Diffusion-weighted magnetic resonance imaging identifies the "clinically relevant" small-penetrator infarcts

Background: Most patients initially seen with a clinical syndrome consisten t with a small-penetrator infarct (SPI) also harbor multiple, chronic, hype rintense, white matter lesions on conventional magentic resonance imaging t ie, T2-weighted image [T2WI] and fluid-attenuation inversion recovery [FLAI R] imaging). Diffusion-weighted imaging (DWI) can identify the clinically r elevant "index infarction" in such circumstances, since it differentiates b etween acute and chronic lesions. Objective: To determine the clinical and radiological predictors associated with misidentification of an SPI as acute using T2WI and FLAIR images in p atients with an acute SPI seen on DWI. Patients: Sixty-seven consecutive patients who had an SPI. Methods: Two independent examiners, provided with brief clinical informatio n, but blinded to DWI findings, sought a clinically appropriate lesion on T 2WI and FLAIR imaging in 67 consecutive patients found to have an SPI seen on DWI. Results: The index infarction based on evaluation of T2WI or FLAIR images w as in a different location than the acute lesion as identified by DWI in 9 (13%) and 11 (16%) of 67 patients, respectively. Both T2WI and FLAIR imagin g were rated normal in another 9% of the patients. Multivariate analysis sh owed that small lesion size (<10 mm) was the only predictor of misidentifyi ng the clinically appropriate lesion on conventional magnetic resonance ima ging (P<.01). Conclusions: T2-weighted imaging and FLAIR imaging fail to identify the cli nically relevant SPI in almost one quarter of the patients found to have a lesion on DWI. The characteristics of DWI make it well suited for the detec tion of acute small infarcts. Diffusion-weighted imaging is necessary to co nsistently define the clinical-anatomical relations in patients initially s een with SPIs.