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Introduction: We analyze our preliminary experience using the PoleStar N20 mobile intraoperative MR (iMR) system as an adjunct for pediatric brain tumor resection., Methods: We analyzed 11 resections in nine children between 1 month and 17 years old. After resection, we acquired iMR scans to detect residual tumor and update neuronavigation. We compared final iMR interpretation by the neurosurgeon with early postoperative MR interpretation by a neuroradiologist., Results: Patient positioning was straightforward, and image quality (T1 7-min 4-mm sequences) sufficient in all cases. In five cases, contrast enhancement suspect for residual tumor was noted on initial postresection iMR images. In one case, a slight discrepancy with postoperative imaging after 3 months was no longer visible after 1 year. No serious perioperative adverse events related to the PoleStar N20 were encountered, except for transient shoulder pain in two., Conclusions: Using the PoleStar N20 iMR system is technically feasible and safe for both supra- and infratentorial tumor resections in children of all ages. Their small head and shoulders favor positioning in the magnet bore and allow the field of view to cover more than the area of primary interest, e.g., the ventricles in an infratentorial case. Standard surgical equipment may be used without significant limitations. In this series, the use of iMR leads to an increased extent of tumor resection in 45 % of cases. Correlation between iMR and early postoperative MR is excellent, provided image quality is optimal and interpretation is carefully done by someone sufficiently familiar with the system.

Objective: Tight filum syndrome (TFS) is caused by a thick (abnormal T1 MRI), shortened (low-lying conus), or non-elastic filum (strictly normal MRI). We carefully analyzed children treated for suspect TFS with or without radiological abnormalities., Methods: Twenty-five children, operated between 2002 and 2009, were retrospectively identified. All children had been evaluated by a multidisciplinary team preoperatively. Symptoms, signs and diagnostic test results were categorized (neurologic, urologic, orthopedic, dermatologic) and compared pre- and one year postoperatively. Normal MR was defined as conus medullaris (CM) at or above mid-body L2 and filum diameter less than 2 mm. Occult TFS (OTFS) was defined as TFS with normal MR., Demographics: 17 girls, 8 boys, age 2-18 years, including 11 syndromal children., Clinical Presentation: all children had problems in the neurologic category and at least one other category: urologic (n = 17), orthopedic (n = 21), and dermatologic (n = 11). MR findings: low-lying CM (n = 14) including 2 with thick filum, normal CM but fatty filum (n = 2), strictly normal (n = 9). Clinical outcome one year postoperatively: neurologic 20 improved, 5 stabilized; urologic 13 improved, 3 stabilized, 1 worsened; orthopedic (8 children presenting with scoliosis) 3 improved, 4 stabilized, 1 worsened. All children with OTFS (n = 9) improved in at least one and 8 improved in all affected categories., Conclusions: Children with strong clinical suspicion for TFS (≥ 2 affected categories) with or without abnormal MR findings will likely benefit from surgery. In such cases we suggest a detailed full spine MR, a multidisciplinary diagnostic work-up, and eventual untethering through an interlaminar microsurgical approach., (Copyright © 2011 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)