Gas bubbles in polymethylmethacrylate cranioplasty simulating abscesses: CT appearance.

Polymethylmethacrylate (PMMA) cranioplasty procedures were performed on 20 patients over a 2-year period. Nine of these patients had a total of 17 CT examinations, performed when clinically indicated. On 16 of the 17 CT scans, the appearance of the cranioplasty plate was characteristic of plates with gas bubbles. The appearance of these bubbles was stable over an extended period of time, ruling out clinical reasons for this appearance. The original interpretations of the CT scans were variable, inconclusive, or even erroneous. An understanding of the application of PMMA plates and their characteristics is necessary to accurately interpret the CT appearance of the PMMA cranioplasty plate.