Article
Electromagnetic-guided surgery in the semi-sitting position for small midline processes of the posterior fossa
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Published: | May 13, 2014 |
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Objective: Electromagnetic (EM) guided neuronavigation is an innovative technique and an excellent endorsement to the optical navigation systems. Here we performed a feasibility study using EM guided neuronavigation for surgery in the semi-sitting position.
Method: Ten patients (three children and seven adults; age between 13 years and 84 years, mean age 40.9 years) with different small neoplasms in the posterior fossa involving midline structures underwent 3D-MRI-based EM guided neuronavigated surgery. Intraoperative registration by surface matching was performed in supine position. Thereafter, the head was sharp fixed in the Mayfield clamp and the patient was transferred for surgery in the semi-sitting position. Confirmation of accuracy was achieved by checking for deviations of the position of tragus, bregma, nasion (x=lateral, y=anteroposterior, z=vertical). For intraoperative accuracy control screenshots were correlated to the microscopic view of the identified pathological structure documented by intraoperative pictures.
Results: Referencing of the patient in supine position followed by sharp head fixation and positioning in the semi-sitting position without losing of navigation accuracy was possible in all ten cases. Accuracy of registration was within 2mm in any case in all three axes as determined by checking the positions for tragus, nasion and bregma. Intraoperative accuracy for small midline processes was good enough (deviation between 2-5 mm from the target point) and EM navigation was considered helpful by the surgeon in all ten cases. Histopathological results were pilocytic astrocytoma (2), recurrent medulloblastoma (1), pineocytoma (1), metastasis (3), diffuse large B-cell lymphoma (1), hemorrhagic brainstem cavernoma (1) and mixed germ-cell tumor (1).
Conclusions: EM guided neuronavigation in the semi-sitting position was technically feasible and enabled fast and accurate referencing of the patient for navigation without loss of accuracy despite sharp head fixation and repositioning of the patient. In contrast to conventional optical neuronavigation there were no line-of-sight problems.