Negative diffusion-weighted imaging after intravenous tissue-type plasminogen activator is rare and unlikely to indicate averted infarction

Abstract

Background and purpose: Some patients treated with intravenous (IV) tissue-type plasminogen activator (tPA) have negative diffusion-weighted imaging (DWI) on follow-up imaging. Without a visible infarct, there may be uncertainty as to whether the patient was having a stroke that was averted by tPA or whether the symptoms had not been cerebrovascular in origin. We evaluated patients presenting with suspected acute stroke with a positive DWI lesion before IV tPA to determine the probability of finding a negative DWI up to 48 hours after treatment.

Methods: We included patients from the Lesion Evolution in Stroke and Ischemia On Neuroimaging (LESION) project who had acute MRI screening with a positive DWI lesion before IV tPA treatment and had follow-up MRI up to 48 hours later. Experienced readers interpreted all acute and follow-up MRIs looking for ischemic lesions on DWI.

Results: There were 231 patients who met study inclusion criteria, of which 225 patients (97.4%) had a persistent positive DWI corresponding to the acute stroke lesion on all follow-up imaging. Four patients (1.7%) had transient DWI lesion reversal with positive DWI on subsequent follow-up imaging. There were only 2 cases (0.9%) of complete DWI lesion reversal on all follow-up imaging.

Conclusions: Averted infarction after IV tPA is rare, occurring in 0.9% of patients with pretreatment positive DWI evidence of acute ischemia. For IV tPA-treated patients who have a negative DWI on follow-up imaging, a cause other than acute stroke should be explored.

Keywords: MRI; acute stroke; diffusion-weighted imaging; tPA; thrombolytic therapy.

Figure 1. Example of transient DWI lesion reversal

Eighty-one year old woman with acute onset left hemiparesis and dysathria, NIHSS=1, with a transient DWI lesion reversal pattern: positive DWI lesion (A) on pre-treatment MRI, negative DWI (B) and ADC (not shown) at 2 hours post-treatment with IV tPA but positive DWI at 24 hours (C) and positive FLAIR (D) at 5 days.

Figure 2. Averted infarction in the medulla

Forty year old man with acute onset left hemisensory deficit, NIHSS=3, with an averted infarction pattern: had a small positive DWI lesion in the right medulla (A) with subtle ADC hypodensity (B) on pre-treatment MRI but negative DWI at 2 (C) and 24 hours (D) post-treatment with IV tPA. No other evidence of acute cerebral ischemia was seen on MRI.

Figure 3. Averted infarction in the frontal lobe

Forty-nine year old woman with acute onset right hemiparesis, dysarthria, and aphasia, NIHSS=6, with an averted infarction pattern: had a small positive DWI lesion in the left MCA (A) with ADC hypodensity (B) on pre-treatment MRI but negative DWI at 2 (C) and 24 hours (D) post-treatment with IV tPA. DWI at 2 (C) and 24 hours (D) post-treatment with IV tPA as well as FLAIR (not shown) at those time points did demonstrate satellite acute ischemic lesions in the right frontal (black arrows) and occipital lobes (not shown).