Report of fogging effect on fast FLAIR magnetic resonance images of cerebral infarctions.

We report a case of multiple small, presumably iatrogenic, cortical infarctions detected incidentally on magnetic resonance imaging (MRI) 5 days after preoperative cerebral angiography but not apparent 12 days after the angiography on noncontrast MRI including a fast fluid-attenuated inversion recovery (FLAIR) sequence. However, the lesions showed marked contrast enhancement with gadolinium on postcontrast T1-weighted images. Cortical laminar necrosis was observed on MRI 35 days after the initial angiographic study. This case shows that the MRI fogging effect may prevent detection of small cortical infarctions in the subacute stage even on fast FLAIR sequences. Postcontrast images should be studied to reduce diagnostic errors associated with this effect.