotid stenosis or recent infarction on MRI may significantly improve risk stratification in secondary care, a ‘low-tech,’ easily applicable risk-stratification system is still relevant to primary care and economically disadvantaged settings, where access to the relevant investigations is limited or non-existent.