Yield of combined perfusion and diffusion MR imaging in hemispheric TIA

Abstract

Objective: Transient ischemic attacks (TIA) predict future stroke. However, there are no sensitive and specific diagnostic criteria for TIA and interobserver agreement regarding the diagnosis is poor. Diffusion-weighted MRI (DWI) demonstrates acute ischemic lesions in approximately 30% of TIA patients; the yield of perfusion-weighted MRI (PWI) is unclear. Methods:We prospectively performed both DWI and PWI within 48 hours of symptom onset in consecutive patients admitted with suspected hemispheric TIAs of Ͻ24 hours symptom duration. Two independent raters, blinded to clinical features, assessed the presence and location of acute DWI and PWI lesions. Lesions were correlated with suspected clinical localization and baseline characteristics. Clinical features predictive of a PWI lesion were assessed. Results:Forty-three patients met the inclusion criteria. Thirty-three percent had a PWI lesion and 35% had a DWI lesion. Seven patients (16%) had both PWI and DWI lesions and 7 (16%) had only PWI lesions. The combined yield for identification of either a PWI or a DWI was 51%. DWI lesions occurred in the clinically suspected hemisphere in 93% of patients; PWI lesions in 86%. PWI lesions occurred more frequently when the MRI was performed within 12 hours of symptom resolution, in patients with symptoms of speech impairment, and among individuals younger than 60 years. Transient ischemic attacks (TIA) are defined as sudden, temporary attacks (Ͻ24 hours) with focal symptoms attributable to dysfunction of one artery of the brain. The risk of stroke after a TIA is up to 10% in the first week following symptom onset. Conclusions:1 Recent studies demonstrated that a prompt etiologic investigation followed by the initiation of an appropriate prevention strategy can substantially reduce this risk.2,3 Hence, confirmation of the diagnosis of TIA is a major challenge since in most cases the clinical deficit has resolved at the time of evaluation and conventional brain imaging does not detect most conditions that masquerade as a TIA. 4 In multimodal MRI, diffusion-weighted imaging (DWI) demonstrates the presence of severe cytotoxic ischemic injury within minutes, which provides an estimate of the ischemic core, 5,6 and perfusion-weighted imaging (PWI) provides an assessment of cerebral hemodynamics.

An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation

“…With respect to the timing of patient assessment after the index event, in 10 studies TIA patients were assessed within 24 hours of symptoms onset, 62,69,87,[134][135][136]138,143,155,161 in six studies within 48 hours, 137,139,141,142,150,165 in one study 140 within 72 hours and in one study 160 within 7 days. Another four studies 9,61,132,144 reported that 'patients were assessed as soon as possible after the event' but did not give a time.…”

“…One study 128 included a highly selected sample of patients with TIA and carotid stenosis, and three studies 65,141,155 excluded patients with specific conditions [i.e. cardioembolic events or blood coagulation disorders, AF and posterior circulation TIAs, respectively].…”

“…152,167,177,186,209 For the purpose of the present HTA project, we systematically reviewed studies that assessed ABCD score of ≥ 4 or < 4 in TIA patients (see Chapter 4). Among 26 cohorts, 15 cohorts reported the risk of recurrent stroke at 7 days; 18 cohorts at 90 days, and three cohorts at > 90 days, and nine studies 63,139,141,[151][152][153][154]160,165 provided stroke risk data at both 7 and 90 days. Among these nine studies 63,139,141,[151][152][153][154]160,165 the pooled estimates for stroke risk at 7 days were 4.76% (95% CI 2.40% to 8.70%) in patients with an ABCD2 score of ≥ 4 and 1.6% (95% CI 1.0% to 3.4%) in patients with score of < 4; at 90 days the risk was 8.2% (95% CI 4.7% to 14.0%) and 2.7% (95% CI 1.5% to 4.7%), respectively.…”

Early stroke risk and ABCD2 score performance in tissue- vs time-defined TIA

“…In 3 cohorts, follow-up data were either incomplete or unavailable beyond 7 days. 19,27,28 18 in CT cohorts). Of those imaged with DWI and CT, 72 (2.2%; 95% CI 1.8 -2.8) and 73 (5.3%; 95% CI 4.2-6.7), respectively, had a recurrent stroke at 7 days.…”

The role of imaging in acute ischemic stroke

“…151 DWI can also assess the degree of brainstem infarction before proceeding with endovascular treatment.…”