The California, ABCD, and Unified ABCD2 Risk Scores and the Presence of Acute Ischemic Lesions on Diffusion-Weighted Imaging in TIA Patients
Background and Purpose— Some clinical models, like California ABCD and unified ABCD2 scores, are now available to predict the early risk of stroke after a TIA. Despite the transitivity of symptoms, DWI identified an area of acute brain ischemia in almost half of patients. It would be interesting to know how the presence of DWI abnormalities relates to clinical risk scores to plan other prognostic variables or to recommend the performance of DWI.
Methods— We prospectively studied 135 consecutive TIA patients visited by the neurologists in our institution. All patients underwent DWI (3.8±1.7 days after symptoms onset). Clinical risk scores (California, ABCD, and ABCD2) were calculated prospectively for each patient. The identification of acute ischemic lesions (positive DWI) was related to the presence of clinical features and clinical risk scores.
Results— DWI were positive in 67 (49.6%) patients. After Bonferroni adjustment, elevated ABCD, ABCD2, and California scores were not associated with a positive DWI. However, some clinical symptoms such as facial palsy and motor weakness were associated with a positive DWI (P<0.001). The logistic regression model identified only facial palsy as an independent predictor of acute ischemic lesions (odds ratio 6.26, 95% CI 2.49 to 15.71, P<0.001).
Conclusion— Clinical symptoms such as motor impairment, but not clinical risk scores, were associated with a positive DWI. Performing a DWI may add prognostic information to clinical risk scales as a predictor of stroke recurrence after TIA in future large studies.
Since 2002, when the TIA Working Group proposed a new definition of transient ischemic attack (TIA) based on a lower duration of symptoms (less than 1 hour) and on the demonstration of absence of ischemic lesions on neuroimaging, diffusion-weighted images (DWI) became essential for the management of these patients.1 Despite the transitivity of symptoms, DWI reveals an area of water restriction attributable to acute brain ischemia in almost half of patients (range 16% to 67%).2–4
Recently 3 prognostic scores for the short-term risk of stroke after TIA have been proposed: the California, ABCD, and unified ABCD2 risk scores.5–7 All these scores rely on a summation of clinical factors. Moreover, recent studies have demonstrated the high early risk of stroke in classical TIA patients with acute ischemic lesions on DWI.4
Our aim was to determine the association between the California, ABCD, and unified ABCD2 clinical risk scores and the presence of acute ischemic lesions on DWI in TIA patients.
Subjects and Methods
We prospectively studied 161 consecutive patients with transient neurological deficits attended by a neurologist in the emergency room, from January 2006 to January 2008. The study was approved by the institutional ethics committee, and all patients provided written informed consent. TIA was defined as a reversible episode of neurological deficit of ischemic origin that resolved completely within 24 hours.8 A total of 11 clinical episodes were attributable to causes other than brain ischemia: hyponatremia (1 case), psychosomatic disorders (2 cases), migraine (3 cases), epilepsy (3 cases), cerebral tumor (2 cases), cerebral amyloid angiopathy (1 case), subdural hematoma (1 case), and transient global amnesia (1 case). Two patients refused to give informed consent. We excluded patients with contraindications to MRI, age <18 years, or serious comorbid illness. Finally, 135 patients were included. An MRI was acquired using a 1.5-T whole-body imager system with 24-mT/m gradient strength, 300-ms rise time, and an echo-planar–capable receiver equipped with a gradient overdrive (Philips Intera 1.5 T, MRI scanner). The images obtained included axial T2-weighted turbo spin-echo (4800/120/3; TR/TE/excitations), T1-weighted spin-echo (540/15/2), turbo fluid-attenuated inversion recovery (8000/2200/120/2; TR/TI/TE), and echo-planar diffusion images (3900/95). The DWI were obtained with a single-shot spin-echo echo-planar pulse sequence with diffusion gradient b values of 1000, s/mm2 along all 3 orthogonal axes over 20 axial sections, using 6-mm-thick sections, an interslice gap of 1 mm, a field of view of 230 mm, and 256×256 matrix. Tissue abnormality (positive DWI) was defined as areas of high signal intensity on isotropic DWI reflecting an acute ischemic lesion. In every case, the MRI was performed before a new follow-up stroke (6 patients with very early stroke recurrence were excluded). All patients underwent clinical evaluation by a stroke neurologist. California, ABCD, and unified ABCD2 risk scores were calculated prospectively for each patient. TIAs were classified etiologically according to the Trial of ORG 10172 (TOAST).9
Data are reported using standard descriptive statistics. Univariate analysis was performed to detect variables associated with a positive DWI. Finally, a multivariate logistic regression was conducted for variables that reached P<0.1 on the univariate analysis. A probability value <0.05 was considered significant. A Bonferroni correction for multiple comparisons was applied to all significant associations to reduce the risk of finding false-positive associations.
A total of 135 patients were included in the study. The mean age of all patients was 68.7±11.5 years, and 81 (60.0%) were male (Table). Hypertension, present in 90 (66.7%) cases, was the main vascular risk factor. Regarding clinical risk scores, the mean California score was 3.09±1.05, mean ABCD score was 4.16±1.15, and mean ABCD2 score was 4.41±1.28. Acute ischemic lesions on DWI were identified in 67 (49.6%, 95 CI 41.16 to 58.03) TIA patients. The univariate analysis revealed (Table) that clinical symptoms such as facial palsy (P<0.001) and motor weakness of the face or arm, or leg (P<0.001) were associated with a positive DWI. However, associations with the following symptoms did not reach statistical significance after Bonferroni adjustment: dysarthria (P=0.010), limb weakness (P=0.047), absence of aphasia (P=0.022), absence of isolated sensory symptoms (P=0.030), and undetermined territory symptoms (P=0.005). No association was observed between the duration of clinical symptoms and the California, ABCD, and unified ABCD2 scores.
In the logistic regression model, only facial palsy remained as an independent predictor of a positive DWI (odds ratio 6.26, 95% CI 2.49 to 15.71, P<0.001).
In our study we did not find any association between clinical risk scores (California, ABCD risk, and unified ABCD2 scores) and a positive DWI. The main explanation for this is that only motor impairment, and especially facial palsy, predicted the abnormality of DWI. Interestingly, other components of these clinical risk scores, like duration of symptoms, age, hypertension, or DM, were not associated with positive DWI.
DWI is highly sensitive to acute ischemic lesions. Nevertheless, the diagnosis of TIA is a difficult clinical problem because many of the symptoms may have resolved before patients arrive at the hospital, and there are many different conditions such as seizure, migraine, cerebral tumor, subdural hematoma, or syncope that mimic cerebral ischemic events. The association of motor impairment and facial palsy with DWI in acute ischemic lesions could be explained by a greater likelihood of a correct diagnosis of transient brain ischemia events.10 Furthermore, isolated facial palsy and the combination of facial palsy and limb impairment had stronger associations with speech impairment than the association between speech impairment and motor limb impairment: 90%, 80%, and 40.5%, respectively. Therefore, we believe that facial palsy may be related to carotid artery territory ischemia. Several case series have shown that false-negative DWI usually occur in brain stem strokes.11
Our study has several limitations. Namely, if the MRI was performed earlier we would be able to include patients with early stroke recurrence. Nevertheless, among the 6 TIA patients excluded for this reason, their ABCD scores were ≤5 in all cases and ABCD2≤5 in 4 cases. Moreover, the use of a high-resolution DWI sequence would increase the prevalence of acute lesions.12 However, the percentage of positive DWI was higher than previous studies. The small sample size prevents us from generalizing the results. Prospective multicenter studies would be necessary to clarify the prognostic usefulness of performing DWI scans in TIA patients.
Recently Redgrave et al studied this topic, reaching slightly different conclusions.13 In their study, patients were scanned later (median interval of 15 days), and they did not find an association between motor weakness and positive DWI whereas they found an association with dysarthria.
In conclusion we found that some clinical symptoms, such as motor impairment and especially facial palsy, were associated with acute ischemic lesions in TIA patients, but not with previously established clinical risk scores. Therefore, future large prospective studies would be required to determine the independent predictive value of DWI in TIA patients.
Sources of Funding
This study was funded in part by the Ministerio de Sanidad y Consumo, Instituto de Salud Carlos III: FIS Number PIO81398.
- Received September 22, 2008.
- Revision received November 9, 2008.
- Accepted November 13, 2008.
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