OBJECTIVE

Various techniques are available for stereotactic implantation of depth electrodes for intracranial epilepsy monitoring. The goal of this study was to evaluate the accuracy and effectiveness of frameless MRI-guided depth electrode implantation.

METHODS

Using a frameless MRI-guided stereotactic approach (Stealth), depth electrodes were implanted in patients via burr holes or craniotomy, mostly into the medial temporal lobe. In all cases in which it was possible, postoperative MR images were coregistered to planning MR images containing the marked targets for quantitative analysis of intended versus actual location of each electrode tip. In the subset of MR images done with sufficient resolution, qualitative assessment of anatomical accuracy was performed. Finally, the effectiveness of implanted electrodes for identifying seizure onset was retrospectively examined.

RESULTS

Sixty-eight patients underwent frameless implantation of 413 depth electrodes (96% to mesial temporal structures) via burr holes by one surgeon at 2 institutions. In 36 patients (203 electrodes) planning and postoperative MR images were available for quantitative analysis; an additional 8 procedures with 19 electrodes implanted via craniotomy for grid were also available for quantitative analysis. The median distance between intended target and actual tip location was 5.19 mm (mean 6.19 ± 4.13 mm, range < 2 mm–29.4 mm). Inaccuracy for transtemporal depths was greater along the electrode (i.e., deep), and posterior, whereas electrodes inserted via an occipital entry deviated radially. Failure to localize seizure onset did not result from implantation inaccuracy, although 2 of 62 patients (3.2%)—both with electrodes inserted occipitally—required reoperation. Complications were mostly transient, but resulted in long-term deficit in 2 of 68 patients (3%).

CONCLUSIONS

Despite modest accuracy, frameless depth electrode implantation was sufficient for seizure localization in the medial temporal lobe when using the orthogonal approach, but may not be adequate for occipital trajectories.

OBJECTIVE

The authors sought to compare the dosimetric quality of hypofractionated stereotactic radiosurgery in treating sizeable brain tumors across the following treatment platforms: GammaKnife (GK) Icon, CyberKnife (CK) G4, volumetric modulated arc therapy (VMAT) on the Varian TrueBeam STx, double scattering proton therapy (DSPT) on the Mevion S250, and intensity modulated proton therapy (IMPT) on the Varian ProBeam.

METHODS

In this retrospective study, stereotactic radiotherapy treatment plans were generated for 10 patients with sizeable brain tumors (> 3 cm in longest diameter) who had been treated with VMAT. Six treatment plans, 20–30 Gy in 5 fractions, were generated for each patient using the same constraints for each of the following radiosurgical methods: 1) GK, 2) CK, 3) coplanar arc VMAT (VMAT-C), 4) noncoplanar arc VMAT (VMAT-NC), 5) DSPT, and 6) IMPT. The coverage; conformity index; gradient index (GI); homogeneity index; mean and maximum point dose of organs at risk; total dose volume (V) in Gy to the normal brain for 2 Gy (V2), 5 Gy (V5), and 12 Gy (V12); and integral dose were compared across all platforms.

RESULTS

Among the 6 techniques, GK consistently produced a sharper dose falloff despite a greater central target dose. GK gave the lowest GI, with a mean of 2.7 ± 0.1, followed by CK (2.9 ± 0.1), VMAT-NC (3.1 ± 0.3), and VMAT-C (3.5 ± 0.3). The highest mean GIs for the proton beam treatments were 3.8 ± 0.4 for DSPT and 3.9 ± 0.4 for IMPT. The GK consistently targeted the lowest normal brain volume, delivering 5 to 12 Gy when treating relatively smaller- to intermediate-sized lesions (less than 15–20 cm³). Yet, the differences across the 6 modalities relative to GK decreased with the increase of target volume. In particular, the proton treatments delivered the lowest V5 to the normal brain when the target size was over 15–20 cm³ and also produced the lowest integral dose to the normal brain regardless of the target size.

CONCLUSIONS

This study provides an insightful understanding of dosimetric quality from both photon and proton treatment across the most advanced stereotactic radiotherapy platforms.

OBJECTIVE

The indication for and timing of surgery for epilepsy associated with low-grade mixed neuronal-glial tumors may be controversial. The purpose of this study was to evaluate the effect of resection and associated variables on epilepsy and on progression-free survival (PFS).

METHODS

A retrospective chart review of patients treated between 1992 and 2016 was conducted to identify individuals with epilepsy and low-grade gliomas or neuronal-glial tumors who underwent resective surgery. Data analyzed included age at epilepsy onset, age at surgery, extent of resection, use of electrocorticography, the number of antiepileptic drugs (AEDs) before and after surgery, the presence of dysplasia, Engel class, histological findings, and PFS. The institutional review board protocol was specifically approved to conduct this study.

RESULTS

A total of 107 patients were identified. The median follow-up was 4.9 years. The most common pathology was dysembryoplastic neuroepithelial tumor (36.4%), followed by ganglioglioma (31.8%). Eighty-four percent of patients had Engel class I outcomes following surgery. Gross-total resection was associated with a higher likelihood of an Engel class I outcome (90%) as compared to subtotal resection (58%) (p = 0.0005). Surgery reduced the AED burden, with 40% of patients requiring no AEDs after surgery (p < 0.0001). Children with neurodevelopmental comorbidities (n = 5) uniformly did not experience seizure improvement following resection (0% vs 83% overall; p < 0.0001). Electrocorticography was used in 33% of cases and did not significantly increase class I outcomes. PFS was 90% at 5 years. Eleven percent of tumors recurred, with subtotal resection more likely to result in recurrence (hazard ratio 5.3, p = 0.02). Histological subtype showed no significant impact on recurrence.

CONCLUSIONS

Gross-total resection was strongly associated with Engel class I outcome and longer PFS. Further studies are needed to elucidate the suitable time for surgery and to identify factors associated with oncological transformation.

OBJECTIVE

The aim of this study was to determine the population-based epidemiology of chronic subdural hematoma (CSDH) over a 26-year period.

METHODS

A retrospective study was conducted of all adult patients (≥ 18 years and residents of Pirkanmaa [Finland]) with a diagnosis of CSDH between 1990 and 2015. The cases were identified using ICD codes. Detailed data collection was performed using medical records and death certificates. All patients were monitored until death or the end of year 2017. The annual number of inhabitants in the Pirkanmaa region was obtained from Statistics Finland (Helsinki, Finland).

RESULTS

A total of 1168 patients with CSDH were identified from hospital records and death certificates; patients were considered as new-incidence cases if 2 years had elapsed following primary treatment and in cases involving a new contralateral CSDH. From 1990 to 2015, the overall incidence of CSDH doubled from 8.2 to 17.6/100,000/year. Among adults younger than 70 years, the incidence remained quite stable, whereas the incidence clearly increased among the ≥ 80-year-old population, from 46.9 to 129.5/100,000/year. The median age for a CSDH diagnosis increased from 73 to 79 years during the 26-year period. Head trauma was documented in 59% of cases. A ground-level fall was related to the CSDH in 31% of patients younger than 60 years and in 54% of those 80 years or older. The proportion of alcohol-related cases decreased toward the end of the study period (1990–1995: 16% and 2011–2015: 7%), because alcohol abuse was less frequent among the growing group of elderly patients. In contrast, the percentage of patients receiving anticoagulant or antiplatelet medication almost doubled toward 2015 (1990–1995, 27%; and 2011–2015, 49%). The patients’ neurological condition on admission, based on both Glasgow Coma Scale score (score < 13: 1990–1995, 18%; and 2011–2015, 7%; p < 0.001) and the modified Rankin Scale score (score 0–2: 1990–1995, 8%; and 2011–2015, 19%; p < 0.001), was better in recent years than in the early 1990s.

CONCLUSIONS

From 1990 to 2015, the incidence of CSDH has increased markedly. The incidence of CSDH among the population 80 years or older has nearly tripled since 1990. The use of anticoagulants has increased, but there has been no change regarding the ratio between a traumatic and a spontaneous CSDH etiology. As the world population becomes progressively older, the increasing incidence of CSDH will be a burden to patients and a future challenge for neurosurgical clinics.

OBJECTIVE

The authors conducted a retrospective analysis of a consecutive series of children with intracranial subdural empyemas (SEs) and epidural abscesses (EAs) to highlight the important clinical difference between these two entities. They describe the delays and pitfalls in achieving accurate diagnoses and make treatment recommendations based on clinical and imaging findings.

METHODS

They reviewed their experience with children who had presented with intracranial SE and/or EA in the period from January 2013 to May 2018. They recorded presenting complaint, date of presentation, age, neurological examination findings, time from presentation to diagnosis, any errors in initial image interpretation, timing from diagnosis to surgical intervention, type of surgical intervention, neurological outcome, and microbiology data. They aimed to assess possible causes of any delay in diagnosis or surgical intervention.

RESULTS

Sixteen children with SE and/or EA had undergone evaluation by the authors’ neurosurgical service since 2013. Children with SE (n = 14) presented with unmistakable evidence of CNS involvement with only one exception. Children with EA alone (n = 2) had no evidence of CNS dysfunction. All children older than 1 year of age had sinusitis.

The time from initial presentation to a physician to diagnosis ranged from 0 to 21 days with a mean and median of 4.5 and 6 days, respectively. The time from diagnosis to neurosurgical intervention ranged from 0 to 14 days with a mean and median of 3 and 1 day, respectively. Delay in treatment was due to misinterpretation of images, a failure to perform timely imaging, progression on imaging as an indication for surgical intervention, or the managing clinician’s preference. Among the 14 cases with SE, initial imaging studies in 6 were not interpreted as showing SE. Four SE collections were dictated as epidural even on MRI. The only fatality was associated with no surgical intervention. Endoscopic sinus surgery was not associated with reducing the need for repeat craniotomy.

CONCLUSIONS

Regardless of the initial imaging interpretation, any child presenting with focal neurological deficit or seizures and sinusitis should be assumed to have an SE or meningitis, and a careful review of high-resolution imaging, ideally MRI with contrast, should be performed. If an extraaxial collection is identified, surgical drainage should be performed expeditiously. Neurosurgical involvement and evaluation are imperative to achieve timely diagnoses and to guide management in these critically ill children.

OBJECTIVE

The goal of this study was to develop and validate a system for automatic segmentation of the spine, pedicle identification, and screw path suggestion for use with an intraoperative 3D surgical navigation system.

METHODS

Cone-beam CT (CBCT) images of the spines of 21 cadavers were obtained. An automated model-based approach was used for segmentation. Using machine learning methodology, the algorithm was trained and validated on the image data sets. For measuring accuracy, surface area errors of the automatic segmentation were compared to the manually outlined reference surface on CBCT. To further test both technical and clinical accuracy, the algorithm was applied to a set of 20 clinical cases. The authors evaluated the system’s accuracy in pedicle identification by measuring the distance between the user-defined midpoint of each pedicle and the automatically segmented midpoint. Finally, 2 independent surgeons performed a qualitative evaluation of the segmentation to judge whether it was adequate to guide surgical navigation and whether it would have resulted in a clinically acceptable pedicle screw placement.

RESULTS

The clinically relevant pedicle identification and automatic pedicle screw planning accuracy was 86.1%. By excluding patients with severe spinal deformities (i.e., Cobb angle > 75° and severe spinal degeneration) and previous surgeries, a success rate of 95.4% was achieved. The mean time (± SD) for automatic segmentation and screw planning in 5 vertebrae was 11 ± 4 seconds.

CONCLUSIONS

The technology investigated has the potential to aid surgeons in navigational planning and improve surgical navigation workflow while maintaining patient safety.