Frank hypointensity (i.e. dark hue) on CT of the brain, particularly if involving greater than one-third of the middle cerebral artery (MCA) territory, is a contraindication to treating acute ischemic stroke with tPA.
Early signs of infarct on brain CT, regardless of extent, are NOT contraindications to treatment.
References
Latchaw et al. Recommendations for imaging acute ischemic stroke: A scientific statement from the American Heart Association. Stroke 2009;40:3646-78.
