Development and Validation of an Automatic Segmentation Algorithm for Quantification of Intracerebral Hemorrhage.

BACKGROUND AND PURPOSE: ABC/2 is still widely accepted for volume estimations in spontaneous intracerebral hemorrhage (ICH) despite known limitations, which potentially accounts for controversial outcome-study results. The aim of this study was to establish and validate an automatic segmentation algorithm, allowing for quick and accurate quantification of ICH. METHODS: A segmentation algorithm implementing first- and second-order statistics, texture, and threshold features was trained on manual segmentations with a random-forest methodology. Quantitative data of the algorithm, manual segmentations, and ABC/2 were evaluated for agreement in a study sample (n=28) and validated in an independent sample not used for algorithm training (n=30). RESULTS: ABC/2 volumes were significantly larger compared with either manual or algorithm values, whereas no significant differences were found between the latter (P<0.0001; Friedman+Dunn's multiple comparison). Algorithm agreement with the manual reference was strong (concordance correlation coefficient 0.95 [lower 95% confidence interval 0.91]) and superior to ABC/2 (concordance correlation coefficient 0.77 [95% confidence interval 0.64]). Validation confirmed agreement in an independent sample (algorithm concordance correlation coefficient 0.99 [95% confidence interval 0.98], ABC/2 concordance correlation coefficient 0.82 [95% confidence interval 0.72]). The algorithm was closer to respective manual segmentations than ABC/2 in 52/58 cases (89.7%). CONCLUSIONS: An automatic segmentation algorithm for volumetric analysis of spontaneous ICH was developed and validated in this study. Algorithm measurements showed strong agreement with manual segmentations, whereas ABC/2 exhibited its limitations, yielding inaccurate overestimations of ICH volume. The refined, yet time-efficient, quantification of ICH by the algorithm may facilitate evaluation of clot volume as an outcome predictor and trigger for surgical interventions in the clinical setting.

Evaluation of a New Brain Tissue Probe for Intracranial Pressure, Temperature, and Cerebral Blood Flow Monitoring in Patients with Aneurysmal Subarachnoid Hemorrhage.

OBJECTIVE: To evaluate an intraparenchymal probe for intracranial pressure (ICP) and temperature (TEMP) monitoring as well as determination of cerebral hemodynamics using a near-infrared spectroscopy (NIRS) and indocyanine green (ICG) dye dilution method (NIRS-ICP probe). METHODS: The NIRS-ICP probe was applied after aneurysmal subarachnoid hemorrhage if multimodal monitoring was established due to poor neurological condition. ICP and TEMP values were obtained from ventricular catheters and systemic temperature sensors. Repeated NIRS-ICG measurements (2 injections within 30 min) were performed daily for determination of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time of ICG (mttICG). Secondary neurologic dysfunction was defined as brain tissue oxygen tension <20 mmHg and/or lactate/pyruvate ratio >35 obtained from cerebral probing. RESULTS: A total of 128 NIRS-ICG measurements were performed in ten patients. The correlation coefficients between ICP and TEMP values obtained with the NIRS-ICP probe and values from routine monitoring were r = 0.72 and r = 0.96, respectively. The mean values were 30.3 ± 13.6 ml/100 g/min for CBF, 3.3 ± 1.2 ml/100 g for CBV, and 6.8 ± 1.6 s for mttICG. The coefficients of variation from repeated NIRS-ICG measurements were 10.9 % for CBF, 11.7 % for CBV, and 3.8 % for mttICG. The sensitivity for detection of secondary neurologic dysfunction was 85 % and the specificity 83 % using a CBF-threshold of 25 ml/100 g/min. CONCLUSION: Multimodal monitoring using the NIRS-ICP probe is feasible with high reproducibility of measurement values and the ability to detect secondary neurologic dysfunction. No safety concerns exist for the routine clinical use of the NIRS-ICP probe.

Minimally invasive endoscopic surgery for treatment of spontaneous intracerebral haematomas.

Spontaneous intracerebral haemorrhage (ICH) is a devastating disease with a mortality rate of more than 40 % and a high morbidity rate with 10-15 % of survivors remaining fully dependent [11]. The role of surgical treatment of ICH remains a matter of controversy and ongoing investigation. Advances in neurosurgical techniques such as endoscopy and neuronavigation have been established in various fields of neurosurgery. Results of reported case series have suggested that some patients with ICH may benefit from haematoma evacuation through minimally invasive endoscopic procedures. In this article, we focus on the pathophysiologic rationales behind minimally invasive haematoma evacuation through endoscopic surgery and provide an overview of technical developments and reported patient series. In addition, the modalities of the surgical procedure at the authors' institution are described. Controlled clinical trials are needed to evaluate the full potential and limitations of this promising technique.

Perihemorrhagic ischemia occurs in a volume-dependent manner as assessed by multimodal cerebral monitoring in a porcine model of intracerebral hemorrhage.

BACKGROUND: Changes in the perihemorrhagic zone (PHZ) of intracerebral hemorrhage (ICH) are variable. Different mechanisms contribute to secondary neuronal injury after ICH. This multimodal monitoring study investigated early changes in the PHZ of ICH. METHODS: Twenty-four swine were anesthetized, ventilated, and underwent monitoring of vital parameters. Next to an intracranial pressure-probe (ICP), microdialysis (MD), thermodiffusion cerebral blood flow (td-CBF), and oxygen probes (PbrO2) were placed into the gray white matter junction for 12 h of monitoring. ICH was induced using the autologous blood injection model. Pre-defined volumes were 0 ml (sham), 1.5 ml ipsilateral (1.5 ml), 3.0 ml ipsilateral (3.0 ml), and 3.0 ml contralateral (3.0 ml contra). RESULTS: ICP equally increased in all groups after ICH. In the 3.0 ml group tissue oxygenation decreased to ischemic values of 9 ± 7 mmHg early after 6 h of monitoring. This decrease was associated with a significant perfusion reduction from 36 ± 8 ml/100 g/min to 20 ± 10 ml/100 g/min. MD correlated with a threefold lactate/pyruvate ratio increase. Measurements in all other groups were unchanged. CONCLUSION: Multimodal monitoring demonstrates volume-dependent changes of tissue oxygenation, blood flow, and ischemic MD markers in the PHZ independent of increased ICP suggesting early moderate ischemia. No evidence was found for the existence of a perihemorrhagic ischemia in the small hematoma groups.

Decompressive craniectomy in patients with aneurysmal subarachnoid hemorrhage: a single-center matched-pair analysis.

BACKGROUND: The role of decompressive craniectomy (DC) in aneurysmal subarachnoid hemorrhage (aSAH) patients is still controversial. In this study we evaluated the effect of DC for aSAH patients. METHODS: A matched-pair analysis was performed to compare the outcomes of patients with DC to those of patients without DC. Among 295 consecutive aSAH patients, 56 required DC. Of the remaining group, 56 matched controls were found. The match was conducted on the basis of epidemiological and potential prognostic factors, such as age, gender, World Federation of Neurosurgical Societies (WFNS) grade, Fisher group and occurrence of vasospasm. RESULTS: Fifty-four of 56 (96.4%) patients with DC were dependent or dead at 1 month, compared with 49 of 56 (87.5%) without DC. There was no significant difference between the groups (p = 0.16). One-year outcomes were available for 108 patients (96.4%). Thirty-nine of 54 (72.2%) patients treated with DC were dependent or dead at 1 year, compared with 30 of 54 (55.6%) patients in the control group. There was no significant difference between the groups (p = 0.11). This result was unaffected by age, sex and WFNS grade. Subgroup analyses whether DC was performed primarily or delayed, and whether DC was performed due to spasm, hematoma or vessel occlusion failed to detect any significant difference. CONCLUSION: There was no significant advantage for patients treated with DC, but more than 25% achieved a good long-term outcome. While the value of DC is deemed uncertain, it may be effective for a very specific subset of aSAH patients. Further comparative studies are needed to resolve this matter.

Minimally invasive endoscopic surgery for treatment of spontaneous intracerebral hematomas: a single-center analysis.

BACKGROUND: Endoscopic minimally invasive surgery to evacuate ICH has been reported to be more effective than conservative treatment or standard surgical craniotomy. However, most of these reports are based on Asian populations, while European reports do not exist. Here, we, therefore, report our experience from a European neurosurgical stroke center. METHODS: The variables assessed were patient characteristics, technical aspects of surgery, surgical complications, the outcomes grade of hematoma evacuation, 30-day mortality, and functional outcome (defined by modified Rankin Scale, mRS). The mRS was dichotomized into favorable (0-3) and unfavorable outcome (4-6). Mortality was compared to external evidence on conservatively and surgically treated patients by Poisson regression analysis with adjustment for ICH score. RESULTS: Thirty-four patients with ICH were analyzed. The mean age was 62 (standard deviation [SD] 12) years, mean hematoma volume (SD) was 84 (35) ml, and mean time from onset to surgery (SD) was 17 (10) h. Operative times did not exceed 1.5 h. A significant mean hematoma reduction (SD) from 84 (35) ml to 21 (30) ml (p < 0.0001) could be achieved, resulting in a median evacuation rate of 87 %. Early complications related to surgery did not occur. A favorable outcome was observed in 44 % of the patients. Overall, 30-day mortality was 18 %. The relative risk of mortality compared to conventional treatment from other studies was 32 % (95 % confidence interval 23-43 %, p = 0.02). CONCLUSIONS: This European surgical stroke center series of an endoscopic operative technique demonstrates safety and efficacy with regard to reduction of hematoma size in patients with large and space-occupying spontaneous ICH. The study suggests that low mortality and acceptable outcomes may be achievable by minimally invasive hematoma surgery. Whether this technique reduces long-term morbidity compared to standard treatment needs to be further investigated in larger prospective randomized controlled trials.

Evaluating the effects of extended cold ischemia on interstitial metabolite in grafts in kidney transplantation using microdialysis.

PURPOSE: During kidney transplantation (KTx), the length of cold ischemia time (CIT) and the subsequent changes in energy metabolism may lead to variations in interstitial metabolites. Using microdialysis (MD), we evaluated the effects of a short and long CIT on changes of these metabolites. METHODS: Sixteen pigs were randomized in two identical groups, one with a short CIT and the other one with a long CIT. Using MD in the transplanted grafts, we evaluated the parenchyma concentrations of glucose, lactate, pyruvate, glutamate and glycerol in different stages. RESULTS: We noted that during the warm ischemia time (WIT) and in the early post-reperfusion phase glucose levels increased more significantly in the long CIT group and remained high until the end of monitoring. At the end of CIT and during WIT, the long CIT group had a significantly higher glycerol level, but the level dropped gradually in the late post-reperfusion phase and reached a steady state in both groups. CONCLUSIONS: The extended CIT clearly results in considerably impaired graft metabolism. The high interstitial glucose levels within hours after KTx could be considered as a marker of primary delayed function of the graft. Furthermore, the glycerol value could reflect the extent of graft injury during the ischemia time or in case of acute impairment of graft perfusion.

Cortical spreading depression dynamics can be studied using intrinsic optical signal imaging in gyrencephalic animal cortex.

OBJECTIVE: The aim of this study was to co-record electrical changes using electrocorticography (ECoG) and blood volume changes using intrinsic optical signal (IOS) imaging during the induction, propagation, and termination of cortical spreading depolarizations (CSDs). METHODS: Anesthetized male swine were craniotomized and monitored over 16-20 h. A ten-contact electrode strip was placed on the cortex of one hemisphere for ECoG. An optical imaging recording was implemented using a camera with an optical bandpass filter (564 nm, FWHM:15 nm) and a full spectrum light source. CSDs were induced by mechanical and KCl stimulation. Co-occurrences of ECoG baseline shifts and blood volume changes around electrodes were identified. RESULTS: A mean of 3 CSDs per hour were induced, in a total of 4 swine during 80 h of recording. The propagation of the CSDs increased progressively over the monitoring time. IOS enabled us to clearly visualize the induction, propagation, and termination of CSDs with a spatial resolution within the sub-millimeter range. Every CSD recorded using ECoG could also be observed in IOS imaging, although some blood volume changes of CSDs were observed that terminated before reaching any of the ECoG electrodes. CONCLUSION: IOS imaging enables an in vivo evaluation of CSD dynamics over a large surface of gyrencephalic brain.

Using microdialysis for early detection of vascular thrombosis after kidney transplantation in an experimental porcine model.

BACKGROUND: In kidney transplantation (KTx), vascular thrombosis has a major impact on morbidity and graft survival. The ischaemia, caused by thrombosis, can lead to interstitial metabolite changes. The aim of this experimental study was to create conditions in which the graft would be prone to vascular thrombosis following KTx and then to evaluate the role of microdialysis (MD) for its early detection. METHODS: Sixteen randomized pigs in the control group received heparin and immunosuppressive drugs, while the case group received none. Based on histopathological evidence of vascular thrombosis, the case group was subdivided into mildly and severely congested subgroups. Using MD, we evaluated the interstitial concentrations of glucose, lactate to pyruvate ratio, glutamate and glycerol in the transplanted grafts during different phases of KTx. RESULTS: Following reperfusion, we noted considerable changes. The severely congested subgroup showed a low and decreasing level of glucose. Only in this group did the lactate to pyruvate ratio continue to increase until the end of monitoring. The glycerol level increased continuously in the entire case group and this increase was most significant in the severely congested subgroup. In all of the study groups, glutamate concentration remained in a low steady state until the end of monitoring. CONCLUSION: MD can be an appropriate method for early detection of vascular complications after KTx. Decreasing glucose levels, increased lactate to pyruvate ratio and increased glycerol levels are appropriate indicators for early detection of vascular thromboses following KTx. Particularly, the glycerol level could predict the necessity and urgency of intervention needed to ultimately save the transplanted kidney.

Intracranial pressure telemetry: first experience of an experimental in vivo study using a new device.

OBJECTIVE: To test two new telemetric intracranial pressure (ICP) probes (NEUROVENT(®)-P-tel, NEUROVENT(®)-S-tel) in a porcine model. We aimed to intraoperatively correlate the telemetric probes to parenchymal ICP probes and study their reliability in the first hours after implantation. The experimental set-up, new telemetric technology and first data will be presented. METHODS: We implanted a right parietal (parenchymal) and left parietal (subdural) telemetric ICP probe in 13 Göttingen mini-pigs under general anaesthesia. Through the left parietal burr hole a parenchymal ICP probe (Neurovent(®) ICP) was introduced. Intraoperatively, the head position was changed to provoke ICP changes every 10 min. The telemetric probes were left in situ and finally the parenchymal ICP probe was removed. We correlated mean differences between each telemetric probe and the conventional ICP measurement and Bland-Altman plots were generated for statistical analysis. RESULTS: We present first data containing intraoperative measurements of 26 telemetric probes after implantation. Intraoperatively, mean differences of 2.48 ± 1.52 mmHg SD (NEUROVENT(®)-P-tel) and 2.64 ± 1.79 mmHg (NEUROVENT(®)-S-tel) were observed. The Bland-Altman plot demonstrates good correlation of the telemetric probes compared with parenchymal ICP probes. CONCLUSION: We present a new telemetric technology that was experimentally compared with a parenchymal ICP probe. We provide data that the new telemetric probes will comparably measure ICP vs an external ICP probe. This stand-alone ICP tool may allow permanent measurement of ICP in hydrocephalus patients. Further continuation of our study will demonstrate whether this system guarantees acceptable long-term reliability.

Telemetric ICP measurement with the first CE-approved device: data from animal experiments and initial clinical experiences.

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic(®) NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedic's NEUROVENT(®) P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.

Evidence of spreading depolarizations in a porcine cortical intracerebral hemorrhage model.

OBJECTIVES: To evaluate whether cortical spreading depolarizations (CSD) occur in the early stage after cortical intracerebral hemorrhage (ICH). METHODS: Ten anesthetized male swine were examined over 19 h. Two cerebral probes were inserted around the ICH (microdialysis and thermodiffusion cerebral blood flow), ICP was monitored contralaterally and up to two electrocorticographic grid electrodes were positioned over the hemisphere after hemicraniectomy and dural opening. A right frontal autologous, arterial ICH (3.0 mL) was induced in all the animals studied. RESULTS: Using a modified injection technique an 80% success rate in ICH formation could be achieved. Eight animals with cortical ICH could be analyzed finally. After induction of ICH, ICP increased non-significantly. Overall, six out of eight animals had CSDs, of either single type or clusters. In one animal a CSD occurred as early as 2 h after ICH; in all other animals the first CSD did not occur before 5 h after onset. CONCLUSION: CSD's occur in cortical experimental ICH. As ICP remained stable owing to the hemicraniectomy we cannot argue in favor of ICP-related triggering of CSD. Modifications of the experimental setup avoiding hemicraniectomy may better describe the pathophysiology of CSD related to ICH in future studies.

Pressure reactivity index correlates with metabolic dysfunction in a porcine model of intracerebral hemorrhage.

OBJECTIVE: We correlated oxygen, flow, and pressure indices of cerebrovascular reactivity (CR) with extracellular cerebral metabolite concentrations in a porcine model of intracerebral hemorrhage (ICH). METHODS: Continuous advanced multimodal monitoring including microdialysis, cerebral blood flow and P(br)O(2) probes were placed 1 cm in front of the coronal suture in the grey/white matter junction. Following a period of 1 h of monitoring, an autologous arterial ICH with defined volumes (3 mL) was induced. Pressure-, oxygen-, and flow-related autoregulation indices (PRx, ORx, and FRx) were simultaneously calculated and correlated hourly with extracellular cerebral metabolites, including glucose, lactate, pyruvate, and glutamate. RESULTS: Seventeen swine were monitored on average 12 continuous hours per animal. FRx correlated highly with ORx (0.96, P = <0.001), but values of both FRx and ORx > 0.2 did not correlate with any microdialysis metabolite. Values of PRx > 0.2 correlated highly (0.65, P < 0.001) with the lactate/pyruvate ratio, values of PRx > 0.3 correlated with glutamate (0.67, P < 0.05), the lactate/pyruvate ratio (0.60, P < 0.01), and P(br)O(2) (-0.65, P < 0.01). CONCLUSIONS: We found evidence for impaired CR in a porcine model of ICH. The findings suggest that, among other parameters of CR, positive PRx coefficients have the highest significance and could be associated with microdialysis alterations during hypoxic events.

Endoscopic intra-hematomal evacuation of intracerebral hematomas - a suitable technique for patients with coagulopathies.

OBJECTIVES: To describe an endoscopic technique to evacuate acute intracerebral hemorrhage (ICH) using the balanced suction-irrigation method in patients with intrinsic or iatrogenic coagulopathies. METHODS: We report on our early experience with four patients with atypical ICH related to intrinsic and iatrogenic coagulopathies. In all patients, an endoscopic hematoma evacuation was performed using a navigated burrhole approach. The entry site and trajectory were planned according to the long axis of the hematoma. RESULTS: Every operation was carried out with the aid of neuronavigation. Gross total removal of the hematoma was not intended as first line, especially if eloquent areas could be avoided. Intra-hematomal evacuation leaving minimal hematoma remnants was performed in three of four patients. We report hematoma removal rates of approximately 90%. In all patients, a significant hematoma reduction was achieved, although residues were tolerated to limit neurological damage. No re-hemorrhage was observed. CONCLUSION: The endoscopic technique with the aid of neuronavigation may be an appropriate method to safely evacuate ICH in the acute stage in patients with intrinsic or iatrogenic coagulopathies.

Multiparametric characterisation of the perihemorrhagic zone in a porcine model of lobar ICH.

OBJECTIVES: To describe early perihemorrhagic changes after lobar intracerebral hemorrhage (ICH) using multiparametric neuromonitoring [intracranial pressure (ICP), cerebral blood flow (CBF), tissue oxygenation (PbrO2), microdialysis (MD)]. METHODS: Seven anaesthetized male swine were examined over 12 h. Four cerebral probes were inserted around the ICH (ICP, MD, CBF and PbrO2). A right frontal autologous arterial ICH (1.5 mL) was induced in all animals. RESULTS: Initial ICH creation was hampered by using a soft 22-G cannula. A modified injection technique with a 90° bent steel cannula (20 G) allowed for an 87.5% success rate in ICH formation. After induction of ICH, ICP significantly increased from 2 mmHg to 9 mmHg. No significant PbrO2 or CBF reduction occurred during the monitoring period. Consequently, microdialysis did not indicate overall mean deterioration in the hematoma group over time. The indicator of ischemia (extracellular lactate) did not increase significantly during the monitoring period. Individual monitoring episodes demonstrated hypoxic episodes with consecutive metabolic derangement. These effects were reversible by optimizing CPP and FiO2. CONCLUSION: We established a reproducible cortical ICH model using multiparametric neuromonitoring. Subtle changes in ICP were observed. No evidence for the existence of a perihemorrhagic ischemic area was found, hypothetically because of the small hematoma size. Individual animals underwent critical PbrO2 and CBF decreases with consecutive metabolic derangement. The effect of larger hematoma volumes should be evaluated with this setup in future studies to study volume-dependent deterioration.

Low-frequency sampling for PRx calculation does not reduce prognostication and produces similar CPPopt in intracerebral haemorrhage patients.

BACKGROUND: The cerebral pressure reactivity index (PRx) correlates with the outcome in intracerebral haemorrhage (ICH) patients and has been used to define an autoregulation-oriented "optimal cerebral perfusion pressure" (CPPopt). PRx has been calculated as a moving correlation coefficient between mean arterial pressure (MAP) and intracranial pressure (ICP) averaged over 5-10 s, using a 2.5- to 5-min moving time window, in order to reflect changes in MAP and ICP within a time frame of 20 s to 2 min. We compared PRx with a different calculation method [low-frequency PRx (L-PRx)], where rapid fluctuations of MAP and ICP are cancelled (waves with frequencies greater than 0.01 Hz). METHODS: A total of 548.5 h of artefact-free data (sampling frequency 1 Hz) from 18 patients suffering from non-traumatic ICH were included in the analysis. L-PRx was calculated using minute averages, between both MAP and ICP, in 20-min moving correlation windows. CPPopt was calculated based on PRx and on L-PRx. RESULTS: The averaged PRx values for each patient correlated with L-PRx (P = 0.846, p < 0.001). CPPopt based on standard PRx was identified in eight patients. In contrast, a CPPopt value based on L-PRx could be found in 12 patients. CPPopt values by both methods correlated strongly with each other (P = 0.980, p < 0.001). L-PRx had a similar correlation with the National Institutes of Health Stroke Scale Score (NIHSS) (0.667, p = 0.002) as did PRx (0.563, p = 0.015). CONCLUSIONS: L-PRx correlated with the outcome as good as PRx did. CPPopt could be identified in more patients using L-PRx. Slower MAP and ICP changes (in the range of 1-20 min) can be used for autoregulation assessment and contain important prognostic information.

Novel oncogene amplifications in tumors from a family with Li-Fraumeni syndrome.

Li-Fraumeni syndrome (LFS) represents an inherited tumor syndrome that is typically caused by germline mutations of the tumor suppressor gene TP53. TP53 dysfunction secondarily disturbs the genetic integrity of the cell. Here, we report a family with LFS harboring a germline TP53 mutation (R248W) located in the functional domain of the protein that binds to the minor groove of the DNA. In this family, tumors of the central nervous system were diagnosed as primary malignancies in all carriers of the mutation. The index patient developed an anaplastic medulloblastoma with unusual genomic profile exhibiting six distinct high-level genomic amplifications, two of them targeting the MYCN and GLI2 genes, respectively. In an extrarenal rhabdoid tumor from the same patient, we found a novel high-level amplification of the MYC oncogene. The father of this patient was diagnosed with myxopapillary ependymoma (WHO degrees I), whereas a brother died from an early relapse of a choroid plexus carcinoma. The analysis of this LFS familiy thus revealed novel oncogene amplifications as different second hits that are likely to also play a role in the pathogenesis of their sporadic counterparts.

Characteristics of thoracolumbar intramedullary subependymomas.

OBJECT: Thoracolumbar intraspinal subependymomas are very rare intramedullary low-grade tumors. The authors report on the clinical and morphological features of 2 cases of thoracolumbar intraspinal subependymomas and provide midterm follow-up data. METHODS: The clinical and radiological profiles of 2 patients with progressive spinal cord dysfunction due to thoracolumbar intraspinal subependymomas were retrospectively studied and compared with previously reported cases. RESULTS: Patients with intraspinal subependymomas initially presented with back pain and long-tract signs. The tumors were hyperintense on T2-weighted MR imaging, isointense on T1-weighted imaging, and noncontrast enhancing. Within 1 of the tumors, a medial septum was present on axial T2-weighted imaging. The tumors were intramedullary but grew exophytically and were amenable to gentle surgical separation from normal neural structures. Therefore, gross-total resection was feasible, and neurological outcome was good. No further adjuvant therapy was conducted. On follow-up (at 58 and 18 months, respectively), no tumor recurrence was observed. CONCLUSIONS: Symptomatic thoracolumbar intraspinal subependymomas with a distinct appearance on MR imaging are amenable to complete excision with favorable neurological outcome. In this study no tumor recurrence was observed at midterm follow-up in either patient, neither of whom underwent adjuvant therapy.

Mini Screws for Improving Accuracy in Navigation-assisted Spine Surgery.

STUDY DESIGN: Presentation of a surgical technique with accompanying video (Supplemental Digital Content 1, http://links.lww.com/CLINSPINE/A67) of an illustrative case. OBJECTIVE: The objective of this study was to present a helpful and easy-to-implement technique for improving initial referencing accuracy, as well as rereferencing accuracy in cases of multilevel instrumentation or in cases of dislocation of the reference array. SUMMARY OF BACKGROUND DATA: Navigation-assisted spine surgery has become standard of care in most hospitals performing complex spine interventions. Although short-segment instrumentations are fairly straight-forward with current hardware and software solutions, obtaining ideal accuracies and troubleshooting reference array disruptions remain challenging. METHODS: A surgical technique is presented as a step-by-step guide using intraoperative videos and photographs as well as imaging data in an illustrative case of thoracic hemivertebra resection and dorsal instrumentation. TECHNIQUE/RESULTS: After skin incision is performed at the index level, posterior soft tissue preparation is performed. Before firmly attaching the reference array to a spinous process we then insert a minimum of four 5 mm mini screws at any bony structure within the exposure. Then an intraoperative navigation scan (3-dimensional computed tomography or x-ray) is obtained, and initial referencing is performed using the previously inserted mini screws as landmarks. This yields mean accuracies of 1 mm or lower and is easily verifiable by placing the navigation probe on a mini screw head. This action can be swiftly repeated at any time to prevent reduced accuracy because of insertion forces applied during pedicle screw placement. In addition, this allows for easy rereferencing in cases of disruption or complete removal of the navigation array, eliminating the need to perform additional computed tomography or x-ray scans during the procedure. CONCLUSIONS: The technique presented allows for rapid and highly accurate initial referencing and can be used in all cases of navigation-assisted spine surgery. It also allows for hassle-free rereferencing in cases of disruption or accidental removal of the reference array.

Risk Factors and Management of Incidental Durotomy in Lumbar Interbody Fusion Surgery.

STUDY DESIGN: This is a retrospective study analysis. OBJECTIVE: In this retrospective study we evaluated risk factors for incidental durotomy and its impact on the postoperative course. SUMMARY OF BACKGROUND DATA: Lumbar interbody fusion (LIF) is increasingly applied for the treatment of degenerative instability. A known complication is incidental durotomy. MATERIALS AND METHODS: A cohort of 541 patients who underwent primary LIF surgery between 2005 and 2015 was analyzed. Previous lumbar surgery, age, surgeon's experience, intraoperative use of a microscope, and the number of operated levels were assessed and the risk for incidental durotomy was estimated using the Log-likelihood test and Wald test, respectively. The association of incidental durotomy and outcome parameters was analyzed using the quantile regression model. RESULTS: In 77 (14.2%) patients intraoperative cerebrospinal fluid (CSF) fistula was observed. Previous lumbar surgery (P<0.001), number of operated levels (P=0.03), and surgeon's experience (P=0.01) were significantly associated with incidental durotomy. Incidental durotomy was significantly associated with a prolonged bed rest (P<0.001), hospital stay (P=0.041), and an increased use of postoperative antibiotics (P<0.001). Eleven of 77 patients with incidental durotomy (14.3%) developed postoperative CSF fistula of whom 10 (91%) needed revision surgery for dural repair. CONCLUSIONS: We could identify important risk factors for incidental durotomy in LIF surgery. In patients who had undergone previous lumbar surgery and those with multilevel disease particular precaution is required. Furthermore, we were able to verify the morbidity associated with CSF fistula as shown by increased immobilization and follow-up surgeries for postoperative CSF fistula which emphasizes the importance to develop strategies to minimize the risk for incidental durotomy.