Neurosurgical viewfinder - a simple device for navigation of superficial intracranial lesions: prospective,...

Incorrect position of craniotomy can seriously complicate the course of operation. Frameless navigation stations (FNS) allow accurate craniotomy marking. However, FNS are cumbersome, time consuming, and not accessible to all neurosurgical centers. Our goal is to develop a simple, fast and low-tech method of navigation, and compare its accuracy and working speed with the FNS. The new method includes redrawing the contours of a DICOM image from a computer screen onto a neurosurgical viewfinder (NVF) - a transparent plastic plate; matching the drawn contours with the patient's head, and transferring the lesion contours to the scalp under visual control. NVF was tested on 20 consecutive operations under the control of FNS - first group, and then on another 20 operations without FNS - second group. All 40 patients had convexital or parasagittal lesions extending to the cerebral cortex. The NVF-FNS deviation (mm) and the marking time (minutes) were measured. The craniotomy accuracy was assessed by the centering error (mm) and by the original CRAC (craniotomy accuracy) scale - from 3 to 15 points, the more the better. The NFV-FNS deviation was 2.3 ± 2.2 mm (0 - 7 mm). The mean marking time with the NVF was 4.1 ± 1.1 min, with the FNS - 28.9 ± 5.5 min (p < 0.001). The centering error in the first group was 4.2 ± 5.2 mm (0 - 20 mm); in the second group - 4.1 ± 4.5 mm (0 - 15 mm); the groups did not differ statistically (p = 0.948). The CRAC score also did not differ (p = 0.767) and was not lower than 12 points in both groups. The NVF demonstrated high accuracy, comparable with FNS, and significantly faster marking time. The invention can be widely used in the surgery of convexital and parasagittal lesions.