A prospective clinical study for pedicle screw placement with augmented reality surgical navigation including intraoperative 3D imaging in a hybrid operating room was performed in 20 patients of whom 13 had scoliosis. The screw placement accuracy was 94.1% with an average navigation time of 5.4 minutes per screw placement.

This study aimed to compare screw placement accuracy and clinical aspects between Augmented Reality Surgical Navigation (ARSN) and free-hand (FH) technique. Twenty patients underwent spine surgery with screw placement using ARSN and were matched retrospectively to a cohort of 20 FH technique cases for comparison. All ARSN and FH cases were performed by the same surgeon. Matching was based on clinical diagnosis and similar proportions of screws placed in the thoracic and lumbosacral vertebrae in both groups. Accuracy of screw placement was assessed on postoperative scans according to the Gertzbein scale and grades 0 and 1 were considered accurate. Procedure time, blood loss and length of hospital stay, were collected as secondary endpoints. A total of 262 and 288 screws were assessed in the ARSN and FH groups, respectively. The share of clinically accurate screws was significantly higher in the ARSN vs FH group (93.9% vs 89.6%, p < 0.05). The proportion of screws placed without a cortical breach was twice as high in the ARSN group compared to the FH group (63.4% vs 30.6%, p < 0.0001). No statistical difference was observed for the secondary endpoints between both groups. This matched-control study demonstrated that ARSN provided higher screw placement accuracy compared to free-hand.Compared to conventional free-hand (FH) surgical technique, computer-assisted navigation using intraoperative 3D imaging has been shown to improve screw placement accuracy and reduce complications due to screw misplacements 1 . Moreover, improved accuracy has also been shown in more challenging conditions, such as scoliosis surgery, where it may be of even greater importance 2 . Consequently, navigation also reduces the frequency of postoperative revision surgery compared to FH surgery 3 .Although several studies have compared intraoperative image guidance to free-hand (FH) technique, the evidence in favor of navigation is still limited. In a recent systematic review, Chan et al., found only four studies comparing computed tomography (CT) guidance with free-hand methods head-to-head, including one small (10 patients in each group, 169 screws in total) randomized study 4 . Overall, the reviewers found only moderate level evidence showing that CT guidance has lower breach rates than FH, while screw-related complication rates were conflicting at 0% in CT navigation compared with 0%-1.7% in FH groups 5 . In a more recent retrospective study comparing O-arm navigation to FH, Wang et al. demonstrated higher pedicle screw accuracy and lower total

ObjectiveChordomas of the skull base have high recurrence rates even after radical resection and adjuvant radiotherapy. We evaluate the long-term clinical outcome using multidisciplinary management in the treatment of clival chordomas.MethodsBetween 1984 and 2015, 22 patients diagnosed with an intracranial chordoma were treated at the Karolinska University Hospital, Stockholm, Sweden. Sixteen of 22 were treated with Gamma Knife radiosurgery (GKRS) for tumour residual or progression during the disease course. Seven of 22 received adjuvant fractionated radiotherapy and 5 of these also received proton beam radiotherapy.ResultsFifteen of 22 (68%) patients were alive at follow-up after a median of 80 months (range 22–370 months) from the time of diagnosis. Six were considered disease free after >10-year follow-up. The median tumour volume at the time of GKRS was 4.7 cm3, range 0.8–24.3 cm3. Median prescription dose was 16 Gy, range 12–20 Gy to the 40–50% isodose curve. Five patients received a second treatment with GKRS while one received three treatments. After GKRS patients were followed with serial imaging for a median of 34 months (range 6–180 months). Four of 16 patients treated with GKRS were in need of a salvage microsurgical procedure compared to 5/7 treated with conventional or proton therapy.ConclusionAfter surgery, 7/22 patients received conventional and/or photon therapy, while 15/22 were treated with GKRS for tumour residual or followed with serial imaging with GKRS as needed upon tumour progression. With this multidisciplinary management, 5- and 10-year survivals of 82% and 50% were achieved, respectively.

Objective Perineural cysts, also known as Tarlov cysts, are cerebrospinal fluid-filled growths that develop at the intersection of a dorsal root ganglion and posterior nerve root. They are typically an asymptomatic and incidental finding during routine spine imaging. For symptomatic perineural cysts, there is little evidence on which treatment is most effective or when it is indicated. The aim of this study was to review our experience from a population-based cohort of patients with symptomatic perineural cysts and to propose an algorithm that could be used in the selection of surgical candidates. Methods A retrospective review was conducted of all adult (≥ 15 years) patients with symptomatic perineural cysts who were referred to Karolinska University Hospital between 2002 and 2018. Results Thirty-nine patients were included. The most common symptom was sciatica ( n = 22). Cyst aspiration was performed in 28 patients, 24 of whom showed clinical improvement and were offered surgery. Microsurgical cyst fenestration was performed in 17 patients, 16 of whom showed clinical improvement at long-term follow-up. There were no surgical complications. Ten of the patients who were offered surgery chose to be treated conservatively instead, four of whom showed progression of symptoms at long-term follow-up. Conclusions Microsurgical cyst fenestration seems to be a safe and effective option for symptomatic relief in patients with perineural cysts. Based on the results from our series and those of others, we propose an algorithm for the selection of surgical candidates. Electronic supplementary material The online version of this article (10.1007/s00701-019-04000-5) contains supplementary material, which is available to authorized users.

Background:Brain metastases often lead to serious neurological impairment and life threatening states. Their acute management remains complex, particularly in the case of rare malignancies with aggressive evolution. In large single lesions, open surgery followed by radiation to the surgical cavity is widely regarded as the best approach; yet in many cases, microsurgery is not feasible due to the lesion's critical location and/or the number of brain metastases present. We report the effects of adaptive hypofractionated gamma knife radiosurgery in the acute management of critically located thymic carcinoma metastases.Case Description:A 50-year-old male with metastatic thymic carcinoma was treated with radiosurgery for two large supratentorial brain metastases (M3 and M4) adjacent to eloquent areas and one smaller cerebellar metastasis (M2). M3 and M4 were treated with adaptive hypofractionated gamma knife radiosurgery, showing a dramatic volume reduction 4 weeks after treatment completion without radiation-induced side effects. Thirteen months later, two new small, threatening supratentorial lesions (M5-M6) were treated with the same technique. Interestingly, M2 (treated with standard single fraction) and M5-M6 developed local adverse radiation events. The patient's general and neurological status remained next to normal by the time of paper submission.Conclusion:The application of adaptive hypofractionated radiosurgery in this acute setting proved effective in terms of rapid tumor ablation, with salvage of neurological functionality and limited toxicity. We have called the overall procedure rapid rescue radiosurgery (RRR). A systematic study of past and ongoing RRR-treatments is warranted and in progress.