Nonionic iodinated contrast-induced encephalopathy is a rare complication in neuroendovascular therapy and is supposed to be caused by the osmotic disruption of the blood-brain barrier resulting from repeated contrast injections into a single vessel. But its exact etiological mechanisms remain uncertain. We report a unique case of contrast-induced encephalopathy after coil embolization of unruptured aneurysm. An abnormal high signal intensity lesion on arterial spin-labeled perfusion weighted imaging-magnetic resonance imaging (PWI-MRI) persisted until more than one year after the procedure without any neurological sequelae or any obvious organic abnormalities recognized on MRI.
A 66-year-old woman with an incidentally found unruptured left paraclinoid aneurysm was treated with endovascular balloon-assisted coil embolization. The procedure was successfully accomplished using about 80 ml of contrast medium (iomeprol) injected into the left internal carotid artery. However, she manifested prolonged consciousness disturbance, aphasia, and right hemi-paresis directly after the procedure and seizure on the next day. Immediate computed tomography revealed the cortical enhancement in the left cerebral hemisphere. Diffusion weighted imaging-MRI six hours and two days after the procedure revealed no particular abnormality. Her clinical symptoms completely resolved four days after the procedure with administration of steroid, glycerin and edaravone. She was discharged with no neurological deficit, but the abnormal high signal intensity lesion in the left temporo-parietal lobe was demonstrated on the serial PWI-MRI from two days to 12 months after the procedure.
We speculate that some further mechanisms such as ischemia, immunological response or a genetic factor may be involved in this case, thus increasing her susceptibility to neurotoxic effects of the contrast medium.