Large Residual Pilocytic Astrocytoma After Failed Ultrasound-Guided Resection: Intraoperative Ultrasound Limitations Require Special Attention.

While benefits of neurosurgical intraoperative ultrasound (IOUS) are reported frequently, this method still has some significant pitfalls, which are described less often. However, sufficient knowledge on dealing with IOUS drawbacks, particularly various image artifacts, is important for successful surgery. We report a case of failed IOUS-guided pediatric cerebellar pilocytic astrocytoma resection, incorrectly evaluated as gross total resection according to IOUS. A large tumor residuum was left in place. Successful IOUS-guided reoperation using new IOUS technology and appropriate ultrasound imaging technique are described. The most probable reasons for initial resection failure and crucial points of reoperation, predominantly dealing with IOUS artifacts, are discussed. Neurosurgeons should be aware of IOUS limitations and have sufficient knowledge about how to overcome them before adopting routine use of this intraoperative imaging modality.