Image-guided neurosurgery comparing a pointer device system with a navigating microscope: a retrospective analysis of 208 cases.

A retrospective analysis of neuronavigation procedures performed at the Vienna Neurosurgical Clinic was undertaken to elucidate the advantages of 2 technically different navigation systems in clinical use. In a 30-month period, 208 frameless stereotactic procedures were performed using a stereotactic microscope (MKM System, Zeiss; 92 procedures in 87 patients; 47 female, 40 male; mean age, 46 yrs) and a light emitting diode (LED) based pointer navigation device (Easy Guide Neuro (EGN), Philips; 116 procedures in 114 patients; 63 female, 51 male; mean age 46.4 yrs). The navigating microscope was exclusively used for cranial navigation, the pointer device system in 107 cases for cranial and in 9 cases for spinal navigation. Procedures were CCT-guided in 109 cases, MRI-guided in 95, and both CT/MRI guided in 4 cases. Skin fiducials were used in all these procedures. The MKM system provided coordinate-based navigation, similar to frame systems. This allowed surgical planning and performance using stereotactic coordinates for target calculation. Additionally, tumor volumes were defined by contours and projected into the ocular of the microscope, allowing guidance during targeting and resection of lesions. Both of these features proved beneficial in tumor surgery (60.8% MKM cases), cavernoma surgery (21.8% MKM cases), and epilepsy surgery (14.1% MKM cases). In contrast to the microscope, the pointer navigation system could be employed for intuitive correlation of image points with points of interest in the operating field by using a LED-equipped pointer device. This permitted image guidance during a wide spectrum of neurosurgical procedures, in tumor surgery (68.1% EGN cases), cavernoma surgery (5.1% EGN cases), epilepsy surgery (14.1% EGN cases), vascular surgery (3.4% EGN cases), spinal surgery (7.8% EGN cases), and guidance for burr holes and drainages (6.9% EGN cases), without calculating stereotactic coordinates. This analysis showed clear differences in the application of the two systems and may facilitate the decision as to which system best meets the individual demands of a neurosurgical department.