title: Orbit-associated tumors: navigation and control of resection using intraoperative computed tomography.
abstract: OBJECT Treatment of skull base lesions is complex and usually requires a multidisciplinary approach. In meningioma, which is the most common tumor entity in this region, resection is considered to be the most important therapeutic step to avoid tumor recurrence. However, resection of skull base lesions with orbital or optic nerve involvement poses a challenge due to their anatomical structure and their proximity to eloquent areas. Therefore the main goal of surgery should be to achieve the maximum extent of resection while preserving neurological function. In the postoperative course, medical and radiotherapeutic strategies may then be successfully used to treat possible tumor residues. Methods to safely improve the extent of resection in skull base lesions therefore are desirable. The current study reports the authors' experience with the use of intraoperative CT (iCT) combined with neuronavigation with regard to feasibility and possible benefits of the method. METHODS Those patients with tumorous lesions in relationship to the orbit, sphenoid wing, or cavernous sinus who were surgically treated between October 2008 and December 2013 using iCT-based neuronavigation and in whom an intraoperative scan was obtained for control of resection were included. In all cases a second iCT scan was performed under sterile conditions after completion of navigation-guided microsurgical tumor resection. The surgical strategy was adapted accordingly; if necessary, resection was continued. RESULTS Twenty-three patients (19 with WHO Grade I meningioma and 4 with other lesions) were included. The most common clinical symptoms were loss of visual acuity and exophthalmus. Intraoperative control of resection by iCT was successfully obtained in all cases. Intraoperative imaging changed the surgical approach in more than half (52.2%) of these patients, either because iCT demonstrated unexpected residual tumor masses or because the second scan revealed additional tumor tissue that was not detected in the first scan due to overlay by osseous tumor parts; in these cases resection was continued. In the remaining cases resection was concluded as planned because iCT verified the surgeon's microscopic estimation of tumor resection status. Postoperative visual outcome was favorable in more than 80% of patients. CONCLUSIONS Intraoperative CT allows control of resection in case of uncertainty and can help to improve the extent of maximal safe resection, especially in case of osseous tumor parts and masses within the orbit.
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Terpolilli
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Walter
authors.initials: W
authors.lastname: Rachinger
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Mathias
authors.initials: M
authors.lastname: Kunz
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Niklas
authors.initials: N
authors.lastname: Thon
authors.affiliation: Clinical Radiology, Munich University Medical Center, Munich, Germany.
authors.forename: Wilhelm H
authors.initials: WH
authors.lastname: Flatz
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Jörg-Christian
authors.initials: JC
authors.lastname: Tonn
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Christian
authors.initials: C
authors.lastname: Schichor
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology* / Q000601:surgery*; D008579:Meningioma / Q000473:pathology* / Q000601:surgery*; D008866:Microsurgery / Q000379:methods*; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000473:pathology* / Q000601:surgery*; D038361:Neuronavigation / Q000379:methods*; D009918:Orbital Neoplasms / Q000473:pathology* / Q000601:surgery*; D012086:Reoperation; D012680:Sensitivity and Specificity; D019292:Skull Base Neoplasms / Q000473:pathology* / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CN = cranial nerve; NNS = neuronavigational system; iCT = intraoperative CT; iMRI = intraoperative MRI; image-guided surgery; intraoperative computed tomography; neuronavigation; oncology; skull base; spheno-orbital meningioma