Original article
Serial brain MRI in TIA patients

https://doi.org/10.1016/j.neurad.2012.02.002Get rights and content

Summary

Objective

Up to 40% of patients with transient ischemic attack (TIA) demonstrate lesions on diffusion-weighted magnetic resonance imaging (DWI). However, the time course of these ischemic lesions is not well known. Some lesions could vanish soon after symptom onset whereas others could be visible only after a certain delay. Based on a population of TIA patients imaged twice with DWI within the first week after onset, our aim was to estimate the rate of patients with DWI reversible ischemic lesion or with delayed DWI positivity.

Methods

We retrospectively compared DWI at admission (DWI1, median = 15 hours after TIA) with follow-up DWI (DWI2, median = 47 hours) in 64 consecutive TIA over a 7-month period. DWI was reviewed in consensus by two readers, blinded to clinical information. Number, extent and arterial distribution of lesions were assessed.

Results

DWI1 and DWI2 showed similar findings in 55 TIA patients (32 with and 23 without ischemic lesions). In nine (14%) patients, changes were observed on DWI2: presence of ischemic lesions despite normal DWI1 (n = 3), increase in lesion size (n = 3), or partial or complete lesion reversibility (n = 3).

Conclusion

In most TIA cases, ischemic lesions captured by early DWI and 48-hour DWI are similar. However, some ischemic lesions vanish rapidly while lesion visibility is delayed in other cases.

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.

References (30)

  • Y. Terasawa et al.

    Reversible diffusion-weighted lesion in a TIA patient without arterial recanalization: a case report

    J Neurol Sci

    (2008)
  • J.D. Easton et al.

    Definition and evaluation of transient ischemic attack: a scientific statement for healthcare professionals from the American Heart Association/American Stroke Association Stroke Council; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; and the Interdisciplinary Council on Peripheral Vascular Disease. The American Academy of Neurology affirms the value of this statement as an educational tool for neurologists

    Stroke

    (2009)
  • S.T. Engelter et al.

    Diffusion MR imaging and transient ischemic attacks

    Stroke

    (1999)
  • B.L. Cucchiara et al.

    Is the ABCD score useful for risk stratification of patients with acute transient ischemic attack?

    Stroke

    (2006)
  • D. Calvet et al.

    DWI lesions and TIA etiology improve the prediction of stroke after TIA

    Stroke

    (2009)
  • S.T. Engelter et al.

    Optimizing the risk estimation after a transient ischaemic attack – the ABCDE plus sign in circle score

    Eur J Neurol

    (2012)
  • F.E. Lecouvet et al.

    Resolution of early diffusion-weighted and FLAIR MRI abnormalities in a patient with TIA

    Neurology

    (1999)
  • T. Neumann-Haefelin et al.

    Diffusion- and perfusion-weighted MRI in a patient with a prolonged reversible ischaemic neurological deficit

    Neuroradiology

    (2000)
  • C.S. Kidwell et al.

    Diffusion MRI in patients with transient ischemic attacks

    Stroke

    (1999)
  • C. Oppenheim et al.

    False-negative diffusion-weighted MR findings in acute ischemic stroke

    AJNR Am J Neuroradiol

    (2000)
  • W. Kuker et al.

    MRI characteristics of acute and subacute brainstem and thalamic infarctions: value of T2- and diffusion-weighted sequences

    J Neurol

    (2002)
  • G. Schlaug et al.

    Time course of the apparent diffusion coefficient (ADC) abnormality in human stroke

    Neurology

    (1997)
  • Y. Inatomi et al.

    Hyperacute diffusion-weighted imaging abnormalities in transient ischemic attack patients signify irreversible ischemic infarction

    Cerebrovasc Dis

    (2005)
  • M. Mlynash et al.

    Yield of combined perfusion and diffusion MR imaging in hemispheric TIA

    Neurology

    (2009)
  • S. Prabhakaran et al.

    Perfusion computed tomography in transient ischemic attack

    Arch Neurol

    (2011)
  • Cited by (12)

    • Detectability of ischemic lesions on diffusion-weighted imaging is biphasic after transient ischemic attack

      2015, Journal of Stroke and Cerebrovascular Diseases
      Citation 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.

    • An update on brain imaging in transient ischemic attack

      2015, Journal of Neuroradiology
      Citation 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.

    • Examination timing and lesion patterns in diffusion-weighted magnetic resonance imaging of patients with classically defined transient ischemic attack

      2013, Journal of Stroke and Cerebrovascular Diseases
      Citation 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.

    • Frequent inaccuracies in ABCD<sup>2</sup> scoring in non-stroke specialists' referrals to a daily Rapid Access Stroke Prevention service

      2013, Journal of the Neurological Sciences
      Citation 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.

    View all citing articles on Scopus
    View full text