Morphological changes of the dorsal contour of the corpus callosum during the first two years of life.

BACKGROUND: In the medicolegal literature, focal concavities or notching of the corpus callosum has been thought to be associated with fetal alcohol spectrum disorders. Recent work suggests corpus callosum notching is a dynamic and normal anatomical feature, although it has not yet been defined in early life or infancy. OBJECTIVE: Our purpose was to characterize the dorsal contour of the corpus callosum during the first 2 years of life by defining the prevalence, onset and trajectory of notching on midsagittal T1-weighted images. MATERIALS AND METHODS: We reviewed retrospectively 1,157 consecutive patients between birth and 2 years of age. Corpus callosum morphology was evaluated and described. A notch was defined as a dorsal concavity of at least 1 mm in depth along the dorsal surface of the corpus callosum. Patient age as well as notch depth, location, number and presence of the pericallosal artery in the notch were noted. RESULTS: Two hundred thirty-three notches were identified in 549 patients: 36 anterior, 194 posterior and 3 patients with undulations. A statistically significant (R2=0.53, Beta=0.021, P=0.002) positive correlation between posterior notch prevalence and age in months was noted. A positive correlation between age and depth of the posterior notch was also statistically significant (r=0.32, n=179, P≤0.001). A trend for increased anterior notch prevalence with age was identified with significant correlation between visualized pericallosal artery indentation and anterior notching (r=0.20, n=138, P=0.016). Sub-analysis of the first month of life showed corpus callosum notching was not present. CONCLUSION: The presence of posterior notching increased significantly with age and was more frequent than that of anterior notching. Corpus callosum notching was absent in the first week of life, building on prior studies suggesting corpus callosum notching is acquired. This study provides baseline data on normative corpus callosum notching trajectories by age group during early life, a helpful correlate when associating corpus callosum morphology with disease.

Innovative growth and development of a neurological surgery residency cadaveric spine-simulation training program: a single-institution experience.

OBJECTIVE: Cadaveric and dry 3D model-based simulation training is a valuable educational tool for neurosurgical residents. Such simulation training is an opportunity for residents to hone technical skills and decision-making and enhance their neuroanatomy knowledge. The authors describe the growth and development of the Oregon Health & Science University Department of Neurological Surgery resident-focused, hands-on, spine-simulation surgery courses and provide details of course evaluations, layout, and setup. METHODS: A four-part spine surgical simulation series, including two human cadaveric and two dry 3D model-based courses, was created to provide resident spine procedure training. Residents participated in the spine simulation series (2017-2021) and completed annual course curriculum and anonymous post-course evaluations. Evaluations included both Likert scale items and free-text responses. Responses to Likert scale items were analyzed in Python. Free-text responses were quantified using the Valence Aware Dictionary for Sentiment Reasoner. Descriptive statistics were calculated and plotted using Python's seaborn and matplotlib library modules. RESULTS: The analysis included 129 spine (occipitocervical, thoracolumbar, and spine model fusion I and II) simulation course evaluations. Likert responses demonstrated high average responses for evaluation questions (4.67 ± 0.90 and above). The average compound sentiment value was 0.58 ± 0.28. CONCLUSIONS: This is the first time Likert responses and sentiment analysis have been used to demonstrate how neurosurgical residents positively value a hands-on spine simulation training. Simulation is an essential component of neurosurgical resident education training. The authors encourage other neurosurgical education programs to develop and leverage spine simulation as a teaching tool.

Innovative growth and development of a neurological surgery residency cadaveric skull base simulation training program: A single institution experience.

OBJECTIVE: Neurosurgical cadaveric and simulation training is a valuable opportunity for residents and fellows to develop as neurosurgeons, further neuroanatomy knowledge, and develop decision-making and technical expertise. The authors describe the growth and development of Oregon Health & Science University (OHSU) Department of Neurological Surgery (NSG) resident hands-on simulation skull base course and provide details of course layout and setup. METHODS: A three-part surgical simulation series was created to provide training in cadaveric skull base procedures. Course objectives were outlined for participants. Residents participated in NSG hands-on simulation courses (years 2015-2020) and completed annual course curriculum and anonymous course evaluations, which included free text reviews. Courses were evaluated by Likert scale analysis within Python, and free text was quantified using Valence Aware Dictionary for sEntiment Reasoning (VADER). Descriptive statistics were calculated and plotted using Python's Seaborn and Matplotlib library modules. RESULTS: Analysis included 162 skull base (anterior fossa, middle fossa and lateral, and endoscopic endonasal-based) simulation course evaluations. Resident responses were overwhelmingly positive. Likert responses demonstrated high average responses for each question (4.62 ± 0.56 and above). A positive attitude about simulation courses is supported by an average compound sentiment value of 0.558 ± 0.285. CONCLUSION: This is the first time Likert responses and sentiment analysis have been used to demonstrate how neurosurgical residents view a comprehensive, multi-year hands-on simulation training program. We hope the information presented serves as a guide for other institutions to develop their own residency educational curriculum in cadaveric skull base procedures.

TxBR montage reconstruction for large field electron tomography.

Electron tomography (ET) has been proven an essential technique for imaging the structure of cells beyond the range of the light microscope down to the molecular level. Large-field high-resolution views of biological specimens span more than four orders of magnitude in spatial scale, and, as a consequence, are rather difficult to generate directly. Various techniques have been developed towards generating those views, from increasing the sensor array size to implementing serial sectioning and montaging. Datasets and reconstructions obtained by the latter techniques generate multiple three-dimensional (3D) reconstructions, that need to be combined together to provide all the multiscale information. In this work, we show how to implement montages within TxBR, a tomographic reconstruction software package. This work involves some new application of mathematical concepts related to volume preserving transformations and issues of gauge ambiguity, which are essential problems arising from the nature of the observation in an electron microscope. The purpose of TxBR is to handle those issues as generally as possible in order to correct for most distortions in the 3D reconstructions and allow for a seamless recombination of ET montages.

Combined magnetic field results in higher fusion rates than pulsed electromagnetic field bone stimulation after thoracolumbar fusion surgery.

BACKGROUND: Bone growth stimulators have been used as an adjunct to spinal fusion surgery in efforts to increase fusion rates. METHODS: The authors retrospectively reviewed the medical records of patients who underwent thoracolumbar fusion surgeries by a single surgeon. Patients were then separated into three groups; pulsed electromagnetic field stimulation (PEMF), combined magnetic field stimulation (CMF) or no stimulation (NS), and computed tomography radiographic results at least 1 year after surgery were compared (solid fusion, stable nonunion, and pseudarthrosis). RESULTS: A total of 60 patients were included; 16 (26.7%) used PEMF, 24 (40.0%) used CMF, and 20 (33.3%) had NS. There were no significant differences in patient demographics. There was no difference in the mean fusion levels (p = 0. 477). Solid fusion was achieved in 11/16 (68.8%) PEMF, 21/24 (87.5%) CMF, and 20/20 (100.0%) NS patients. Stable nonunion was displayed in 2/24 (8.3%) CMF, and zero PEMF and NS patients. There were 5/16 (31.3%) PEMF, 1/24 (4.2%) CMF, and zero NS patients demonstrating radiologic pseudarthrosis. There was a statistically significant difference between PEMF and CMF (p = 0.017) and between PEMF and NS (p = 0.006) groups. No statistical difference was found between CMF and NS (p = 1.000). CONCLUSION: This is the first study to compare PEMF and CMF bone growth stimulators in patients with degenerative pathologies who underwent thoracolumbar spinal fusions. Overall, the addition of these bone growth stimulators does not improve fusion outcomes, although CMF appears superior to PEMF.

Intraoperative neuromonitoring for one-level lumbar discectomies is low yield and cost-ineffective.

BACKGROUND: Intraoperative neuromonitoring is a common, well-established modality used in spine surgery to prevent intraoperative neural injury. Neuromonitoring use in lumbar discectomy, however, is based on surgeon preference, without evidence-based data. The purpose of this research was to determine intraoperative utility and overall cost effectiveness of neuromonitoring for lumbar discectomy. METHODS: We retrospectively reviewed adult patients who underwent a lumbar discectomy, with at least 1 month of follow-up at a single tertiary care center. Patient age, sex, body mass index (BMI), lumbar level operated, and operative time and cost were collected. Neuromonitoring and operative reports were reviewed for any electromyography (EMG) abnormalities noted intraoperatively, pre- and post-operative motor exam and post-operative pain relief were collected. RESULTS: Ninety-one (47 with and 44 without neuromonitoring) lumbar discectomy cases were reviewed. There was no significant difference between mean age, sex, and BMI between the two groups. There was a significant (p = 0.006) increase in operating room time (174 min; with vs. 144 min; without neuromonitoring). Neuromonitoring was associated with a significant (p = 0.006) overall operative cost ($21,949; with vs. $18,064; without). Of the 47 cases with neuromonitoring; one had abnormal intraoperative EMG activity, which returned to normal by case conclusion. No patient in either group demonstrated new post-operative motor weakness. There was no difference in the number of patients who endorsed post-operative pain relief between the two groups. CONCLUSIONS: Neuromonitoring for lumbar discectomy confers greater operative time and cost, without any difference in neurological outcome.

PEEK interbody devices for multilevel anterior cervical discectomy and fusion: association with more than 6-fold higher rates of pseudarthrosis compared to structural allograft.

OBJECTIVE: Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucent properties and a modulus of elasticity similar to that of bone. PEEK devices also result in higher billing costs than allograft, which may drive selection. A previous study found a 5-fold higher rate of pseudarthrosis with the use of PEEK devices compared with structural allograft in single-level ACDF. Here the authors report on the occurrence of pseudarthrosis with PEEK devices versus structural allograft in patients who underwent multilevel ACDF. METHODS: The authors retrospectively reviewed 81 consecutive patients who underwent a multilevel ACDF and had radiographic follow-up for at least 1 year. Data were collected on age, sex, BMI, tobacco use, pseudarthrosis, and rate of reoperation for pseudarthrosis. Logistic regression was used for data analysis. RESULTS: Of 81 patients, 35 had PEEK implants and 46 had structural allograft. There were no significant differences between age, sex, smoking status, or BMI in the 2 groups. There were 26/35 (74%) patients with PEEK implants who demonstrated radiographic evidence of pseudarthrosis, compared with 5/46 (11%) patients with structural allograft (p < 0.001, OR 22.2). Five patients (14%) with PEEK implants required reoperation for pseudarthrosis, compared with 0 patients with allograft (p = 0.013). CONCLUSIONS: This study reinforces previous findings on 1-level ACDF outcomes and suggests that the use of PEEK in multilevel ACDF results in statistically significantly higher rates of radiographic pseudarthrosis and need for revision surgery than allograft. Surgeons should consider these findings when determining graft options, and reimbursement policies should reflect these discrepancies.

Anterior Cervical Arthrodesis With Polyetheretherketone Spacers: What is the Role of the Grafting Material?

STUDY DESIGN: This was a retrospective study of 2 surgeons' use of a single polyetheretherketone (PEEK) device. OBJECTIVE: Our objective was to investigate the fusion adjunct placed within PEEK devices to examine the likelihood of an arthrodesis, regardless of the PEEK interbody device itself. SUMMARY OF BACKGROUND DATA: The effectiveness of PEEK interbody devices in anterior cervical arthrodesis has been questioned. METHODS: The authors retrospectively reviewed the results of 121 patients with demineralized bone matrix (DBM) and 96 with local autograft bone placed within identical PEEK devices for anterior cervical arthrodesis (from 2011 to 2018); 1 surgeon used DBM and another local autograft bone. Arthrodesis was determined independently by a surgeon and 2 blinded neuroradiologists. RESULTS: For DBM versus autograft; mean age was 60 versus 61 years, smoking status 42.1% versus 31%, diabetes mellitus 18.2% versus 28%, mean body mass index 31 versus 30, and follow up averaged 17 months in both groups. For DBM versus autograft; a radiographic arthrodesis was observed in 22.3% versus 76% of patients. Refusion at the index level was required in 5.8% of the DBM and 0% of the autograft patients. CONCLUSIONS: A PEEK interbody device filled with local autograft resulted in a higher radiographic fusion rate and a lower need for reoperation at the index level than an identical device filled with DBM. Caution is warranted in assigning fusion failure to the PEEK device alone in anterior cervical discectomy and fusion surgery.

Natural history of neuromodulation devices and therapies: a patient-centered survival analysis.

OBJECTIVE: Despite rapid development and expansion of neuromodulation technologies, knowledge about device and/or therapy durability remains limited. The aim of this study was to evaluate the long-term rate of hardware and therapeutic failure of implanted devices for several neuromodulation therapies. METHODS: The authors performed a retrospective analysis of patients' device and therapy survival data (Kaplan-Meier survival analysis) for deep brain stimulation (DBS), vagus nerve stimulation (VNS), and spinal cord stimulation (SCS) at a single institution (years 1994-2015). RESULTS: During the study period, 450 patients underwent DBS, 383 VNS, and 128 SCS. For DBS, the 5- and 10-year initial device survival was 87% and 73%, respectively, and therapy survival was 96% and 91%, respectively. For VNS, the 5- and 10-year initial device survival was 90% and 70%, respectively, and therapy survival was 99% and 97%, respectively. For SCS, the 5- and 10-year initial device survival was 50% and 34%, respectively, and therapy survival was 74% and 56%, respectively. The average initial device survival for DBS, VNS, and SCS was 14 years, 14 years, and 8 years while mean therapy survival was 18 years, 18 years, and 12.5 years, respectively. CONCLUSIONS: The authors report, for the first time, comparative device and therapy survival rates out to 15 years for large cohorts of DBS, VNS, and SCS patients. Their results demonstrate higher device and therapy survival rates for DBS and VNS than for SCS. Hardware failures were more common among SCS patients, which may have played a role in the discontinuation of therapy. Higher therapy survival than device survival across all modalities indicates continued therapeutic benefit beyond initial device failures, which is important to emphasize when counseling patients.

Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion.

In BriefThe authors examined fusion rates after single-level anterior cervical discectomy and fusion, comparing use of a structural allograft with use of polyetheretherketone (PEEK) interbody devices packed with bone graft. The results demonstrate superior results of structural allograft in terms of arthrodesis rates and reoperation rates. Currently, reimbursement rates substantially favor the use of PEEK and other synthetic devices, which the authors believe should be changed based on the results of this study.

Longitudinal relaxographic imaging of white matter hyperintensities in the elderly.

BACKGROUND: Incidental white matter hyperintensities (WMHs) are common findings on T2-weighted magnetic resonance images of the aged brain and have been associated with cognitive decline. While a variety of pathogenic mechanisms have been proposed, the origin of WMHs and the extent to which lesions in the deep and periventricular white matter reflect distinct etiologies remains unclear. Our aim was to quantify the fractional blood volume (vb) of small WMHs in vivo using a novel magnetic resonance imaging (MRI) approach and examine the contribution of blood-brain barrier disturbances to WMH formation in the deep and periventricular white matter. METHODS: Twenty-three elderly volunteers (aged 59-82 years) underwent 7 Tesla relaxographic imaging and fluid-attenuated inversion recovery (FLAIR) MRI. Maps of longitudinal relaxation rate constant (R1) were prepared before contrast reagent (CR) injection and throughout CR washout. Voxelwise estimates of vb were determined by fitting temporal changes in R1 values to a two-site model that incorporates the effects of transendothelial water exchange. Average vb values in deep and periventricular WMHs were determined after semi-automated segmentation of FLAIR images. Ventricular permeability was estimated from the change in CSF R1 values during CR washout. RESULTS: In the absence of CR, the total water fraction in both deep and periventricular WMHs was increased compared to normal appearing white matter (NAWM). The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g). In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability. CONCLUSIONS: Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact. These findings support varying contributions of blood-brain barrier and brain-CSF interface disturbances in the pathophysiology of deep and periventricular WMHs in the aged human brain.

Structure-function studies of blood and air capillaries in chicken lung using 3D electron microscopy.

Avian pulmonary capillaries differ from those of mammals in three important ways. The blood-gas barrier is much thinner, it is more uniform in thickness, and the capillaries are far more rigid when their transmural pressure is altered. The thinness of the barrier is surprising because it predisposes the capillaries to stress failure. A possible mechanism for these differences is that avian pulmonary capillaries, unlike mammalian, are supported from the outside by air capillaries, but the details of the support are poorly understood. To clarify this we studied the blood and air capillaries in chicken lung using transmission electron microscopy (EM) and two relatively new techniques that allow 3D visualization: electron tomography and serial block-face scanning EM. These studies show that the pulmonary capillaries are flanked by epithelial bridges composed of two extremely thin epithelial cells with large surface areas. The junctions of the bridges with the capillary walls show thickening of the epithelial cells and an accumulation of extracellular matrix. Collapse of the pulmonary capillaries when the pressure outside them is increased is apparently prevented by the guy wire-like action of the epithelial bridges. The enlarged junctions between the bridges and the walls could provide a mechanism that limits the hoop stress in the capillary walls when the pressure inside them is increased. The support of the pulmonary capillaries may also be explained by an interdependence mechanism whereby the capillaries are linked to a rigid assemblage of air capillaries. These EM studies show the supporting structures in greater detail than has previously been possible, particularly in 3D, and they allow a more complete analysis of the mechanical forces affecting avian pulmonary capillaries.