The Addition of MRI to CT Based Stroke and TIA Evaluation Does Not Impact One year Outcomes



Hebah Hefzy*, Elizabeth Neil, Patricia Penstone, Meredith Mahan, Panayiotis Mitsias , Brian Silver
Henry Ford Hospital, 2799 W. Grand Blvd. Detroit MI 48202, USA


Article Metrics

CrossRef Citations:
1
Total Statistics:

Full-Text HTML Views: 293
Abstract HTML Views: 265
PDF Downloads: 70
Total Views/Downloads: 628
Unique Statistics:

Full-Text HTML Views: 180
Abstract HTML Views: 159
PDF Downloads: 52
Total Views/Downloads: 391



© Hefzy et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Henry Ford Hospital, 2799 W. Grand Blvd. Detroit MI 48202, USA; Tel: 313-916-3014; Fax: 313-916-9107; E-mail: hhefzy1@hfhs.org


Abstract

Background:

The 2010 American Academy of Neurology guideline for the diagnosis of acute ischemic stroke recommends MRI with diffusion weighted imaging (DWI) over noncontrast head CT. No studies have evaluated the influence of imaging choice on patient outcome. We sought to evaluate the variables that influenced one-year outcomes of stroke and TIA patients, including the type of imaging utilized.

Methods:

Patients were identified from a prospectively collected stroke and TIA database at a single primary stroke center during a one-year period. Data were abstracted from patient electronic medical records. The primary outcome measure was death, myocardial infarction, or recurrent stroke within the following year. Secondary outcome measures included predictors of getting an MRI study.

Results:

727 consecutive patients with a discharge diagnosis of stroke or TIA were identified (616 and 111 respectively); 536 had CT and MRI, 161 had CT alone, 29 had MRI alone, and one had no neuroimaging. On multiple logistic regression analysis, there were no differences in primary or secondary outcome measures among different imaging strategies. Predictors of the primary outcome measure included age and NIHSS, while performance of a CT angiogram (CTA) predicted a decreased odds of death, stroke, or MI. The strongest predictor of having an MRI was admission to a stroke unit.

Conclusions:

These results suggest that long-term (one-year) patient outcomes may not be influenced by imaging strategy. Performance of a CTA was protective in this cohort. A randomized trial of different imaging modalities should be considered.

Keywords: : Imaging modality, Outcomes, Stroke, MRI, CT.



INTRODUCTION

The 2010 evidence-based guideline on The Role of Diffusion and Perfusion MRI for the Diagnosis of Acute Ischemic Stroke from the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology states that “diffusion-weighted imaging” (DWI) is established as useful and should be considered more useful than noncontrast CT for the diagnosis of acute ischemic stroke within 12 hours of symptom onset”[1]. The 2007 American Stroke Association Stroke Guidelines for the Early Management of Adults With Ischemic Stroke recommendations state that “in most instances, CT will provide the information to make decisions about emergency management” and that “multimodal CT and MRI may provide additional information that will improve diagnosis of ischemic stroke”[2]. The 2009 American Stroke Association Guidelines for the Definition and Evaluation of Transient Ischemic Attack state that “patients with TIA should preferably undergo neuroimaging evaluation within 24 hours of symptom onset. MRI, including DWI, is the preferred brain diagnostic imaging modality. If MRI is not available, head CT should be performed” [3].

Cost based studies looking at direct hospital cost of acute stroke care indicate that patients with more severe strokes incur the greatest hospital costs [4]. This is likely related to the additional cost of tests and procedures. Access to MRI scanners is often limited and MRI images typically become available at a time point in patient care where management decisions have already been made.

The preference for MRI over CT recommended or implied in these guidelines is based primarily on literature showing that MRI is more accurate for the diagnosis of acute cerebral injury in patients with new and sudden neurological change, whether the event lasts more or less than 24 hours [5,6]. In addition, MRI may be more sensitive than CT for the detection of acute hemorrhage [7]. However, CT is faster to obtain and more accessible than MRI, and contraindications to MRI were present in 45% of patients requiring urgent MRI in one study [8]. Preference for MRI over CT in octogenarians for the treatment of acute stroke does not show an improvement in outcome at three months [9]. To date, there have been no studies comparing diagnostic evaluation with or without MRI with respect to long-term patient outcome.

We sought to evaluate the outcomes of stroke and TIA patients evaluated and treated at a single tertiary care Primary Stroke Center [10]. The focus of the study was any potential association between imaging strategy and outcome at one year.

METHODS

This single center study was approved by the local institutional review board (IRB # 5867). Patients were identified from a prospectively collected database of stroke and TIA patients at a Primary Stroke Center. All patients admitted to Henry Ford Hospital between January 1, 2008 and Dec 31, 2008 with a discharge diagnosis of ischemic stroke or TIA were included. Data were abstracted from the prospectively collected database and from the patient electronic medical records. Variables that were recorded and whether that information was collected prospectively from the database or retrospectively from the chart review are noted in Table 1. Patient outcomes up to one year following admission were recorded. The primary outcome measure was death, myocardial infarction, or recurrent stroke within one year. Secondary outcome measures were stroke within one year, myocardial infarction within one year, death within one year, and predictors of an MRI occurring during a hospitalization.

Table 1.

Variables Collected


Clinical Data:

Length of stay
Age
Sex
Race
Atrial fibrillation (pre-existing or current)
History of congestive heart failure
History of stroke or TIA
History of coronary artery disease
History of diabetes mellitus
History of hypertension
History of peripheral vascular disease
Tobacco use within the previous year
History of carotid stenosis
History of dyslipidemia
History of prosthetic valve
Treatment with tPA
Median NIHSS at admission, discharge, first follow-up visit, and at 1 year
Median mRS at discharge

Labwork:

Cholesterol
Triglycerides
HDL
LDL

Diagnostic Studies:

CT head
MRI brain
CT Angiogram head/neck
MR Angiogram head/neck
Digital subtraction angiography
Carotid Ultrasonography
Transcranial Doppler
Transthoracic or transesophageal echocardiography

TIA = Transient Ischemic Attack, TPA = tissue plasminogen activator, NIHSS = National Institutes of Health Stroke Scale, mRS = Modified Rankin Score, HDL = high density lipoprotein, LDL = low density lipoprotein, CT = Computed Tomography, MRI = Magnetic Resonance Imaging

Univariate analyses using Chi-square and Fisher’s exact tests were performed for each outcome measure, and multivariable analysis was performed to adjust for any variable which trended towards significance (p < 0.1) on univariate analysis including age, median NIHSS score on admission, atrial fibrillation, and vascular risk factors (diabetes mellitus [DM], hypertension, coronary artery disease [CAD], and hyperlipidemia).

RESULTS

Between January 1, 2008 and December 31, 2008, 727 patients were discharged with a diagnosis of stroke or TIA. One patient with TIA did not h ave any neuroimaging and was excluded from further analysis. Of the remaining patients, 161 had CT alone, 29 had MRI alone, and 536 had CT and MRI. Of these patients, 616 had a diagnosis of stroke and 110 had a diagnosis of TIA. Baseline characteristics of patients with CT only and CT with MRI based evaluations are shown in Table 2. Among other differences, CT only patients were significantly older and had higher median NIHSS scores at admission.

Table 2.

Baseline Characteristics of Patients with CT only Versus CT with MRI Evaluations


Variable CT only (n=161) CT with MRI (n = 536) p-value
Age 71.1 +/- 15.8 65.7 +/- 13.8 <0.001
Female 50% 51% 0.956
Race (Black) 58% 66% 0.083
 (White) 39% 30%
Diabetes Mellitus 35% 35% 0.985
Atrial Fibrillation (pre-existing or current) 26% 8% <0.001
History of hypertension 79% 80% 0.749
Tobacco use within the previous year 14% 27% 0.001
History of stroke or TIA 26% 24% 0.672
History of coronary artery disease 29% 17% 0.001
History of congestive heart failure 29% 9% <0.001
History of carotid stenosis 2% 2% 0.722
History of dyslipidemia 30% 37% 0.141
Length of stay (days) 6.5 +/- 6.0 4.4 +/- 3.9 <0.001
History of peripheral vascular disease 3% 0% 0.011
History of prosthetic valve 4% 0% <0.001
Treatment with tPA 9% 7% 0.307
Median NIHSS score at admission 7 3 <0.001
Median NIHSS score at discharge 4 2 <0.001
Median NIHSS score at first follow-up visit 9 3 <0.001
Median NIHSS score at 1 year 0 0 0.975
Median mRS score at discharge 4 2 <0.001
Total cholesterol at admission (g/dl) 155 171 <0.001
Triglycerides at admission (g/dl) 105 121 0.002
HDL at admission (g/dl) 41 40 0.764
LDL at admission (g/dl) 94 107 <0.001
CTA head and neck 27% 17% 0.009
MRA head and neck 0% 90% <0.001
Digital subtraction angiography 8% 5% 0.202
Carotid ultrasonography 49% 21% <0.001
Transcranial doppler 28% 4% <0.001
Transthoracic/transesophageal echocardiography 82% 93% <0.001

NIHSS = National Institutes of Health Stroke Scale, mRS = modified Rankin scale

There were 122 deaths, 49 recurrent strokes, and 22 myocardial infarctions within one year of follow-up. Predictors of the primary outcome were age, admission NIHSS, and history of CAD, while performance of a CTA had the opposite effect (OR 0.473, 95% CI 0.262-0.854, p=0.0131). (Table 3). No other diagnostic study, including any MRI modality, had a significant effect on the primary outcome measure.

Table 3.

Multiple Logistic Regression Results for the Primary Outcome Measure (Stroke, Myocardial Infarction, or Death) Within One Year


Variable Odds Ratio 95% Confidence Interval P-Value
Age 1.031 1.016, 1.046 <0.0001
NIHSS on admission 1.104 1.073, 1.136 <0.0001
History of CAD 1.577 1.005, 2.474 0.0474
History of DM 1.464 0.987, 2.171 0.0580
History of atrial fibrillation 1.540 0.884, 2.684 0.1272
CT only 1.914 0.510, 7.187 0.3360
CT and MRI/MRA 1.519 0.494, 4.670 0.4659
CTA 0.473 0.262, 0.854 0.0131
MRA 0.767 0.361, 1.629 0.4899
TCD 0.720 0.369, 1.406 0.3363

NIHSS= National Institutes of Health Stroke Scale, CAD = coronary artery disease, DM = diabetes mellitus, MRA = magnetic resonance angiography, CTA = CT angiography, TCD = transcranial Doppler.

Adjustments were made for age, median NIHSS score at admission, atrial fibrillation, diabetes mellitus, hypertension, coronary artery disease, and hyperlipidemia. Results in italics are statistically significant.

For secondary outcome measures, on multivariate analysis, predictors of death included age (OR 1.048, 95% CI 1.028 1.067, p<0.0001), admission NIHSS (OR 1.132, 95% CI 1.096-1.168, p<0.0001), and presence of atrial fibrillation (OR for absence vs. presence = 0.516, 95% CI 0.280 – 0.950, p = 0.0337), while performance of a CTA was protective (OR 0.365, 95% CI 0.173-0.773, p=0.0085) (Table 4). The primary predictor of stroke and MI was a history of CAD (OR of absence vs. presence = 0.473, 95% CI 0.245-0.913, p= 0.0256 and 0.316, 95% CI 0.132 – 0.754, p = 0.0095 respectively).

Table 4.

Multiple Logistic Regression Results for Death Within One Year


Variable Odds Ratio 95% Confidence Interval P-Value
Age 1.048 1.028, 1.067 <0.0001
NIHSS on admission 1.134 1.098, 1.171 <0.0001
History of CAD 1.104 0.629, 1.936 0.7311
Atrial fibrillation 1.954 1.058, 3.611 0.0324
CT only 2.413 0.436, 13.366 0.3133
CT and MRI/MRA 1.613 0.341, 7.623 0.5466
CTA 0.365 0.173, 0.773 0.0085
MRA 0.468 0.192, 1.141 0.0950
Echocardiography 1.322 0.624, 2.799 0.4663
TCD 0.778 0.362, 1.672 0.5206

NIHSS= National Institutes of Health Stroke Scale, CAD = coronary artery disease, MRA = magnetic resonance angiography, CTA = CT angiography, TCD = transcranial Doppler.

Adjustments were made for age, median NIHSS score at admission, atrial fibrillation, diabetes mellitus, hypertension, coronary artery disease, and hyperlipidemia. Results in italics are statistically significant.

The odds of having MRI added to a CT based workup was evaluated after adjusting for previously reported variables and the greatest predictor of having an MRI was admission to a stroke unit (OR 6.0, 95% CI 3.486- 10.325, p <0.0001) (Table 5).

Table 5.

Predictors of Having MRI in Addition to CT


Variable Odds Ratio 95% Confidence Interval P-Value
Admission to stroke unit 6.0 3.486, 10.325 <0.0001
History of heart failure 0.264 0.146, 0.478 <0.0001
Triglycerides 1.004 1.000, 1.007 0.0365
CTA 0.347 0.205, 0.586 <0.0001
Carotid ultrasonography 0.357 0.219, 0.584 <0.0001
TCD 0.107 0.055, 0.211 <0.0001

CTA = CT angiography, TCD = transcranial Doppler.

Adjustments were made for age, median NIHSS score at admission, atrial fibrillation, diabetes mellitus, hypertension, coronary artery disease, and hyperlipidemia. Results in italics are statistically significant.

DISCUSSION

The introduction of CT technology for the imaging of the human brain in the early 1970s led to a dramatic change in the diagnosis of stroke [11]. Landmark clinical trials such as the NINDS rt-PA stroke trial [12] and ECASS III [13] would not have been safe to perform with CT imaging because of the approximately 13% of patients who have hemorrhagic stroke as the etiology of their symptoms [14]. MRI technology for human brain imaging was introduced in the early 1980s [15] and diffusion-weighted imaging (DWI)/perfusion imaging for evaluation of acute stroke were introduced in the 1990s [16].

MRI-based evaluations can improve short-term (i.e. 90-day) prognostication of stroke outcome when added to clinical information [17]. The RRE-90 scoring system, based on an analysis of 1,458 consecutive ischemic stroke patients, demonstrated an area under the ROC curve (AUC) of 0.70-0.80. CT-based evaluations also improve short-term (i.e. 90-day) prognostication after TIA [18]. The ABCD(2)I scoring system, based on an analysis of 4,574 patients , demonstrated an AUC of 0.72-0.85. Even clinically based scoring systems such as the Essen Stroke Risk Score (AUC of 0.59 for 1-year risk of recurrent stroke) [19] and the Stroke Prognosis Instrument II (AUC of 0.63 for 2-year risk of recurrent stroke or death) [20] have reasonable prognostic values. At this time, there are no studies to show the additional value of neuroimaging, in addition to clinical variables, for prognosis beyond 90 days. Furthermore, increasing refinement of prognostication of stroke risk with atrial fibrillation, reflected in the new CHA2DS2-VASc score, do not include any neuroimging variables yet show impressive 10-year risk predictions (C statistic of 0.888) [21].

In this single center study of stroke and TIA patients, the addition of MRI to a CT based work-up was not associated with improved patient outcomes up to one year following discharge. Direct comparison of patients with CT based workup to MRI only workup was not possible due to the very small number of patients who had MRI alone. In this cohort, performance of CTA was protective against the primary outcome and death. Previously, a multimodal approach utilizing both noncontrast head CT as well as CT angiography (CTA) with contrast of the head and neck has been shown to identify high risk transient ischemic attach (TIA) and minor stroke patients [22].

These findings may be a reflection of several factors. Patients admitted to Henry Ford Hospital with stroke receive treatments in accordance with Primary Stroke Center certification [10]. At this time, Primary Stroke Center certification requires compliance with eight measures (venous thromboembolism prophylaxis, discharged on antithrombotic therapy, anticoagulation therapy for atrial fibrillation/flutter, thrombolytic therapy, antithrombotic therapy by end of hospital day two, discharged on statin medication, stroke education, and assessed for rehabilitation) [23]. Previously, smoking cessation counseling and dysphagia screening were also included. These variables are known to influence outcome and are not dependent on the acquisition of MRI imaging. A second consideration is that the MRI was performed at a time point where any information provided by the study was too late to act upon in a way that would alter patient outcomes. For this same reason, CTA, which can often be obtained more quickly, may have improved patient outcomes due to more rapid availability of information. Finally, delaying discharge to obtain an MRI may prolong hospitalization, leading to delayed initiation of rehabilitation and increasing the likelihood that patients may develop a hospital acquired infection or other complication that may affect overall outcome.

There are multiple limitations to this study. First, it was a retrospective review of prospectively collected data. Follow-up of patients was limited by what was recorded in the electronic medical record. Patients who sought care at other hospitals or died without notification of the hospital would not have been captured in the electronic medical record. Second, the decision to use CT or MRI was not random. There were baseline differences between groups which may have reflected the decision to do further testing. For example, patients who had CT alone had higher NIHSS scores at admission. This finding may have reflected the fact that clinicians either had no difficulty seeing the infarction on initial CT or preferred not to pursue additional testing with MRI because of the patient’s condition. Third, the study was conducted at a single center and was reflective of the practice style of the clinicians who worked there.

In conclusion, this retrospective analysis of a prospectively collected database at a single institution showed that the use of an MRI during hospitalization was not associated with a reduced risk of death, recurrent stroke, or myocardial infarction within one year of follow-up. The results suggest that treatment strategies may not necessarily have been influenced by imaging modality or that changes in treatment strategy based on MRI did not improve outcome. A randomized trial of different imaging modalities should be considered.

CONFLICT OF INTEREST

The authors confirm that this article content has no conflicts of interest.

ACKNOWLEDGEMENT

None Declared.

REFERENCES

[1] Schellinger PD, Bryan RN, Caplan LR, et al. Evidence-based guideline: The role of diffusion and perfusion mri for the diagnosis of acute ischemic stroke: Report of the therapeutics and technology assessment subcommittee of the american academy of neurology Neurology 2010; 75: 177-85.
[2] Adams HP Jr, del Zoppo G, Alberts MJ, et al. Guidelines for the early management of adults with ischemic stroke: A guideline from the american heart association/american stroke association stroke council, clinical cardiology council, cardiovascular radiology and intervention council, and the atherosclerotic peripheral vascular disease and quality of care outcomes in research interdisciplinary working groups: The american academy of neurology affirms the value of this guideline as an educational tool for neurologists Stroke 2007; 38: 1655-711.
[3] Easton JD, Saver JL, Albers GW, 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; 40: 2276-93.
[4] Luengo-Fernandez R, Gray AM, Rothwell PM. Study obotOV. A population-based study of hospital care costs during 5 years after transient ischemic attack and stroke Stroke 2012; 43: 3343-51.
[5] Fiebach JB, Schellinger PD, Gass A, et al. Stroke magnetic resonance imaging is accurate in hyperacute intracerebral hemorrhage: A multicenter study on the validity of stroke imaging Stroke 2004; 35: 502-6.
[6] Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: A prospective comparison Lancet 2007; 369: 293-8.
[7] Kidwell CS, Chalela JA, Saver JL, et al. Comparison of mri and ct for detection of acute intracerebral hemorrhage JAMA 2004; 292: 1823-30.
[8] Barber PA, Hill MD, Eliasziw M, et al. Imaging of the brain in acute ischaemic stroke: Comparison of computed tomography and magnetic resonance diffusion-weighted imaging J Neurol Neurosurg Psychiatry 2005; 76: 1528-33.
[9] Ringleb PA, Schwark C, Kohrmann M, et al. Thrombolytic therapy for acute ischaemic stroke in octogenarians: Selection by magnetic resonance imaging improves safety but does not improve outcome J Neurol Neurosurg Psychiatry 2007; 78: 690-3.
[10] Alberts MJ, Hademenos G, Latchaw RE, et al. Recommendations for the establishment of primary stroke centers. Brain attack coalition JAMA 2000; 283: 3102-9.
[11] Ambrose J. Computerized transverse axial scanning of the brain Proc R Soc Med 1973; 66: 833-4.
[12] Tissue plasminogen activator for acute ischemic stroke. The national institute of neurological disorders and stroke rt-pa stroke study group N Engl J Med 1995; 333: 1581-7.
[13] Hacke W, Kaste M, Bluhmki E, et al. Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke N Engl J Med 2008; 359: 1317-29.
[14] Roger VL, Go AS, Lloyd-Jones DM, et al. J Heart disease and stroke statistics--2011 update: A report from the american heart association Circulation 2011; 123: e18-e209.
[15] Doyle FH, Gore JC, Pennock JM, et al. Imaging of the brain by nuclear magnetic resonance Lancet 1981; 2: 53-7.
[16] Moseley ME, Kucharczyk J, Mintorovitch , et al. Diffusion-weighted mr imaging of acute stroke: Correlation with t2-weighted and magnetic susceptibility-enhanced mr imaging in cats AJNR Am J Neuroradiol 1990; 11: 423-9.
[17] Ay H, Gungor L, Arsava EM, et al. A score to predict early risk of recurrence after ischemic stroke Neurology 2010; 74: 128-35.
[18] Giles MF, Albers GW, Amarenco P, et al. Addition of brain infarction to the abcd2 score (abcd2i): A collaborative analysis of unpublished data on 4574 patients Stroke 2010; 41: 1907-3.
[19] Weimar C, Diener HC, Alberts MJ, et al. The essen stroke risk score predicts recurrent cardiovascular events: A validation within the reduction of atherothrombosis for continued health (reach) registry Stroke 2009; 40: 350-4.
[20] Kernan WN, Viscoli CM, Brass LM, et al. The stroke prognosis instrument ii (spi-ii) : A clinical prediction instrument for patients with transient ischemia and nondisabling ischemic stroke Stroke 2000; 31: 456-62.
[21] Olesen JB, Lip GY, Hansen ML, et al. Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: Nationwide cohort study BMJ 2011; 342: d124.
[22] Coutts SB, O'Reilly C, Hill MD, et al. Computed tomography and computed tomography angiography findings predict functional impairment in patients with minor stroke and transient ischaemic attack Int J Stroke 2009; 4: 448-53.
[23] Facts about primary stroke center certification http://www.heart.org/idc/groups/heart-public/@wcm/@gsa/documents/downloadable/ucm_432686.pdf [Accessed: 27th Nov, 2012];