Transient ischemic attack and stroke can be differentiated by analyzing early diffusion-weighted imaging signal intensity changes

Background - Diffusion-weighted imaging (DWI) has been established to diagnose acute cerebral ischemia. Signal intensity changes occur not only in patients with definite stroke but also in up to 67% of transient ischemic attack (TIA) patients. We investigated the predictive value of DWI signal intensity changes to distinguish between TIA and stroke. Methods - Clinical data, conventional magnetic resonance imaging (MRI), and DWI were collected in 60 consecutive patients with TIA and 37 consecutive patients with stroke. DWI was performed within 24 hours after symptom onset. Using an image analyzing system, we calculated the ratio of the lesion and corresponding contralateral normal tissue average signal intensity (rAI). Results - Eighteen of 60 TIA patients (30%) revealed focal abnormalities on DWI. The mean duration of symptoms was 5.3 hours in TIA patients with DWI lesions and 5.2 hours in patients without lesions. The time to DWI was comparable in TIA and stroke patients. Even within 6 hours after symptom onset, the signal intensity was significantly higher (P = 0.03) in stroke patients (n = 13, rAI = 1.26) as compared with TIA patients with DWI lesions (n = 9, rAI = 1.16). Conclusions - Our data indicate that already within 6 hours after symptom onset, TIA and stroke might be differentiated by analyzing the signal intensity of the lesions.