Utility of frameless stereotaxy in the resection of skull base and Basal cerebral lesions in children.

Since 1991, we have performed nearly 300 stereotactic procedures using the ISG viewing wand on a variety of cranial lesions in patients under 22 years of age. Of these, 38 procedures were performed on 34 patients for basal cerebral and skull base lesions. Our patients ranged in age from 3.5 months to 22 years with a mean age of 9.45 years. There were 18 females and 16 males. Twenty-one patients had basal cerebral lesions located in the thalamus (10), basal ganglia (2), third ventricle (2), and hypothalamus (7). Thirteen patients had skull base lesions located within the anterior optic apparatus (3), sella turcica (4), middle and posterior cranial fossae (4), and craniocervical region (2). Preoperative CT and/or MRI scan images were taken as a volume acquisition and transferred to the computer workstation utilizing the ISG Wand software. This workstation was transferred to the operating room where it was calibrated to a faro Surgicom arm which interfaces with the patient and the three-dimensional radiological image. The ISG Wand was utilized to plan the scalp and bone flaps and to select the optional trajectory to lesion. The surgical approaches which were specifically used in this series with the ISG Wand included transcallosal (15), pterional (5), frontal (3), subtemporal (4), transsphenoidal (3), temporal (3), tumor cyst shunt insertion (1), burr hole drainage (1), transoral (2), bifrontal (1), bifrontal mid facial (1), and transnasal (1). Although brain shift occurred following craniotomy and with brain retraction, the relative immobility of these lesions at the skull or cerebral base permitted an accurate targeting of all lesions with an error range of 1.0-2.5 mm throughout the entire procedure. This relatively precise intraoperative feedback led to more accurate recognition of tumor landmarks. It is the authors' impression that a more aggressive resection of these lesions was achieved than could be without the device. We conclude that a frameless stereotactic device such as the ISG Wand is particularly valuable in the approach to skull base and basal cerebral tumors in children.