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Introduction: Infections related to deep brain stimulation (DBS) can lead to discontinuation of the treatment and increased morbidity. Various measures of reducing infection rates have been proposed in the literature, but scientific consensus is lacking. The aim of this study was to report a 26-year single center experience of DBS infections and provide recommendations for the prevention and management of them. Methods: The retrospective analysis consisted of 978 DBS surgeries performed at Oulu University Hospital (OUH) from 1997 to 2022. This included 342 primary or reimplantations of DBS electrodes and 559 primary or reimplantations of implantable pulse generator (IPG). Infections within approximately 1 year after the surgery without secondary cause were considered surgical-site infections (SSIs). χ2 test was used to compare infection rates before and after 2013, when the systematic implementation of infection prevention measures was started. Results: A total of 35 DBS implants were found to be infected. The number of SSIs was 30, of which 29 were originally operated in OUH leading to a center-specific infection rate of 3.1%. Of the SSIs, 17.2% occurred after IPG replacement. Staphylococcus aureus was found in 75.0% of cultures and 32.1% were mixed infections. The treatment of SSIs included aggressive surgical revision combined with cefuroxime and vancomycin antibiotics, as most patients in the initial conservative treatment group eventually required surgical revision. A statistically significant difference in infection rates before and after the implementation of preventative measures was not observed (risk ratio 2.20, 95% confidence interval 0.94–5.75, p = 0.051), despite over two-fold difference in the incidence of SSIs. Conclusion: Our findings show that the rates of surgical infections are low in modern DBS, but due to their serious consequences, preventative measures should be implemented. We highlight that mixed infections should be accounted for in the antibiotic selection. Furthermore, our treatment recommendation includes aggressive surgical revision combined with antibiotic treatment. [ABSTRACT FROM AUTHOR]

Background Sacral neuromodulation operations have usually been performed based on 2D fluoro images. However, sacral nerve stimulation lead implantation may be challenging when the normal anatomy is confused by obesity or congenital anomalies. Thus the surgical navigation and intraoperative imaging methods could be helpful as those same methods have proven to be feasible methods for guiding other surgical operations. Our recent knowledge about the Oarm in trauma pelvic operations encouraged us to evaluate the usefulness of O-arm guided navigation in sacral neuromodulation. Similar navigation would be useful for complex sacral nerve stimulation lead implantations. Methods In this preliminary article we report our experience of utilizing the orthopedically optimized O-arm to implant the S3 stimulation electrode in a patient. The 3D O-arm imaging was performed intraoperatively under surgical navigation control. General anesthesia was used. The obtained 3D image dataset was registered automatically into the patient's anatomy. The stimulation needle was guided and the tined lead electrode was implanted using navigation. Results The bony sacral structures were clearly visualized. Due to automatic registration, the navigation was practicable instantly after the O-arm scanning and operation could be performed successfully under navigation control. Conclusions To our knowledge, this is the first published tined lead implantation which was guided based on the surgical navigation and intraoperative O-arm images. In this case, the applied method was useful and helped the surgeon to demarcate the region of surgical interest. The method is slightly more invasive than the formal technique but could be an option in anatomically challenging cases and reoperations. However, further evaluation with larger patient series is required before definitive recommendations can be made. [ABSTRACT FROM AUTHOR]

Background: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is an approved form of therapy in localization related refractory epilepsy by European authorities and is currently being evaluated for approval by food and drug administration (FDA). Double blind randomized controlled trial (SANTE) showed significant 56% seizure reduction at two years (Fisher et al., 2010). Further improved results with 69% seizure reduction were observed at five years (Salanova et al., 2015). We have recently reported that stimulation site specifically at ANT improves responder rate after ANT-DBS (Lehtimäki et al., 2016). Objective: Here we studied the effect of stimulation site on outcome in more detail focusing on quantitative change in seizures and seizure types with respect to active contact location after ANTDBS. Patients and Methods: Prospective seizure counts from 16 patients with ANT-DBS for refractory epilepsy at Tampere University Hospital were analyzed. A total of 64 DBS lead contacts were stimulated in this patient group to achieve optimal outcome comprising a total of 32 patient years of active stimulation. The location of each contact was evaluated in preoperative 3T MRI STIR images (Möttönen et al., 2015) co-registered with postoperative contrast enhanced CT. Results: In nine patients, initial selected stimulation site was bilaterally at ANT. Seven patients received initially stimulation uni- or bilaterally outside ANT followed by optimization of stimulation site into ANT in five patients by reprogramming and/or surgical replacement (mean delay 31 months). Interestingly, stimulation site bilaterally at ANT was associated with a median of 67% seizure reduction at 24 months compared to baseline (p < 0.05, Wilcoxon signed ranks test) while a median of 21% seizure reduction was observed after non-bilateral stimulation of ANT (p = 0.17). A strong trend towards significant difference between groups at 24 months was observed (p = 0.052; Mann-Whitney test). No significant difference was evident at baseline between patient groups (p = 0.22). However, optimization of the stimulation site into bilateral ANT stimulation in five patients out of seven resulted in improved 60% seizure reduction in this group by last six months carried forward analysis compared to the baseline (p < 0.05; Wilcoxon signed ranks test). Patients with an initial stimulation site bilaterally at ANT showed a median of 92% seizure reduction by last 6 months. The most prominent seizure reduction was observed in seizures with an interruption in awareness (complex partial seizures), while the effect in seizures with preserved awareness (simple partial seizures) or secondarily generalized seizures was modest. Conclusions: Stimulation site at ANT is crucial for therapy response, and favorable outcome may be achieved also relatively late by optimization of the stimulation site by reprogramming or replacement of the leads. Outcome improves clearly over time after chronic bilateral stimulation of ANT being most prominent in seizures with interruption in awareness. [ABSTRACT FROM AUTHOR]

A new application of the projection reconstruction method was developed, enabling dynamic T1-weighted contrast-enhanced magnetic resonance image (MRI) of brain tumors in a low-field imager. Two undersampled projection reconstruction spin echo sequences were implemented in an open low-field (0.23-T) MR imager, one with 64 and another with 42 projections in [0,π], repetition time 150 ms, echotime 15 ms, and six slices were used in both sequences. The possibility of using these sequences to image dynamic contrast enhancement of brain tumors was studied in laboratory experiments and in two patient cases, one with fibrotic and the other with meningothelial meningioma. The laboratory experiments showed a nearly linear response in signal intensity to the concentration of gadopentetate dimeglumine in purified water up to 1.25 mM. Increasing concentrations up to 5.0 mM did not significantly affect the signal intensity, though starting from 3.0 mM concentration T2 shortening decreased intensities slightly. The patient cases showed results consistent with an earlier study performed in a high-field imager. The results show that the studied sequences can be used to follow dynamic contrast enhancement in a low-field imager. [Copyright &y& Elsevier]

The objective of this study was to assess the accuracy of a commercial surgical navigator using optical tracking modality with automated registration between O-arm images and the scanned object. Automated registration was enabled by using the spine navigation software of the navigator. The used phantom was designed by the authors of this paper. The surgical navigators and the O-arm are routinely used at Oulu University Hospital, Oulu, Finland. The distances measured with the surgical navigator from the fixed origin of the phantom were compared to the known phantom accuracy assessment coordinates. The error of the surgical navigator was the difference between measured and true values. The mean displacement error was 0.20 mm with a standard deviation of 0.14 mm. The results show that automated registration is very reliable for image guided surgery (IGS) and that the present accuracy assessment method can be used to periodically check surgical navigator accuracy using O-arm data.

The objective of this study was to design a calibration phantom for a surgical navigator used in a hospital environment. It addresses two major issues: the design of an accuracy phantom and the accuracy analysis of the surgical navigator in a hospital setting. The designed phantom was used to assess the accuracy of the optical tracking modality of the surgical navigator used at Oulu University Hospital, Oulu, Finland. The phantom functioned according to the design criteria, it was easy to use and it had enough calibration points that were localized by the navigator according to the accuracy assessment protocol to assess the accuracy error. The distances measured from a fixed origin with the surgical navigator were compared to the known phantom calibration point coordinates. The mean error was within the manufacturer specifications of 1.00 mm. The analysis done using the designed phantom and accuracy assessment protocol showed that the error increased with the distance from the center of the phantom. The accuracy assessment protocol using the present phantom proved to be a suitable method for accuracy analysis of a surgical navigator in a hospital setting.

Objective: To develop a clinically useful method that shows the corresponding planes of intraoperative two-dimensional ultrasonography and intraoperative magnetic resonance imaging (MRI) scans determined with an optical neuronavigator from an intraoperative three-dimensional MRI scan data set, and to determine the qualitative and the quantitative spatial correspondence between the ultrasonography and MRI scans., Methods: An ultrasound probe was interlinked with an ergonomic and MRI scan-compatible ultrasonography probe tracker to the optical neuronavigator used in a low-field intraoperative MRI scan environment for brain surgery. Spatial correspondence measurements were performed using a custom-made ultrasonography/MRI scan phantom. In this work, instruments to combine intraoperatively collected ultrasonography and MRI scan data with an optical localization method in a magnetic environment were developed. The ultrasonography transducer tracker played an important role. Furthermore, a phantom for ultrasonography and MRI scanning was produced. This is the first report, to our knowledge, regarding the possibility of combining the two most important intraoperative imaging modalities used in neurosurgery, ultrasonography and MRI scanning, to guide brain tumor surgery., Results: The method was feasible and, as shown in an illustrative surgical case, has direct clinical impact on image-guided brain surgery. The spatial deviation between the ultrasonography and the MRI scans was, on average, 1.90 +/- 1.30 mm at depths of 0 to 120 mm from the ultrasonography probe., Conclusion: The overall result of this work is a unique method to guide the neurosurgical operation with neuronavigated ultrasonography imaging in an intraoperative MRI scanning environment. The relevance of the method is emphasized in minimally invasive neurosurgery.