Surgery to monitor and resect epileptogenic foci may be undertaken in 2 stages, providing an opportunity to use skull-fixated fiducials implanted during the first stage to improve the accuracy of cortical resection during the second stage. This study compared the intrinsic accuracy of skin-based and skull-fixated fiducial markers in registering frameless stereotaxy during pediatric epilepsy surgery. To the authors' knowledge, these modalities of registration have not previously been directly compared in this population.
The authors undertook a retrospective review of pediatric patients who underwent resection of epileptogenic foci in 2 stages with frameless stereotactic assistance, performed by a single surgeon at Oregon Health & Science University. For the first stage (subdural grid implantation), 9 skin fiducial markers were used to register anatomical data in a frameless stereotactic station. Intraoperatively, four 3-mm screws were placed circumferentially around the craniotomy. Postoperatively, thin-slice brain MR and CT images were obtained and fused. For the second stage, the 4 screws were used as fiducial markers to register the stereotactic anatomical data. For both stages, accuracy (difference in millimeters from zero of the manual fiducial registration compared with the computer model) was determined using navigation software. The intrinsic accuracy of these 2 methods of fiducial registration was compared using a paired Student t-test.
Between 2004 and 2009, 40 pediatric patients with epilepsy underwent frameless stereotactic surgical procedures. Fourteen patients who had 2-stage procedures using skin-based and skull-fixated registration with complete accuracy data were included in this retrospective review. Mean registration error was significantly lower using skull-fixated fiducials (1.35 mm, 95% CI 1.09-1.60 mm) than using skin-based fiducials (1.85 mm, 95% CI 1.56-2.13 mm; p = 0.0016).
A significantly higher degree of accuracy was achieved using 4 skull-fixated fiducials compared with using 9 skin-based fiducials. This simple and accurate method for registering frameless stereotactic anatomical data does not involve the potential time, expense, discomfort, and morbidity of extraoperative skull-fixated fiducial placement. The method described in this paper could also be extrapolated to other planned 2-stage cranial surgical procedures such as combined skull base approaches.
"Therefore, although these techniques could be considered interesting attempts in reducing pin-related complications, no further consensus can be drawn since the information is based on anecdotal experiences. Other groups have presented their experiences on frameless stereotactic approaches as an alternative to frame-based stereotactic procedures in children    . Head fixation by a drape has also been described . "
[Show abstract][Hide abstract] ABSTRACT: Stereotactic frame-based procedures proved to be precise, safe and are of widespread use among adult patients. Regarding pediatric patients few data is available, therefore the use of the stereotactic frame remains controversial in this population. This motivated us to report our experience in stereotactic procedures in the youngest patients and review the literature concerning this subject.
All frame-based procedures performed in patients younger than seven years in the University of Freiburg during the last 10 years were retrospectively analyzed and discussed under the light of the current literature.
The studied population was composed of 72 patients under the age of seven (mean 3.4 ±2.1 years-old), in whom 99 stereotactic procedures were performed. Brain tumor was present in 60 patients, hydrocephalus in five, cystic lesions in three, intracranial abscess in three and epilepsy in one patient. Stereotactic surgery was performed in 36 cases for brachytherapy, in 29 for biopsy, in 20 cases for cyst puncture, in eight for stereotactically guided endoscopic ventriculostomy, in five for catheter placement and in one case for depth electrode insertion. The overall complication rate was 5%. There were three cases of pin penetration through the skull, one case of frame dislocation after extensive cyst drainage and two skull fractures. Neurologic deficit related to frame fixation was observed in none of the cases. In disagreement with other authors, no case of pin related infection, air embolism, hematoma or CSF leak was observed.
Frame-based stereotactic neurosurgery is a safe technique also in the youngest patients. Rather than the simple use of torque-limiting devices training and experience in the manual adjustment of the stereotactic frame in children have been proven to be crucial factors that contribute to reducing pin related complications.
[Show abstract][Hide abstract] ABSTRACT: Brain biopsies (BB) and depth electrode placements (DEP) are increasingly performed using frameless stereotactic targeting devices. This paper is intended to provide a comprehensive review of the technical features, targeting errors and clinical results.
A PubMed literature search from 1995-2010 was performed.
(A) Modified stereotactic arcs, (B) arm-based devices with and without aiming facilities, and (C) skull affixed devices were found. Guidance technologies were navigation systems (all groups), prospective stereotaxy and custom designed platforms (group C). Mean total errors ranged between 4.4 and 5.4 mm for BB and 2.0 and 3.2 mm for DEP. Diagnostic yield of BB was 89-100%. The clinical success rate for DEP was 96-100%.
Frameless stereotactic targeting devices may reach targeting errors and clinical results comparable with standard frame-based stereotaxy. Advantages and disadvantages of different devices should be acknowledged to ensure optimal technical performance.
International Journal of Medical Robotics and Computer Assisted Surgery 03/2012; 8(1):1-16. DOI:10.1002/rcs.441 · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND:: Neuronavigation has become an intrinsic part of preoperative surgical planning and surgical procedures. However, many surgeons have the impression that accuracy decreases during surgery. OBJECTIVE:: To quantify the decrease of neuronavigation accuracy and identify possible origins, we performed a retrospective quality-control study. METHODS:: Between April and July 2011, a neuronavigation system was used in conjunction with a specially prepared headholder in 55 consecutive patients. Two different neuronavigation systems were investigated separately. Co-registration was performed with laser-surface matching, paired-point matching using skin fiducials, anatomical landmarks, or bone-screws. The initial target registration error (TRE1) was measured using the nasion as the anatomical landmark. Then, after draping and during surgery, the accuracy was checked at predefined procedural landmark steps (MMP=Mayfield measurement point and BMP=bone measurement point), and deviations were recorded. RESULTS:: After initial co-registration, the mean TRE1 was 2.9mm (standard deviation [SD] 3.3). TRE1 was significantly dependent on patient positioning, lesion localization, type of neuroimaging, and co-registration method. The following procedures decreased neuronavigation accuracy: attachment of surgical drapes (□TRE2=2.7mm, SD 1.7), skin-retractor attachment (□TRE3=1.2mm, SD 1.0), craniotomy (□TRE3=1.0mm, SD 1.4), and Halo-ring installation (□TRE3=0.5mm, SD 0.5). Surgery duration was a significant factor too: overall □TRE was 1.3mm (SD 1.5) after 30 minutes and increased up to 4.4mm (SD 1.8) after 5.5 hours of surgery. CONCLUSION:: After registration there is an ongoing loss of neuronavigation accuracy. Major factors were draping, attachment of skin-retractors, and duration of surgery. Surgeons should be aware of this silent loss of accuracy when using neuronavigation.
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