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Christian Dorfer, Gregor Kasprian, Angelika Mühlebner, and Thomas Czech

Hypothalamic hamartomas are rare lesions for which different classification schemes have been proposed. The authors report on an exceptionally large solid-cystic hamartoma that led to hydrocephalus, precocious puberty, and intractable gelastic seizures. They discuss potential mechanisms of the development of hypothalamic hamartomas.

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Georgi Minchev, Ayguel Wurzer, Wolfgang Ptacek, Gernot Kronreif, Alexander Micko, Christian Dorfer, and Stefan Wolfsberger

OBJECTIVE

Consistently high accuracy and a straightforward use of stereotactic guidance systems are crucial for precise stereotactic targeting and a short procedural duration. Although robotic guidance systems are widely used, currently available systems do not fully meet the requirements for a stereotactic guidance system that combines the advantages of frameless surgery and robotic technology. The authors developed and optimized a small-scale yet highly accurate guidance system that can be seamlessly integrated into an existing operating room (OR) setup due to its design. The aim of this clinical study is to outline the development of this miniature robotic guidance system and present the authors’ clinical experience.

METHODS

After extensive preclinical testing of the robotic stereotactic guidance system, adaptations were implemented for robot fixation, software usability, navigation integration, and end-effector application. Development of the robotic system was then advanced in a clinical series of 150 patients between 2013 and 2019, including 111 needle biopsies, 13 catheter placements, and 26 stereoelectroencephalography (SEEG) electrode placements. During the clinical trial, constant modifications were implemented to meet the setup requirements, technical specifications, and workflow for each indication. For each application, specific setup, workflow, and median procedural accuracy were evaluated.

RESULTS

Application of the miniature robotic system was feasible in 149 of 150 cases. The setup in each procedure was successfully implemented without adding significant OR time. The workflow was seamlessly integrated into the preexisting procedure. In the course of the study, procedural accuracy was improved. For the biopsy procedure, the real target error (RTE) was reduced from a mean of 1.8 ± 1.03 mm to 1.6 ± 0.82 mm at entry (p = 0.05), and from 1.7 ± 1.12 mm to 1.6 ± 0.72 mm at target (p = 0.04). For the SEEG procedures, the RTE was reduced from a mean of 1.43 ± 0.78 mm in the first half of the procedures to 1.12 ± 0.52 mm (p = 0.002) at entry in the second half, and from 1.82 ± 1.13 mm to 1.57 ± 0.98 mm (p = 0.069) at target, respectively. No healing complications or infections were observed in any case.

CONCLUSIONS

The miniature robotic guidance device was able to prove its versatility and seamless integration into preexisting workflow by successful application in 149 stereotactic procedures. According to these data, the robot could significantly improve accuracy without adding time expenditure.

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Christian Dorfer, Arthur Hosmann, Julia Vendl, Irene Steiner, Irene Slavc, Johannes Gojo, Gregor Kasprian, and Thomas Czech

OBJECTIVE

CSF dynamics after transcallosal resection of intraventricular lesions can be altered, and the need for shunt implantation complicates the management of these patients. Because the pathophysiological mechanism and contributing factors are poorly understood and the incidence has largely not been described, the authors conducted a study to elucidate these factors.

METHODS

The authors retrospectively reviewed data from patients who had been operated on at their institution via a transcallosal approach between March 2002 and December 2016. They evaluated the need for a shunt implantation up to 3 months after surgery by assessing clinical variables. These variables were age at surgery, the need for perioperative external CSF drainage, histology of the lesion, and the following radiological parameters: pre- and postoperative Evans index, maximal postoperative extension of subdural effusions (SDEs) measured on axial images, and maximal interhemispheric fissure (IHF) width measured on coronal images assessed at 4 different points in time (preoperatively, day 1, days 2–4, and days 4–8 after surgery). To identify potential risk factors, univariate and multivariate regression models were constructed. Receiver operating characteristic (ROC) curves for significant predictors, as well as the area under the curve (AUC), were calculated.

RESULTS

Seventy-four patients (40 female and 34 male) were identified; their median age at surgery was 17.6 years (range 4 months to 76 years). Shunt implantation was necessary in 13 patients (ventriculoperitoneal [VP] shunt, n = 7; subdural peritoneal [SDP] shunt, n = 6) after a median interval of 24 days (range 10 days to 3 months). Univariate logistic regression models revealed a significant effect of IHF width on days 4–8 (OR 1.31, 95% CI 1.03–1.66; p = 0.027), extension of SDE on days 2–4 (OR 1.33, 95% CI 1.11–1 0.60; p = 0.003), and age (OR 0.932, 95% CI 0.88–0.99; p = 0.02). In the multiple regression model, the effect of the independent variable extension of the SDE remained significant. ROC curves for the predictors IHF width on days 4–8 and extension of SDE on days 2–4 revealed an AUC equal to 0.732 and 0.752, respectively. Before shunt implantation, the ventricles were smaller compared to the preoperative size in 9 of the 13 patients (SDP shunt, n = 5; VP shunt, n = 4).

CONCLUSIONS

The rate of shunt-dependent hydrocephalus 3 months after surgery in this heterogeneous group of patients was 17.6% (95% CI 9.7%–28.2%). The authors identified as predictive factors the variables extension of the convexity space, IHF 1 week after surgery, and younger age.

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Christian Dorfer, Georgi Minchev, Thomas Czech, Harald Stefanits, Martha Feucht, Ekaterina Pataraia, Christoph Baumgartner, Gernot Kronreif, and Stefan Wolfsberger

OBJECTIVE

The authors' group recently published a novel technique for a navigation-guided frameless stereotactic approach for the placement of depth electrodes in epilepsy patients. To improve the accuracy of the trajectory and enhance the procedural workflow, the authors implemented the iSys1 miniature robotic device in the present study into this routine.

METHODS

As a first step, a preclinical phantom study was performed using a human skull model, and the accuracy and timing between 5 electrodes implanted with the manual technique and 5 with the aid of the robot were compared. After this phantom study showed an increased accuracy with robot-assisted electrode placement and confirmed the robot's ability to maintain stability despite the rotational forces and the leverage effect from drilling and screwing, patients were enrolled and analyzed for robot-assisted depth electrode placement at the authors' institution from January 2014 to December 2015. All procedures were performed with the S7 Surgical Navigation System with Synergy Cranial software and the iSys1 miniature robotic device.

RESULTS

Ninety-three electrodes were implanted in 16 patients (median age 33 years, range 3–55 years; 9 females, 7 males). The authors saw a significant increase in accuracy compared with their manual technique, with a median deviation from the planned entry and target points of 1.3 mm (range 0.1–3.4 mm) and 1.5 mm (range 0.3–6.7 mm), respectively. For the last 5 patients (31 electrodes) of this series the authors modified their technique in placing a guide for implantation of depth electrodes (GIDE) on the bone and saw a significant further increase in the accuracy at the entry point to 1.18 ± 0.5 mm (mean ± SD) compared with 1.54 ± 0.8 mm for the first 11 patients (p = 0.021). The median length of the trajectories was 45.4 mm (range 19–102.6 mm). The mean duration of depth electrode placement from the start of trajectory alignment to fixation of the electrode was 15.7 minutes (range 8.5–26.6 minutes), which was significantly faster than with the manual technique. In 12 patients, depth electrode placement was combined with subdural electrode placement. The procedure was well tolerated in all patients. The authors did not encounter any case of hemorrhage or neurological deficit related to the electrode placement. In 1 patient with a psoriasis vulgaris, a superficial wound infection was encountered. Adequate physiological recordings were obtained from all electrodes. No additional electrodes had to be implanted because of misplacement.

CONCLUSIONS

The iSys1 robotic device is a versatile and easy to use tool for frameless implantation of depth electrodes for the treatment of epilepsy. It increased the accuracy of the authors' manual technique by 60% at the entry point and over 30% at the target. It further enhanced and expedited the authors' procedural workflow.

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Georgi Minchev, Gernot Kronreif, Wolfgang Ptacek, Christian Dorfer, Alexander Micko, Svenja Maschke, Federico G. Legnani, Georg Widhalm, Engelbert Knosp, and Stefan Wolfsberger

OBJECTIVE

As decisions regarding tumor diagnosis and subsequent treatment are increasingly based on molecular pathology, the frequency of brain biopsies is increasing. Robotic devices overcome limitations of frame-based and frameless techniques in terms of accuracy and usability. The aim of the present study was to present a novel, minimally invasive, robot-guided biopsy technique and compare the results with those of standard burr hole biopsy.

METHODS

A tubular minimally invasive instrument set was custom-designed for the iSYS-1 robot-guided biopsies. Feasibility, accuracy, duration, and outcome were compared in a consecutive series of 66 cases of robot-guided stereotactic biopsies between the minimally invasive (32 patients) and standard (34 patients) procedures.

RESULTS

Application of the minimally invasive instrument set was feasible in all patients. Compared with the standard burr hole technique, accuracy was significantly higher both at entry (median 1.5 mm [range 0.2–3.2 mm] vs 1.7 mm [range 0.8–5.1 mm], p = 0.008) and at target (median 1.5 mm [range 0.4–3.4 mm] vs 2.0 mm [range 0.8–3.9 mm], p = 0.019). The incision-to-suture time was significantly shorter (median 30 minutes [range 15–50 minutes] vs 37.5 minutes [range 25–105 minutes], p < 0.001). The skin incision was significantly shorter (median 16.3 mm [range 12.7–23.4 mm] vs 28.4 mm [range 20–42.2 mm], p = 0.002). A diagnostic tissue sample was obtained in all cases.

CONCLUSIONS

Application of the novel instrument set was feasible in all patients. According to the authors’ data, the minimally invasive robot-guidance procedure can significantly improve accuracy, reduce operating time, and improve the cosmetic result of stereotactic biopsies.

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Christian Dorfer, Thomas Czech, Susanne Aull-Watschinger, Christoph Baumgartner, Rebekka Jung, Gregor Kasprian, Klaus Novak, Susanne Pirker, Birgit Seidl, Harald Stefanits, Karin Trimmel, and Ekaterina Pataraia

OBJECTIVE

The aim of this study was to present long-term seizure outcome data in a consecutive series of patients with refractory mesial temporal lobe epilepsy primarily treated with transsylvian selective amygdalohippocampectomy (SAHE).

METHODS

The authors retrospectively analyzed prospectively collected data for all patients who had undergone resective surgery for medically refractory epilepsy at their institution between July 1994 and December 2014. Seizure outcome was assessed according to the International League Against Epilepsy (ILAE) and the Engel classifications.

RESULTS

The authors performed an SAHE in 158 patients (78 males, 80 females; 73 right side, 85 left side) with a mean age of 37.1 ± 10.0 years at surgery. Four patients lost to follow-up and 1 patient who committed suicide were excluded from analysis. The mean follow-up period was 9.7 years. At the last available follow-up (or before reoperation), 68 patients (44.4%) had achieved an outcome classified as ILAE Class 1a, 46 patients (30.1%) Class 1, 6 patients (3.9%) Class 2, 16 patients (10.4%) Class 3, 15 patients (9.8%) Class 4, and 2 patients (1.3%) Class 5. These outcomes correspond to Engel Class I in 78.4% of the patients, Engel Class II in 10.5%, Engel Class III in 8.5%, and Engel Class IV in 2.0%. Eleven patients underwent a second surgery (anterior temporal lobectomy) after a mean of 4.4 years from the SAHE (left side in 6 patients, right side in 5). Eight (72.7%) of these 11 patients achieved seizure freedom.

The overall ILEA seizure outcome since (re)operation after a mean follow-up of 10.0 years was Class 1a in 72 patients (47.0%), Class 1 in 50 patients (32.6%), Class 2 in 7 patients (4.6%), Class 3 in 15 patients (9.8%), Class 4 in 8 patients (5.2%), and Class 5 in 1 patient (0.6%). These outcomes correspond to an Engel Class I outcome in 84.3% of the patients.

CONCLUSIONS

A satisfactory long-term seizure outcome following transsylvian SAHE was demonstrated in a selected group of patients with refractory temporal lobe epilepsy.

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Johannes Herta, Fabian Winter, Ekaterina Pataraia, Martha Feucht, Thomas Czech, Barbara Porsche, Ulrike Leiss, Irene Slavc, Andreas Peyrl, Gregor Kasprian, Karl Rössler, and Christian Dorfer

OBJECTIVE

The goal of this study was to evaluate the feasibility, benefit, and safety of awake brain surgery (ABS) and intraoperative language mapping in children and adolescents with structural epilepsies. Whereas ABS is an established method to monitor language function in adults intraoperatively, reports of ABS in children are scarce.

METHODS

A retrospective chart review of pediatric patients ≤ 18 years of age who underwent ABS and cortical language mapping for supratentorial tumors and nontumoral epileptogenic lesions between 2008 and 2019 was conducted. The authors evaluated the global intellectual and specific language performance by using detailed neuropsychological testing, the patient’s intraoperative compliance, results of intraoperative language mapping assisted by electrocorticography (ECoG), and postsurgical language development and seizure outcomes. Descriptive statistics were used for this study, with a statistical significance of p < 0.05.

RESULTS

Eleven children (7 boys) with a median age of 13 years (range 10–18 years) underwent ABS for a lesion in close vicinity to cortical language areas as defined by structural and functional MRI (left hemisphere in 9 children, right hemisphere in 2). Patients were neurologically intact but experiencing seizures; these were refractory to therapy in 9 patients. Compliance during the awake phase was high in 10 patients and low in 1 patient. Cortical mapping identified eloquent language areas in 6/10 (60%) patients and was concordant in 3/8 (37.5%), discordant in 3/8 (37.5%), and unclear in 2/8 (25%) patients compared to preoperative functional MRI. Stimulation-induced seizures occurred in 2 patients and could be interrupted easily. ECoG revealed that afterdischarge potentials (ADP) were involved in 5/9 (56%) patients with speech disturbances during stimulation. None of these patients harbored postoperative language dysfunction. Gross-total resection was achieved in 10/11 (91%) patients, and all were seizure free after a median follow-up of 4.3 years. Neuropsychological testing using the Wechsler Intelligence Scale for Children and the verbal learning and memory test showed an overall nonsignificant trend toward an immediate postoperative deterioration followed by an improvement to above preoperative levels after 1 year.

CONCLUSIONS

ABS is a valuable technique in selected pediatric patients with lesions in language areas. An interdisciplinary approach, careful patient selection, extensive preoperative training of patients, and interpretation of intraoperative ADP are pivotal to a successful surgery.

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Christian Dorfer, Thomas Czech, Angelika Mühlebner-Fahrngruber, Aygül Mert, Gudrun Gröppel, Klaus Novak, Anastasia Dressler, Edith Reiter-Fink, Tatjana Traub-Weidinger, and Martha Feucht

Object

Outcomes following functional hemispherotomy in patients with drug-resistant epilepsy have been well described. However, studies reporting long-term longitudinal outcomes after subhemispheric disconnective epilepsy surgery are still limited.

Methods

The authors conducted a retrospective review of prospectively collected data of 10 children who underwent temporoparietooccipital (TPO) disconnective surgery at the Vienna Pediatric Epilepsy Center.

Results

There were 3 males and 7 females (median age 8.7 years; range 4.2–22.1 years). The affected hemisphere was the left in 3 patients and the right in 7. The patients' median age at seizure onset was 3.0 years (range 0.2–8.3 years). The median duration of epilepsy before surgery was 5.2 years (range 1.3–17.2 years). The underlying pathology was TPO malformation of cortical development in 5 patients, and venous infarction, posterior hemispheric quadrant atrophy, Sturge-Weber syndrome, cortical involvement of a systemic lupus erythematosus, and gliosis after cerebral tumor treatment in 1 each. In 6 children, a pure TPO disconnection was performed; in 2 patients, the temporal lobe was resected and parietooccipital disconnection was performed. The 2 remaining patients had had previous epilepsy surgery that was extended to a TPO disconnection: disconnection of the occipital lobe (n = 1) and resection of the temporal lobe (n = 1). The authors encountered no complications while performing surgery. No patient needed blood replacement therapy. No patient developed CSF disturbances that warranted treatment. Nine of 10 patients are currently seizure free since surgery (Wieser Class 1a) at a median follow-up time of 2.1 years (range 4 months to 8.1 years).

Conclusions

Temporoparietooccipital disconnection is a safe and effective motor-sparing epilepsy surgery in selected cases. Technical adjuncts facilitate a better intraoperative visualization and orientation, thereby enabling a less invasive approach than previously suggested.

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Tatjana Traub-Weidinger, Philip Weidinger, Gundrun Gröppel, Georgios Karanikas, Wolfgang Wadsak, Gregor Kasprian, Christian Dorfer, Anastasia Dressler, Angelika Muehlebner, Marcus Hacker, Thomas Czech, and Martha Feucht

OBJECTIVE

The objective of this study was to investigate whether fluorine-18 fluorodeoxyglucose PET (18F-FDG PET) can help to predict seizure outcome after hemispherotomy and therefore may be useful in decision making and patient selection.

METHODS

Children and adolescents less than 18 years of age who underwent 18F-FDG PET studies during presurgical evaluation prior to hemispherotomy and had follow-up data of at least 12 months after surgery were included. Seizure outcome was classified according to the recommendations of the International League Against Epilepsy. PET data were reevaluated by two specialists in nuclear medicine blinded to clinical data and to MRI. MRI studies were also reinterpreted visually by an experienced neuroradiologist blinded to clinical data and PET findings.

RESULTS

Thirty-five patients (17 girls) with a median age of 5 years (range 0.4–17.8 years) were evaluable. Of the 35 patients, 91.4% were seizure free after surgery, including 100% of those with unilateral 18F-FDG-PET hypometabolism compared with only 75% of those with bilateral hypometabolism. With respect to MRI, seizure freedom after surgery was observed in 96.4% of the patients with unilateral lesions compared with only 71.4% in those with bilateral MRI lesions. The best seizure outcomes were noted in patients with unilateral findings in both PET and MRI (100% seizure freedom) whereas only 50% of those with bilateral findings in both imaging techniques were seizure free. Furthermore, 100% of the patients with unilateral PET hypometabolism and bilateral MRI findings were also seizure free, but only 87.5% of those with bilateral PET hypometabolism and unilateral MRI findings.

CONCLUSIONS

According to these results, candidate selection for hemispherotomy can be optimized by the use of 18F-FDG PET as part of a multimodal presurgical evaluation program, especially in patients with inconsistent (bilateral) MRI findings.

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Anna Cho, Kira Medvedeva, Beate Kranawetter, Helena Untersteiner, Dorian Hirschmann, Olga Lepilina, Anatoly Baulin, Martin Buschmann, Adolf Ertl, Wolfgang Marik, Christian Dorfer, Karl Rössler, Brigitte Gatterbauer, Sergey Ilyalov, and Josa M. Frischer

OBJECTIVE

The authors sought to evaluate clinical outcome in patients with large, high-risk brain metastases (BMs) treated with different dose strategies by use of two-fraction dose-staged Gamma Knife radiosurgery (GKRS).

METHODS

A retrospective analysis was performed with data from 142 patients from two centers who had been treated with two-fraction dose-staged GKRS between June 2015 and January 2020. Depending on the changes in marginal dose between the first (GKRS1) and second (GKRS2) GKRS treatments, the study population was divided into three treatment groups: dose escalation, dose maintenance, and dose de-escalation.

RESULTS

The 142 study patients underwent two-fraction dose-staged GKRS treatments for 166 large, high-risk BMs. The median tumor volume of 7.4 cm3 decreased significantly from GKRS1 to GKRS2 (4.4 cm3; p < 0.001), and to the last follow-up (1.8 cm3; p < 0.001). These significant differences in BM volume reduction were achieved in all three treatment groups. However, differences according to the primary tumor histology were apparent: while dose maintenance seemed to be the most effective treatment strategy for BMs from lung cancer or melanoma, dose escalation was the most beneficial treatment option for BMs from breast, gastrointestinal, or genitourinary cancer. Of note, the vast majority of patients who underwent dose-staged BM treatment did not show any significant postradiosurgical complications.

CONCLUSIONS

In patients with large, high-risk BMs, dose-staged GKRS treatment represents an effective local treatment method with acceptable complication risks. Different dose-strategy options are available that may be chosen according to the primary tumor histology and treatment volume but may also be tailored to the findings at GKRS2.