Author: cba

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Long-term pain outcomes in elderly patients with trigeminal neuralgia: comparison of first-time microvascular decompression and stereotactic radiosurgery

Neurosurg Focus 49 (4):E23, 2020

Common surgical treatments for trigeminal neuralgia (TN) include microvascular decompression (MVD) and stereotactic radiosurgery (SRS). The use of MVD in elderly patients has been described but has yet to be prospectively compared to SRS, which is well-tolerated and noninvasive. The authors aimed to directly compare long-term pain control and adverse event rates for first-time surgical treatments for idiopathic TN in the elderly.

METHODS A prospectively collected database was reviewed for TN patients who had undergone treatment between 1997 and 2017 at a single institution. Standardized collection of preoperative demographics, surgical procedure, and postoperative outcomes was performed. Data analysis was limited to patients over the age of 65 years who had undergone a first-time procedure for the treatment of idiopathic TN with at least 1 year of follow-up.

RESULTS One hundred ninety-three patients meeting the study inclusion criteria underwent surgical procedures for TN during the study period (54 MVD, 24 MVD+Rhiz, 115 SRS). In patients in whom an artery was not compressing the trigeminal nerve during MVD, a partial sensory rhizotomy (MVD+Rhiz) was performed. Patients in the SRS cohort were older than those in the MVD and MVD+Rhiz cohorts (mean ± SD, 79.2 ± 7.8 vs 72.9 ± 5.7 and 70.9 ± 4.8 years, respectively; p < 0.0001) and had a higher mean Charlson Comorbidity Index (3.8 ± 1.1 vs 3.0 ± 0.9 and 2.9 ± 1.0, respectively; p < 0.0001). Immediate or short-term postoperative pain-free rates (Barrow Neurological Institute [BNI] pain intensity score I) were 98.1% for MVD, 95.8% for MVD+Rhiz, and 78.3% for SRS (p = 0.0008). At the last follow-up, 72.2% of MVD patients had a favorable outcome (BNI score I–IIIa) compared to 54.2% and 49.6% of MVD+Rhiz and SRS patients, respectively (p = 0.02). In total, 0 (0%) SRS, 5 (9.3%) MVD, and 1 (4.2%) MVD+Rhiz patients developed any adverse event. Multivariate Cox proportional hazards analysis demonstrated that procedure type (p = 0.001) and postprocedure sensory change (p = 0.003) were statistically significantly associated with pain control.

CONCLUSIONS In this study cohort, patients who had undergone MVD had a statistically significantly longer duration of pain freedom than those who had undergone MVD+Rhiz or SRS as their first procedure. Fewer adverse events were seen after SRS, though the MVD-associated complication rate was comparable to published rates in younger patients. Overall, the results suggest that both MVD and SRS are effective options for the elderly, despite their advanced age. Treatment choice can be tailored to a patient’s unique condition and wishes.

 

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Avoiding New Biopsies by Identification of IDH1 and TERT Promoter Mutation in Nondiagnostic Biopsies From Glioma Patients

Neurosurgery (87): E513–E519

Biopsies in patients with a suspected glioma are occasionally nondiagnostic.

OBJECTIVE: To explore the utility of molecular testing in this setting by determining whether IDH1 and TERT promoter (pTERT) mutations could be detected in nondiagnostic biopsies from glioma patients. METHODS: Using SNaPshot polymerase chain reaction, we retrospectively assessed IDH1 and pTERT mutation status in nondiagnostic biopsies from 28 glioma patients.

RESULTS: The nondiagnostic biopsy (needle biopsy n = 25, open or endoscopic biopsy n = 3) consisted of slight glial cell hypercellularity, hemorrhage, and/or necrosis. After another biopsy (n = 23) or a subsequent surgical resection (n = 5) the diagnosis was an IDH1-wildtype (WT) pTERT-mutant glioma (glioblastoma n = 16, astrocytoma n = 4), an IDH1-mutant pTERT-mutant oligodendroglioma (n = 1), an IDH1-mutant pTERT-WT astrocytoma (n = 1), and an IDH1-WT pTERT-WT glioblastoma (n = 6). An IDH1 mutation was identified in the nondiagnostic biopsies of the 2 IDH-mutant gliomas, and a pTERT mutation in the nondiagnostic biopsies of 16 out of the 21 of pTERTmutant-gliomas (76%). Overall, an IDH1 and/or a pTERT mutation were detected in 17 out of 28 (61%) of nondiagnostic biopsies. Retrospective analysis of the nondiagnostic biopsies based on these results and on imaging characteristics suggested that a new biopsy could have been avoided in 6 patients in whom a diagnosis of “molecular glioblastoma” could have been done with a high level of confidence.

CONCLUSION: In the present series, IDH1 and pTERT mutations could be detected in a high proportion of nondiagnostic biopsies from glioma patients. Molecular testing may facilitate the interpretation of nondiagnostic biopsies in patients with a suspected glioma.

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Single center experiences with telemetric intracranial pressure measurements in patients with CSF circulation disturbances

Acta Neurochirurgica (2020) 162:2487–2497

Hydrocephalus may present with heterogeneous signs and symptoms. The indication for its treatment and the optimal drainage in complex cases may be challenging. Telemetric intracranial pressure measurements (TICPM) may open new perspectives for those circumstances. We report our experiences using the Neurovent-P-tel and the Sensor Reservoir in a retrospective study.

Methods A series of 21 patients (age range 10–39.5 years) treated in our Pediatric Neurosurgical Unit receiving a TICPM was analyzed. In 8 patients, a Neurovent-P-Tel was implanted; 13 patients received a Sensor Reservoir, 6 of which as a stand-alone implant, while 7 were already shunted. TICPM were performed on an outpatient basis. Possible complications, follow-up surgeries, and TICPM were analyzed.

Results Concerning the complications, one infection was seen in each group and one postoperative seizure was observed in the Ptel group. TICPM-assisted shunt adjustments lead to clinical improvements in six patients in the P-tel group and six patients in the Sensor Reservoir group. In four out of six non-shunted patients, TICPMcontributed to the indication toward shunt implantation.

Conclusions TICPM seems to be a promising tool to improve clinical management of shunted patients with complex hydrocephalus. The two available systems will need further technical improvements, concerning implantation time, measurements, and data analysis in order to optimize handling and interpretation of the data.

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Assessment of drainage techniques for evacuation of chronic subdural hematoma

J Neurosurg 133:1113–1119, 2017

Surgery for chronic subdural hematoma (CSDH) is one of the most common neurosurgical procedures. The benefit of postoperative passive subdural drainage compared with no drains has been established, but other drainage techniques are common, and their effectiveness compared with passive subdural drains remains unknown.

METHODS In Scandinavian population-based cohorts the authors conducted a consecutive, parallel cohort study to compare different drainage techniques. The techniques used were continuous irrigation and drainage (CID cohort, n = 166), passive subdural drainage (PD cohort, n = 330), and active subgaleal drainage (AD cohort, n = 764). The primary end point was recurrence in need of reoperation within 6 months of index surgery. Secondary end points were complications, perioperative mortality, and overall survival. The analyses were based on direct regional comparison (i.e., surgical strategy).

RESULTS Recurrence in need of surgery was observed in 18 patients (10.8%) in the CID cohort, in 66 patients (20.0%) in the PD cohort, and in 85 patients (11.1%) in the AD cohort (p < 0.001). Complications were more common in the CID cohort (14.5%) compared with the PD (7.3%) and AD (8.1%) cohorts (p = 0.019). Perioperative mortality rates were similar between cohorts (p = 0.621). There were some differences in baseline and treatment characteristics possibly interfering with the above-mentioned results. However, after adjusting for differences in baseline and treatment characteristics in a regression model, the drainage techniques were still significantly associated with clinical outcome (p < 0.001 for recurrence, p = 0.017 for complications).

CONCLUSIONS Compared with the AD cohort, more recurrences were observed in the PD cohort and more complications in the CID cohort, also after adjustment for differences at baseline. Although the authors cannot exclude unmeasured confounding factors when comparing centers, AD appears superior to the more common PD.

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Treatment for secondary deterioration in idiopathic normal pressure hydrocephalus in the later course of the disease

Acta Neurochirurgica (2020) 162:2431–2439

Cerebrospinal fluid (CSF) shunting is a highly effective treatment for idiopathic normal pressure hydrocephalus (iNPH). However, secondary deterioration can occur at a later time. Thus, the current study aimed to evaluate the incidence rate and causes of secondary deterioration.

Methods A retrospective analysis was conducted on all patients with iNPH who were treated with implantation of a CSF shunt since 1993. A meticulous shunt workup was recommended to all patients who presented to our department with secondary deterioration during their follow-up visits. Data about the proportion of patients with such deterioration and its causes, subsequent treatment, and clinical outcome were obtained.

Results A total of 169 patients were included, and the mean follow-up time was 69.2 months. In total, 119 (70.4%) patients presented with a total of 153 secondary deteriorations. In 9 cases (5.9%), the deterioration was caused by delayed subdural hematoma and in 27 (22.1%) cases, by shunt dysfunction. Invasive shunt testing was commonly required to validate shunt failure. Moreover, 19 of 27 patients experienced a satisfactory improvement after revision surgery. In total, 86 deteriorations were attributed to nonsurgical causes, and the valve pressure was decreased in 79 patients, with only 16.5% presenting with a satisfactory improvement after lowering of valve pressure.

Conclusions Most patients with shunted iNPH presented with deterioration in the later course of the disease. Shunt dysfunction was considered a cause of secondary deterioration. Moreover, shunt revision surgery was a highly effective treatment, and patients with deterioration should undergo screening procedures for shunt dysfunction, including invasive shunt testing.

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Tractography-based targeting of the ventral intermediate nucleus

J Neurosurg 133:1002–1009, 2020

Tractography-based targeting of the thalamic ventral intermediate nucleus (T-VIM) is a novel method conferring patient-specific selection of VIM coordinates for tremor surgery; however, its accuracy and clinical utility in magnetic resonance imaging–guided focused ultrasound (MRgFUS) thalamotomy compared to conventional indirect targeting has not been specifically addressed. This retrospective study sought to compare the treatment locations and potential adverse effect profiles of T-VIM with indirect targeting in a large cohort of MRgFUS thalamotomy patients.

METHODS T-VIM was performed using diffusion tractography outlining the pyramidal and medial lemniscus tracts in 43 MRgFUS thalamotomy patients. T-VIM coordinates were compared with the indirect treatment coordinates used in the procedure. Thalamotomy lesions were delineated on postoperative T1-weighted images and displaced (“translated”) by the anteroposterior and mediolateral difference between T-VIM and treatment coordinates. Both translated and actual lesions were normalized to standard space and subsequently overlaid with areas previously reported to be associated with an increased risk of motor and sensory adverse effects when lesioned during MRgFUS thalamotomy.

RESULTS T-VIM coordinates were 2.18 mm anterior and 1.82 mm medial to the “final” indirect treatment coordinates. Translated lesions lay more squarely within the boundaries of the VIM compared to nontranslated lesions and showed significantly less overlap with areas associated with sensory adverse effects. Translated lesions overlapped less with areas associated with motor adverse effects; however, this difference was not significant.

CONCLUSIONS T-VIM leads to the selection of more anterior and medial coordinates than the conventional indirect methods. Lesions moved toward these anteromedial coordinates avoid areas associated with an increased risk of motor and sensory adverse effects, suggesting that T-VIM may improve clinical outcomes.

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Risk factors, comorbidities, quality of life, and complications after surgery in idiopathic normal pressure hydrocephalus: review of the INPH-CRasH study

Neurosurg Focus 49 (4):E8, 2020

Idiopathic normal pressure hydrocephalus (INPH) is a dementia treatable by insertion of a shunt that drains CSF. The cause of the disease is unknown, but a vascular pathway has been suggested. The INPH-CRasH (Comorbidities and Risk Factors Associated with Hydrocephalus) study was a modern epidemiological case-control study designed to prospectively assess parameters regarding comorbidities and vascular risk factors (VRFs) for INPH, quality of life (QOL), and adverse events in patients with shunted INPH. The objective of this review was to summarize the findings of the INPH-CRasH study.

METHODS VRFs, comorbidities, QOL, and adverse events were analyzed in consecutive patients with INPH who underwent shunt placement between 2008 and 2010 in 5 of 6 neurosurgical centers in Sweden. Patients (n = 176, within the age span of 60–85 years and not having dementia) were compared to population-based age- and gender-matched controls (n = 368, same inclusion criteria as for the patients with INPH). Assessed parameters were as follows: hypertension; diabetes; obesity; hyperlipidemia; psychosocial factors (stress and depression); smoking status; alcohol intake; physical activity; dietary pattern; cerebrovascular, cardiovascular, or peripheral vascular disease; epilepsy; abdominal pain; headache; and clinical parameters before and after surgery. Parameters were assessed through questionnaires, clinical examinations, measurements, ECG studies, and blood samples.

RESULTS Four VRFs were independently associated with INPH: hyperlipidemia, diabetes, obesity, and psychosocial factors. Physical inactivity and hypertension were also associated with INPH, although not independently from the other risk factors. The population attributable risk percent for a model containing all of the VRFs associated with INPH was 24%. Depression was overrepresented in patients with INPH treated with shunts compared to the controls (46% vs 13%, p < 0.001) and the main predictor for low QOL was a coexisting depression (p < 0.001). Shunting improved QOL on a long-term basis. Epilepsy, headache, and abdominal pain remained common for a mean follow-up time of 21 months in INPH patients who received shunts.

CONCLUSIONS The results of the INPH-CRasH study are consistent with a vascular pathophysiological component of INPH. In clinical care and research, a complete risk factor analysis as well as screening for depression and a measurement for QOL should probably be included in the workup of patients with INPH. The effect of targeted interventions against modifiable VRFs and antidepressant treatment in INPH patients should be evaluated. Seizures, headache, and abdominal pain should be inquired about at postoperative follow-up examinations.

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Lower Hounsfield units on CT are associated with cage subsidence after anterior cervical discectomy and fusion

J Neurosurg Spine 33:425–432, 2020

A consequence of anterior cervical discectomy and fusion (ACDF) is graft subsidence, potentially leading to kyphosis, nonunion, foraminal stenosis, and recurrent pain. Bone density, as measured in Hounsfield units (HUs) on CT, may be associated with subsidence. The authors evaluated the association between HUs and subsidence rates after ACDF.

METHODS A retrospective study of patients treated with single-level ACDF at the University of California, San Francisco, from 2008 to 2017 was performed. HU values were measured according to previously published methods. Only patients with preoperative CT, minimum 1-year follow-up, and single-level ACDF were included. Patients with posterior surgery, tumor, infection, trauma, deformity, or osteoporosis treatment were excluded. Changes in segmental height were measured at 1-year follow-up compared with immediate postoperative radiographs. Subsidence was defined as segmental height loss of more than 2 mm.

RESULTS A total of 91 patients met inclusion criteria. There was no significant difference in age or sex between the subsidence and nonsubsidence groups. Mean HU values in the subsidence group (320.8 ± 23.9, n = 8) were significantly lower than those of the nonsubsidence group (389.1 ± 53.7, n = 83, p < 0.01, t-test). There was a negative correlation between the HU values and segmental height loss (Pearson’s coefficient −0.735, p = 0.01). Using receiver operating characteristic curves, the area under the curve was 0.89, and the most appropriate threshold of HU value was 343.7 (sensitivity 77.1%, specificity 87.5%). A preoperative lower HU is a risk factor for postoperative subsidence (binary logistic regression, p < 0.05). The subsidence rate and distance between allograft and polyetheretherketone (PEEK) materials were not significantly different (PEEK 0.9 ± 0.7 mm, allograft 1.0 ± 0.7 mm; p > 0.05).

CONCLUSIONS Lower preoperative CT HU values are associated with cage subsidence in single-level ACDF. Preoperative measurement of HUs may be useful in predicting outcomes after ACDF.

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Neurosurgical simulator for training aneurysm microsurgery

Acta Neurochirurgica (2020) 162:2313–2321

Due to its complexity and to existing treatment alternatives, exposure to intracranial aneurysm microsurgery at the time of neurosurgical residency is limited. The current state of the art includes training methods like assisting in surgeries, operating under supervision, and video training. These approaches are labor-intensive and difficult to fit into a timetable limited by the new work regulations. Existing virtual reality (VR)–based training modules lack patient-specific exercises and haptic properties and are thus inferior to hands-on training sessions and exposure to real surgical procedures.

Materials and methods We developed a physical simulator able to reproduce the experience of clipping an intracranial aneurysm based on a patient-specific 3D-printed model of the skull, brain, and arteries. The simulator is made of materials that not only imitate tissue properties including arterial wall patency, thickness, and elasticity but also able to recreate a pulsatile blood flow. A sample group of 25 neurosurgeons and residents (n = 16: early residency with less than 4 years of neurosurgical exposure; n = 9: late residency and board-certified neurosurgeons, 4–15 years of neurosurgical exposure) took part to the study. Participants evaluated the simulator and were asked to answer questions about surgical simulation anatomy, realism, haptics, tactility, and general usage, scored on a 5-point Likert scale. In order to evaluate the feasibility of a future validation study on the role of the simulator in neurosurgical postgraduate training, an expert neurosurgeon assessed participants’ clipping performance and a comparison between groups was done.

Results The proposed simulator is reliable and potentially useful for training neurosurgical residents and board-certified neurosurgeons. A large majority of participants (84%) found it a better alternative than conventional neurosurgical training methods.

Conclusion The integration of a new surgical simulator including blood circulation and pulsatility should be considered as part of the future armamentarium of postgraduate education aimed to ensure high training standards for current and future generations of neurosurgeons involved in intracranial aneurysm surgery. Resident training ,Surgical simulation,Surgical education ,Microsurgery , Intracranial aneurysm , Neurosurgery

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Role of Gamma Knife Radiosurgery in Small Cell Lung Cancer

Neurosurgery 87:664–671, 2020

Despite a high incidence of brain metastases in patients with small-cell lung cancer (SCLC), limited data exist on the use of stereotactic radiosurgery (SRS), specifically Gamma Knife™ radiosurgery (Elekta AB), for SCLC brain metastases.

OBJECTIVE: To provide a detailed analysis of SCLC patients treated with SRS, focusing on local failure, distant brain failure, and overall survival (OS). METHODS: A multi-institutional retrospective review was performed on 293 patients undergoing SRS for SCLC brain metastases at 10 medical centers from 1991 to 2017. Data collectionwas performed according to individual institutional review boards, and analyses were performed using binary logistic regression, Cox-proportional hazardmodels, Kaplan- Meier survival analysis, and competing risks analysis.

RESULTS: Two hundred thirty-two (79%) patients received SRS as salvage following prior whole-brain irradiation (WBRT) or prophylactic cranial irradiation, with a median marginal dose of 18 Gy. At median follow-up after SRS of 6.4 and 18.0 mo for surviving patients, the 1-yr local failure, distant brain failure, and OS were 31%, 49%, and 28%. The interval between WBRT and SRS was predictive of improved OS for patients receiving SRS more than 1 yr after initial treatment (21%, <1 yr vs 36%, >1 yr, P = .01). On multivariate analysis, older age was the only significant predictor for OS (hazard ratio 1.63, 95% CI 1.16-2.29, P = .005).

CONCLUSION: SRS plays an important role in the management of brain metastases from SCLC, especially in salvage therapy following WBRT. Ongoing prospective trials will better assess the value of radiosurgery in the primary management of SCLC brainmetastases and potentially challenge the standard application of WBRT in SCLC patients.

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Classification of Individual Finger Movements Using Intracortical Recordings in Human Motor Cortex

Neurosurgery, Volume 87, Issue 4, 1 October 2020, Pages 630–638

Intracortical microelectrode arrays have enabled people with tetraplegia to use a brain–computer interface for reaching and grasping. In order to restore dexterous movements, it will be necessary to control individual fingers.

OBJECTIVE: To predict which finger a participant with hand paralysis was attempting to move using intracortical data recorded from the motor cortex.

METHODS: A 31-yr-old man with a C5/6 ASIA B spinal cord injury was implanted with 2 88- channel microelectrode arrays in left motor cortex. Across 3 d, the participant observed a virtual hand flex in each finger while neural firing rates were recorded. A 6-class linear discriminant analysis (LDA) classifier, with 10 × 10-fold cross-validation, was used to predict which fingermovement was being performed (flexion/extension of all 5 digits and adduction/abduction of the thumb).

RESULTS: Themean overall classification accuracywas 67% (range: 65%-76%, chance: 17%), whichoccurredat anaverageof 560ms (range:420-780ms) aftermovementonset. Individually, thumb flexion and thumb adduction were classified with the highest accuracies at 92% and 93%, respectively. The index, middle, ring, and little achieved an accuracy of 65%, 59%, 43%, and 56%, respectively, and, when incorrectly classified, were typically marked as an adjacent finger. The classification accuracies were reflected in a low-dimensional projection of the neural data into LDA space, where the thumb-related movements were most separable from the finger movements.

CONCLUSION: Classification of intention to move individual fingers was accurately predicted by intracortical recordings from a human participant with the thumb being particularly independent.

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Cerebrospinal fluid disturbances after transcallosal surgery: incidence and predictive factors

J Neurosurg 133:979–987, 2020

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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Three-dimensional assessment of robot-assisted pedicle screw placement accuracy and instrumentation reliability based on a preplanned trajectory

J Neurosurg Spine 33:519–528, 2020

Robotic spine surgery systems are increasingly used in the US market. As this technology gains traction, however, it is necessary to identify mechanisms that assess its effectiveness and allow for its continued improvement. One such mechanism is the development of a new 3D grading system that can serve as the foundation for error-based learning in robot systems. Herein the authors attempted 1) to define a system of providing accuracy data along all three pedicle screw placement axes, that is, cephalocaudal, mediolateral, and screw long axes; and 2) to use the grading system to evaluate the mean accuracy of thoracolumbar pedicle screws placed using a single commercially available robotic system.

METHODS The authors retrospectively reviewed a prospectively maintained, IRB-approved database of patients at a single tertiary care center who had undergone instrumented fusion of the thoracic or lumbosacral spine using robotic assistance. Patients with preoperatively planned screw trajectories and postoperative CT studies were included in the final analysis. Screw accuracy was measured as the net deviation of the planned trajectory from the actual screw trajectory in the mediolateral, cephalocaudal, and screw long axes.

RESULTS The authors identified 47 patients, 51% male, whose pedicles had been instrumented with a total of 254 screws (63 thoracic, 191 lumbosacral). The patients had a mean age of 61.1 years and a mean BMI of 30.0 kg/m2. The mean screw tip accuracies were 1.3 ± 1.3 mm, 1.2 ± 1.1 mm, and 2.6 ± 2.2 mm in the mediolateral, cephalocaudal, and screw long axes, respectively, for a net linear deviation of 3.6 ± 2.3 mm and net angular deviation of 3.6° ± 2.8°. According to the Gertzbein-Robbins grading system, 184 screws (72%) were classified as grade A and 70 screws (28%) as grade B. Placement of 100% of the screws was clinically acceptable.

CONCLUSIONS The accuracy of the discussed robotic spine system is similar to that described for other surgical systems. Additionally, the authors outline a new method of grading screw placement accuracy that measures deviation in all three relevant axes. This grading system could provide the error signal necessary for unsupervised machine learning by robotic systems, which would in turn support continued improvement in instrumentation placement accuracy.

 

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Trapped fourth ventricle—treatment options and the role of open posterior fenestration in the surgical management

Acta Neurochirurgica (2020) 162:2441–2449

Trapped fourth ventricle (TFV) is a rare and difficult to treat condition. Most patients have a past inciting event (infection, IVH, trauma) and history of prior CSF diversion. The symptoms are due to the mass effect on brainstem and cerebellum. Rarely, TFV can also be associated with syrinx formation due to a dissociated craniospinal CSF flow near the fourth ventricle outlets.We present our experience and outcomes of open posterior fenestration in 11 cases, along with an overview of the surgical management of TFV.

Methods Between 2011 and 2018, 11 patients of TFV were operated by the posterior approach fenestration of the fourth ventricle outlets and arachnoid dissection. The clinical and radiological findings of the patients were retrieved from the hospital database. The surgical technique is described in detail. The patients’ neurological status and imaging findings in the follow-up were recorded and compared.

Results The average age of the patients was 23.55 years. The most common presenting symptoms were headache (9/11) and gait imbalance (7), with TB meningitis being the commonest etiology. Ten patients had a history of prior CSF diversion with two presenting with shunt malfunction. Mean follow-up duration was 33.33 months. The improvement in neurological status was observed in 9/11 patients, 2 remained status quo. On follow-up imaging, 8/11 (72.72%) patients had a decrease in the size of TFV while syrinx improved in 3/5 (60%).

Conclusion Multiple surgical approaches have been described for TFV. Endoscopic fourth ventriculostomy with aqueductoplasty is gaining popularity in the past two decades. However, an open posterior fenestration of the midline fourth ventricle outlet (magendieplasty) along with sharp arachnoid dissection (adhesiolysis) along the cerebello-medullary cisterns and paracervical gutters is relatively simple and provides physiological fourth ventricular CSF outflow. This is especially useful in TFV with syrinx as the craniospinal CSF circulation is established.

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Sphenoorbital meningioma: a unique skull base tumor. Surgical technique and results

J Neurosurg 133:1044–1051, 2020

Sphenoorbital meningioma (SOM) is a unique skull base tumor, characterized by infiltrative involvement and hyperostosis primarily of the lesser wing of sphenoid bone, with frequent involvement of the orbital compartment. SOM often manifests with proptosis and visual impairment. Surgical technique and outcome are highly variable among studies reported in the literature. The authors present a single-surgeon experience with SOM.

METHODS A retrospective review of a prospectively maintained institutional database was performed. A blinded imaging review by 2 study team members was completed to confirm SOM, after which chart review was carried out to capture demographics and outcomes. All statistical testing was completed using JMP Pro version 14.1.0, with significance defined as p < 0.05.

RESULTS Forty-seven patients who underwent surgery between 2000 and 2017 were included. The median age at surgery was 47 years (range 36–70 years), 81% of patients were female, and the median follow-up was 43 months (range 0–175 months). All operations were performed via a frontotemporal craniotomy, orbitooptic osteotomy, and anterior clinoidectomy, with extensive resection of all involved bone and soft tissue. Preoperatively, proptosis was noted in 44 patients, 98% of whom improved. Twenty-eight patients (60%) had visual deficits before surgery, 21 (75%) of whom improved during follow-up. Visual field defect other than a central scotoma was the only prognostic factor for improvement in vision on multivariate analysis (p = 0.0062). Nine patients (19%) had recurrence or progression during follow-up.

CONCLUSIONS SOM is a unique skull base tumor that needs careful planning to optimize outcome. Aggressive removal of involved bone and periorbita is crucial, and proptosis and visual field defect other than a central scotoma can improve after surgery.

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The Effect of Older Age on the Perioperative Outcomes of Spinal Fusion Surgery in Patients With Lumbar Degenerative Disc DiseaseWith Spondylolisthesis

Neurosurgery, Volume 87, Issue 4, 1 October 2020, Pages 672–678

Degenerative spondylolisthesis (DS) is often treated with lumbar spinal fusion (LSF). However, there is concern that the morbidity of LSF may be prohibitively high in older adults.

OBJECTIVE: To evaluate the impact of advanced age on the safety of LSF for DS.

METHODS: Patients who underwent LSF for DS were retrospectively identified from National Surgical Quality Improvement Program datasets for 2011 to 2015 using Current Procedural Terminology codes. Data on demographic characteristics, comorbidities, surgical factors, and 30-d morbidity and mortality were collected. Propensity score matching (nearest neighbor) was performed with age (<70 vs ≥70 yr) as the dependent variable and sex, type of fusion procedure, number of levels fused, diabetes, smoking, hypertension, and chronic steroid use as covariates. Outcomes were compared between age <70 and ≥70 groups.

RESULTS: The study cohort consisted of 2238 patients (n=1119, age<70; n=1119, age≥70). The 2 age groups were balanced for key covariates including sex, race, diabetes, hypertension, CHF, smoking, chronic steroid use, type of fusion, and number of levels. Rates of all complications were similar between younger and older age groups, except urinary tract infection, which was more frequent among the ≥70 age group (OR 2.32, P = .009). Further, patients in the older age group were more likely to be discharged to a rehabilitation (OR 2.94, P < .001) or skilled care (OR 3.66, P < .001) facility, rather than directly home (OR 0.25, P < .001).

CONCLUSION: LSF may be performed safely in older adults with DS. Our results suggest older age alone should not exclude a patient from undergoing lumbar fusion for DS.

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Predictors of Complications, Functional Outcome, and Morbidity in a Large Cohort TreatedWith Flow Diversion

Neurosurgery DOI:10.1093/neuros/nyz508

A dramatic improvement in obliteration rates of large, wide-necked aneurysms has been observed after the FDA approved the Pipeline Embolization Device (PED) in 2011.

OBJECTIVE: To assess the predictors of complications, morbidity, and unfavorable outcomes in a large cohort of patients with aneurysms treated with PED.

METHODS: A retrospective chart review of a prospectively maintained database for subjects treated with flow diversion from 2010 to 2019.

RESULTS: A total of 598 aneurysms were treated during a period extending from 2010 to 2019 (84.28% females, mean age 55.5 yr, average aneurysm size 8.49 mm). Morbidity occurred at a rate of 5.8% and mortality at a rate of 2.2%. Ischemic stroke occurred at a rate of 3%, delayed aneurysmal rupture (DAR) at 1.2%, and distal intraparenchymal hemorrhage (DIPH) at 1.5%. On multivariate analysis, the predictor of stroke was aneurysm size>15 mm. Predictors of DAR were previous subarachnoid hemorrhage (SAH), increasing aneurysm size, and posterior circulation aneurysm. Predictors of DIPH were using more than 1 PED and baseline P2Y12 value. Predictors of in-stent stenosis were the increasing year of treatment and balloon angioplasty, whereas increasing age and previous treatment were negatively associated with in-stent stenosis. Predictors of morbidity were posterior circulation aneurysms, increasing aneurysm size, and hypertension, and incidental aneurysm diagnosis was protective for morbidity.

CONCLUSION: Flow diversion is a safe and effective treatment option for aneurysms. A better understanding of predictive factors of complications, morbidity, and functional outcomes is of high importance for a more accurate risk assessment.

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Neural and vascular architecture of the septum pellucidum: an anatomical study and considerations for safe endoscopic septum pellucidotomy

J Neurosurg 133:902–911, 2020

The septum pellucidum is a bilateral thin membranous structure representing the border between the frontal horns of the lateral ventricles. Its most examined components are the septal veins due to their surgical importance during endoscopic septum pellucidotomy (ESP), which is a well-accepted method for surgical treatment of unilateral hydrocephalus. It is widely accepted that the septum pellucidum contains nerve fibers as well, but interestingly, no anatomical study has been addressed to its neural components before. The aim of the present study was to identify these elements as well as their relations to the septal veins and to define major landmarks within the ventricular system for neurosurgical use.

METHODS Nine formalin-fixed human cadaveric brains (18 septa pellucida) were involved in this study. A central block containing both septa pellucida was removed and frozen at -30°C for 2 weeks in 7 cases. The fibers of the septum pellucidum and the adjacent areas including the venous elements were dissected under magnification by using homemade wooden spatulas and microsurgical instruments. In 2 cases a histological technique was used to validate the findings of the dissections. The blocks were sliced, embedded in paraffin, cut in 7-μm-thick slices, and then stained as follows: 1) with H & E, 2) with Luxol fast blue combined with cresyl violet, and 3) with Luxol fast blue combined with Sirius red.

RESULTS The septum pellucidum and the subjacent septum verum form the medial wall of the frontal horn of the lateral ventricle. Both structures contain nerve fibers that were organized in 3 groups: 1) the precommissural fibers of the fornix; 2) the inferior fascicle; and 3) the superior fascicle of the septum pellucidum. The area directly rostral to the postcommissural column of the fornix consisted of macroscopically identifiable gray matter corresponding to the septal nuclei. The histological examinations validated the findings of the authors’ fiber dissections.

CONCLUSIONS The nerve elements of the septum pellucidum as well as the subjacent septum verum were identified with fiber dissection and verified with histology for the first time. The septal nuclei located just anterior to the fornix and the precommissural fibers of the fornix should be preserved during ESP. Considering the venous anatomy as well as the neural architecture of the septum pellucidum, the fenestration should ideally be placed above the superior edge of the fornix and preferably dorsal to the interventricular foramen.

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Volumetric analysis of bilateral spinal canal decompression via hemilaminectomy versus laminoplasty in cervical spondylotic myelopathy

Acta Neurochirurgica (2020) 162:2069–2074

Cervical spondylotic myelopathy (CSM) is a degenerative process of the cervical spine requiring surgical decompression to prevent neurological deterioration. While both anterior and posterior approaches yield satisfactory results, posterior decompression is preferred in cases of the multilevel disease. In 2015, we described a muscle-sparing, novel technique of bilateral osteoligamentous decompression via hemilaminectomy (OLD) for CSM. In this study, we investigate whether this technique offers comparable volumetric results to laminoplasty in terms of spinal canal enlargement and whether this technique can yield significant clinical improvement.

Methods Patients undergoing OLD due to CSM were prospectively enrolled in this study and then matched to and compared with a historic cohort of patients with CSM treated by laminoplasty. An independent sample t test was performed to analyze whether the volumetric gain in the two separate groups was statistically significant. Patients in the OLD cohort were clinically evaluated with the mJOA score preoperatively and 3 months postoperatively. To assess clinical improvement, a paired sample t test was performed.

Results A total of 38 patients were included in the analysis: 19 underwent OLD and 19 underwent laminoplasty. Both groups were well matched in terms of sex, age, preoperative spinal canal volume, and involved levels. Both surgical methods yielded statistically significant volumetric gain in the cervical spinal canal, but a trend towards a greater volume gain was seen in the OLD group. In the OLD group, a statistically significant clinical improvement was also demonstrated.

Conclusions Our study reveals that OLD can yield a comparable extent of decompression to laminoplasty in CSM while also delivering statistically significant clinical improvement.

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The membrane of Liliequist—a safe haven in the middle of the brain.

Acta Neurochirurgica (2020) 162:2235–2244

The membrane of Liliequist is one of the best-known inner arachnoid membranes and an essential intraoperative landmark when approaching the interpeduncular cistern but also an obstacle in the growth of lesions in the sellar and parasellar regions. The limits and exact anatomical description of this membrane are still unclear, as it blends into surrounding structures and joins other arachnoid membranes.

Methods We performed a systematic narrative review by searching for articles describing the anatomy and the relationship of the membrane of Liliequist with surrounding structures in MEDLINE, Embase and Google Scholar. Included articles were crosschecked for missing references. Both preclinical and clinical studies were included, if they detailed the clinical relevance of the membrane of Liliequist.

Results Despite a common definition of the localisation of the membrane of Liliequist, important differences exist with respect to its anatomical borders. The membrane appears to be continuous with the pontomesencephalic and pontomedullary membranes, leading to an arachnoid membrane complex around the brainstem. Furthermore, Liliequist’s membrane most likely continues along the oculomotor nerve sheath in the cavernous sinus, blending into and giving rise to the carotid-oculomotor membrane.

Conclusion Further standardized anatomical studies are needed to clarify the relation of the membrane of Liliequist with surrounding structures but also the anatomy of the arachnoid membranes in general. Our study supports this endeavour by identifying the knowledge hiatuses and reviewing the current knowledge base.

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