Research Article: Refinement of Imaging Predictors of Recurrent Events following Transient Ischemic Attack and Minor Stroke

Date Published: June 21, 2013

Publisher: Public Library of Science

Author(s): Myles Horton, Jayesh Modi, Shiel K. Patel, Andrew M. Demchuk, Mayank Goyal, Michael D. Hill, Shelagh B. Coutts, Jean-Claude Baron. http://doi.org/10.1371/journal.pone.0065752

Abstract

TIA and minor stroke have a high risk of recurrent stroke. Abnormalities on CT/CTA and MRI predict recurrent events in TIA and minor stroke. However there are many other imaging abnormalities that could potentially predict outcome that have not been assessed in this population. Also the definition of recurrent events used includes deterioration due to stroke progression or recurrent stroke and whether imaging is either of these is not known.

To improve upon the clinical, CT/CTA and MRI parameters that predict recurrent events after TIA and minor stroke by assessing further imaging parameters. Secondary aim was to explore predictors of stroke progression versus recurrent stroke.

510 consecutive TIA and minor stroke patients had CT/CTA and most had MRI. Primary outcome was recurrent events (stroke progression or recurrent stroke) within 90 days. Further imaging parameters were assessed for prediction of recurrent events (combined outcome of stroke progression and recurrent stroke). We also explored predictors of symptom progression versus recurrence individually.

36 recurrent events (36/510, 7.1% (95% CI: 5.0–9.6)) including 19 progression and 17 recurrent strokes. On CT/CTA: white matter disease, prior stroke, aortic arch focal plaque≥4 mm, or intraluminal thrombus did not predict recurrent events (progression or recurrent stroke). On MRI: white matter disease, prior stroke, and microbleeds did not predict recurrent events. Parameters predicting the individual outcome of symptom progression included: ongoing symptoms at initial assessment, symptom fluctuation, intracranial occlusion, intracranial occlusion or stenosis, and the CT/CTA metric. No parameter was strongly predictive of a distinct recurrent stroke.

There was no imaging parameter that could improve upon our original CT/CTA or MRI metrics to predict the combined outcome of stroke progression or a recurrent stroke after TIA and minor stroke. We are better at using imaging to predict stroke progression rather than recurrent stroke.

Partial Text

Transient ischemic attacks (TIAs) and minor strokes carry a high-short term risk of recurrent stroke. Much previous work has been completed to determine the clinical and imaging factors that increase the risk of developing a disabling stroke following a TIA or minor stroke. There are several clinical and event related factors that increase the risk of stroke after TIA [1]. Imaging also plays a role in predicting outcomes in these patients [2]–[4].

Consecutive patients aged at least 18 years presenting with a high risk TIA focal weakness or speech disturbance lasting at least five minutes or minor ischemic stroke (NIHSS score of 3 or less) who were referred to the stroke team at Foothills Medical Centre, were prospectively considered for enrolment. Patients were examined by a stroke neurologist and had a CT brain and CTA of the circle of Willis and neck within 24 hours of symptoms onset. The majority of patients also had a stroke MRI performed. Exclusion criteria included acute treatment with a thrombolytic drug, pre-morbid mRS of 2 or greater, and the presence of a serious co-morbid illness that would likely result in death within three months. The local ethics committee – The Calgary Health Research Ethics Board – associated with the Foothills Medical Centre and the University of Calgary approved this protocol and each patient provided written informed consent. Detailed baseline clinical and outcome data was collected for each participant. Above standard clinical data we sought to review the role of fluctuation in the prediction of recurrent events. Fluctuation was prospectively defined as having occurred if a patient deteriorated then improved on more than one occasion with symptoms referable to the same brain location. This was rated at the time of the initial physician neurological assessment and was based either on the clinical history or on clinical examination (if the patient was still fluctuating at the time of initial assessment). Fluctuation later than the time of initial assessment was not recorded. Any event that occurred more than 24 hours before the initial assessment was not considered in the assessment of fluctuation. Patients received routine clinical care including antihypertensive and lipid-lowering therapy at the discretion of the treating physician. Ongoing symptoms were assessed at the time of first assessment by the stroke neurology team in the emergency department. Ongoing symptoms were defined as the patient having any deficit measureable on the standard bedside neurological examination. All individuals were trained in the neurological examination and were completed by either a stroke neurologist or stroke fellow.

Five hundred ten patients were enrolled into the study during a period of 29 months. Follow up information was available in 98% (499/510). Baseline demographics are shown in Table 1. Four hundred twenty (82%) patients received an MRI for their initial event and 243 of these were DWI-positive (58%; 95% CI, 53–63). There were 36 recurrent events (7.1%; 95% CI, 5.0–9.6). Of these, 19 events were progression and 17 were recurrent strokes. Median time to recurrent event was 1 day (IQR 7.5).

We were not able to refine or improve upon the imaging predictors for recurrent events identified in the original CATCH paper. We did however find that the presence of symptom fluctuation was predictive of recurrent events. In the multivariable model this was additive to the CT/CTA metric in the prediction of recurrent events. In our exploratory analysis of separate predictors of symptom progression and recurrence, we found that imaging was much more predictive of progression than recurrence.

Source:

http://doi.org/10.1371/journal.pone.0065752