A.L. Krivoshapkin, P.A. Semin, E.G. Melidi, V.V. Kanygin, O.V. Golovina
Center of Neurosurgery of the Municipal Department of Public Health, Novosibirsk, Russia
Development of computer technologies and their introduction into medical practice allowed to create absolutely original frameless navigation systems, which do not demand use of bulky devices around a patient's head and allow to get precise information on location of an instrument in an on-line mode.
The goal of the present study was experimental studying of parameters of a neuronavigation system and analyzing clinical effectiveness of neuronavigation in surgery of cerebral mass lesions of different genesis.
Materials and Methods. Experimental study of a neuronavigation system precision was carried out on a plastic phantom of a head with determination of coordination points on its surface and points-targets within it.
We analyzed data of 117 patients, operated with neuronavigation use. They had cerebral tumors (91), vascular malformations (21), arachnoid cysts (2) and brain abscesses (2). There were 58 males and 59 females, aged 2-73 (a mean age of 37.9±14.8). According to localization, the tumors were as follows: deep-lying - 17% (16), convexital - 49% (45), skull base - 34% (31). Histological examination showed, that there were glial tumors (38), meningiomas (20), pituitary adenomas (13), neurinomas (2), metastases (6), other types (13). As for vascular malformations, there were 8 patients with cavernous angiomas (they were localized in brain stem in 2 of them) and 13 cases with AVM. Their grade (Spetzler-Martin) was as follows: grade II - 4; grade III - 5, grade IV - 3 and grade V - 1. It should be noted, that almost a half of patients had high-grade malformations. We chose two statistically comparable groups of patients with formations of non-vascular genesis, who were operated in a sequence. They were represented by 94 cases subject to surgical treatment with use of neuronavigation and 72 cases (a control group), operated without installation of a neuronavigator.
Navigation was carried out with the help of the Voyager SX navigation system (Marconi, USA) and software (Version 7, 2001), developed by Z-KAT (USA). It was based on data of the Picker 5000 spiral computer tomograph (USA), operating in Neurobrain mode with I/V introduction of omnipaque and a step of scanning of 3 mm. Besides, we used the Leica OHS surgery microscope, the CUSA Excel ultrasonic destrustor-aspirator (Valleylab), the Viking neurophysiologic device (Nicolet), the MultiDop2 DWL intraoperative Doppler, rentgenoscope, the Valleylab argon plasmatron and the Storz neuroendoscopic set for performing low-invasive interventions.
Results. The experiment allowed to determine optimum conditions for achieving high precision of the system, characterized by a value of 0.5±0.07 mm. It could be done quite easily by using 3-4 radiographic markers with a distance of 3-5 cm between them. It is important to emphasize, that this precision could be attained only in case of manual installation of a navigation probe. Maximum precision of "hitting" a preselected target in simulation of navigation with rigid fixation of a probe was 0.1 mm. Digital cameras were installed at a distance of 120-150 mm in any projection in relation to a head. Standard changes of a position of an operating table in a navigaton mode did not effect the system precision.
As for clinical practice, a value of mean error was 1.5±0.32 mm. It is sufficient for rather resolute removal of formations with a size of 5 mm and more. Software potentialities allowed to attain precision of less than 1 mm in carrying out frameless stereotactic navigation. The analysis of groups demonstrated a reliable decrease of mortality by 5.8%, reduction of operation time and intraoperative blood loss by 29 min and 453 ml respectively in patients, operated with navigation (p<0.01). Duration of preoperative narcosis, general anesthesia and a period of stay in a resuscitation department had no reliable difference (p>0.05). Puncture aspiration was used for surgical treatment of one deep-lying abscess; the second subcortical abscess, located in eloquent brain area, was removed together with its capsule under navigation control without causing additional neurologic deficit. Endoscopic cystoventriculostomy with navigation guidance was used for surgical treatment of arachnoid cysts. There were no complications. Thanks to neuronavigation guidance, projection craniotomy and exact determination of topical peculiarities of vascular malformations allowed to perform their total removal in all cases. Temporary neurologic deficit with subsequent restoration of functions developed in 3 patients (14%). There was no surgical mortality in the group of cases with vascular malformations.
Conclusions. The results of the experimental study promoted achievement of higher precision of the Voyager SX navigation system in its clinical use. Preoperative planning and intraoperative monitoring of all stages of operation, carried out with the help of the neuronavigator, resulted in a less traumatic character of interventions due to ensuring an optimum approach, reducing a trephination area, performing more radical removal of pathologic lesions within the limits of their boundaries with taking into account localization of eloquent zones and cerebral vessels.