CT and MRI findings after stereotactic resection of brain lesions.

OBJECTIVE

To describe postoperative CT and MRI findings and their time course in uncomplicated cases after stereotactic volumetric resections of brain lesions.

MATERIALS AND

METHODS

One-hundred twenty-eight imaging studies (CT, 86; MRI, 42), performed 6 h to 2 years after 52 stereotactic operations, were retrospectively reviewed and analyzed in relation to time of surgery in cases without complications.

RESULTS

The extent of resection bed did not change during the first week after operation; reduction of size then began and continued up to 3-6 months. Mass effect and edema showed no changed during the first 4 days, then later regressed gradually. Pneumocephalus was found in 58% of cases in the first 3 weeks, but never later. Benign, surgically-induced enhancement appeared at the margins of encephalotomy and retractor at the end of the first postoperative week, became more prominent during the following weeks, and lasted up to 3-5 months. In the majority of cases enhancement prevented recognition of the residual tumor. Dural enhancement was observed at the craniotomy site very early after the operation and persisted up to 1 year. Meningeal enhancement over convexities was found in 44% of MRI studies.

CONCLUSION

Extent of the resection bed, mass effect, edema, and pneumocephalus show, in uncomplicated cases, a regular regression during the postoperative period. The time course of enhancement is complex and can be a source of diagnostic misinterpretation.