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Wuyang Yang, Jordina Rincon-Torroella, James Feghali, Adham M. Khalafallah, Wataru Ishida, Alexander Perdomo-Pantoja, Alfredo Quiñones-Hinojosa, Michael Lim, Gary L. Gallia, Gregory J. Riggins, William S. Anderson, Sheng-Fu Larry Lo, Daniele Rigamonti, Rafael J. Tamargo, Timothy F. Witham, Ali Bydon, Alan R. Cohen, George I. Jallo, Alban Latremoliere, Mark G. Luciano, Debraj Mukherjee, Alessandro Olivi, Lintao Qu, Ziya L. Gokaslan, Daniel M. Sciubba, Betty Tyler, Henry Brem, and Judy Huang

OBJECTIVE

International research fellows have been historically involved in academic neurosurgery in the United States (US). To date, the contribution of international research fellows has been underreported. Herein, the authors aimed to quantify the academic output of international research fellows in the Department of Neurosurgery at The Johns Hopkins University School of Medicine.

METHODS

Research fellows with Doctor of Medicine (MD), Doctor of Philosophy (PhD), or MD/PhD degrees from a non-US institution who worked in the Hopkins Department of Neurosurgery for at least 6 months over the past decade (2010–2020) were included in this study. Publications produced during fellowship, number of citations, and journal impact factors (IFs) were analyzed using ANOVA. A survey was sent to collect information on personal background, demographics, and academic activities.

RESULTS

Sixty-four international research fellows were included, with 42 (65.6%) having MD degrees, 17 (26.6%) having PhD degrees, and 5 (7.8%) having MD/PhD degrees. During an average 27.9 months of fellowship, 460 publications were produced in 136 unique journals, with 8628 citations and a cumulative journal IF of 1665.73. There was no significant difference in total number of publications, first-author publications, and total citations per person among the different degree holders. Persons holding MD/PhDs had a higher number of citations per publication per person (p = 0.027), whereas those with MDs had higher total IFs per person (p = 0.048). Among the 43 (67.2%) survey responders, 34 (79.1%) had nonimmigrant visas at the start of the fellowship, 16 (37.2%) were self-paid or funded by their country of origin, and 35 (81.4%) had mentored at least one US medical student, nonmedical graduate student, or undergraduate student.

CONCLUSIONS

International research fellows at the authors’ institution have contributed significantly to academic neurosurgery. Although they have faced major challenges like maintaining nonimmigrant visas, negotiating cultural/language differences, and managing self-sustainability, their scientific productivity has been substantial. Additionally, the majority of fellows have provided reciprocal mentorship to US students.

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Camilo Molina, Daniel M. Sciubba, Christopher Chaput, P. Justin Tortolani, George I. Jallo, and Ryan M. Kretzer

Object

Translaminar screws (TLSs) were originally described as a safer alternative to pedicle and transarticular screw placement at C-2 in adult patients. More recently, TLSs have been used in both the cervical and thoracic spine of pediatric patients as a primary fixation technique and as a bailout procedure when dysplastic pedicle morphology prohibits safe pedicle screw placement. Although authors have reported the anatomical characteristics of the cervical and thoracic lamina in adults as well as those of the cervical lamina in pediatric patients, no such data exist to guide safe TLS placement in the thoracic spine of the pediatric population. The goal of this study was to report the anatomical feasibility of TLS placement in the thoracic spine of pediatric patients.

Methods

Fifty-two patients (26 males and 26 females), with an average age of 9.5 ± 4.8 years, were selected by retrospective review of a trauma registry database after institutional review board approval. Study inclusion criteria were an age from 2 to 16 years, standardized axial bone-window CT images of the thoracic spine, and the absence of spinal trauma. For each thoracic lamina the following anatomical features were measured using eFilm Lite software: laminar width (outer cortical and cancellous), laminar height (LH), maximal screw length, and optimal screw trajectory. Patients were stratified by age (an age < 8 versus ≥ 8 years) and sex.

Results

Collected data demonstrate the following general trends as one descends the thoracic spine from T-1 to T-12: 1) increasing laminar width to T-4 followed by a steady decrease to T-12, 2) increasing LH, 3) decreasing maximal screw length, and 4) increasing ideal screw trajectory angle. When stratified by age and sex, male patients older than 8 years of age had significantly larger laminae in terms of both width and height and allowed significantly longer screw placement at all thoracic levels compared with their female counterparts. Importantly, it was found that 78% of individual thoracic laminae, regardless of age or sex, could accept a 4.0-mm screw with 1.0 mm of clearance. As expected, when stratifying by age and sex, it was found that older male patients had the highest acceptance rates.

Conclusions

Data in the present study provide information regarding optimal TLS length, diameter, and trajectory for each thoracic spinal level in pediatric patients. Importantly, the data collected demonstrate no anatomical limitations within the pediatric thoracic spine to TLS instrumentation, although acceptance rates are lower for younger (< 8 years old) and/or female patients. Lastly, given the anatomical variation found in this study, CT scanning can be useful in the preoperative setting when planning TLS use in the thoracic spine of pediatric patients.

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Ryan M. Kretzer, Christopher Chaput, Daniel M. Sciubba, Ira M. Garonzik, George I. Jallo, Paul C. McAfee, Bryan W. Cunningham, and P. Justin Tortolani

Object

The objective of this study was to establish normative data for thoracic pedicle anatomy in the US adult population. To this end, CT scans chosen at random from an adult database were evaluated to determine the ideal pedicle screw (PS) length, diameter, trajectory, and starting point in the thoracic spine. The role of patient sex and side of screw placement were also assessed. The authors postulated that this information would be of value in guiding safe implant size and placement for surgeons in training.

Methods

One hundred patients (50 males and 50 females) were selected via retrospective review of a hospital trauma registry database over a 6-month period. Patients included in the study were older than 18 years of age, had axial bone-window CT images of the thoracic spine, and had no evidence of spinal trauma. For each pedicle, the pedicle width, pedicle-rib width, estimated screw length, trajectory, and ideal entry point were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test.

Results

The shortest mean estimated PS length was at T-1 (33.9 ± 3.3 mm), and the longest was at T-9 (44.9 ± 4.4 mm). Pedicle screw length was significantly affected by patient sex; men could accommodate a PS from T1–12 a mean of 4.0 ± 1.0 mm longer than in women (p < 0.001). Pedicle width showed marked variation by spinal level, with T-4 (4.4 ± 1.1 mm) having the narrowest width and T-12 (8.3 ± 1.7 mm) having the widest. Pedicle width had an obvious affect on potential screw diameter; 65% of patients had a least 1 pedicle at T-4 that was < 5 mm in diameter and therefore would not accept a 4.0-mm screw with 1.0 mm of clearance, as compared with only 2% of patients with a similar status at T-12. Sex variation was also apparent, as thoracic pedicles from T-1 to T-12 were a mean of 1.4 ± 0.2 mm wider in men than in women (p < 0.001). The PS trajectory in the axial plane was measured, showing a marked decrease from T-1 to T-4, stabilization from T-5 to T-10, followed by a decrease at T11–12. When screw trajectory was stratified by side of placement, a mean of 1.7° ± 0.5° of increased medialization was required for ideal pedicle cannulation from T-3 to T-12 on the left as compared with the right side, presumably because of developmental changes in the vertebral body caused by the aorta (p < 0.05 for T3–12, except for T-5, where p = 0.051). The junction of the superior articular process, lamina, and the superior ridge of the transverse process was shown to be a conserved surface landmark for PS placement.

Conclusions

Preoperative CT evaluation is important in choosing PS length, diameter, trajectory, and entry point due to variation based on spinal level, patient sex, and side of placement. These data are valuable for resident and fellow training to guide the safe use of thoracic PSs.

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Ryan M. Kretzer, Nianbin Hu, Hidemasa Umekoji, Daniel M. Sciubba, George I. Jallo, Paul C. McAfee, P. Justin Tortolani, and Bryan W. Cunningham

Object

Thoracic pedicle screw instrumentation is often indicated in the treatment of trauma, deformity, degenerative disease, and oncological processes. Although classic teaching for cervical spine constructs is to bridge the cervicothoracic junction (CTJ) when instrumenting in the lower cervical region, the indications for extending thoracic constructs into the cervical spine remain unclear. The goal of this study was to determine the role of ligamentous and facet capsule (FC) structures at the CTJ as they relate to stability above thoracic pedicle screw constructs.

Methods

A 6-degree-of-freedom spine simulator was used to test multidirectional range of motion (ROM) in 8 human cadaveric specimens at the C7–T1 segment. Flexion-extension, lateral bending, and axial rotation at the CTJ were tested in the intact condition, followed by T1–6 pedicle screw fixation to create a long lever arm inferior to the C7–T1 level. Multidirectional flexibility testing of the T1–6 pedicle screw construct was then sequentially performed after sectioning the C7–T1 supraspinous ligament/interspinous ligament (SSL/ISL) complex, followed by unilateral and bilateral FC disruption at C7–T1. Finally, each specimen was reconstructed using C5–T6 instrumented fixation and ROM testing at the CTJ performed as previously described.

Results

Whereas the application of a long-segment thoracic construct stopping at T-1 did not significantly increase flexion-extension peak total ROM at the supra-adjacent level, sectioning the SSL/ISL significantly increased flexibility at C7–T1, producing 35% more motion than in the intact condition (p < 0.05). Subsequent FC sectioning had little additional effect on ROM in flexion-extension. Surprisingly, the application of thoracic instrumentation had a stabilizing effect on the supra-adjacent C7–T1 segment in axial rotation, leading to a decrease in peak total ROM to 83% of the intact condition (p < 0.05). This is presumably due to interaction between the T-1 screw heads and titanium rods with the C7–T1 facet joints, thereby limiting axial rotation. Incremental destabilization served only to restore peak total ROM near the intact condition for this loading mode. In lateral bending, the application of thoracic instrumentation stopping at T-1, as well as SSL/ISL and FC disruption, demonstrated trends toward increased supraadjacent ROM; however, these trends did not reach statistical significance (p > 0.05).

Conclusions

When stopping thoracic constructs at T-1, care should be taken to preserve the SSL/ISL complex to avoid destabilization of the supra-adjacent CTJ, which may manifest clinically as proximal-junction kyphosis. In an analogous fashion, if a T-1 laminectomy is required for neural decompression or surgical access, consideration should be given to extending instrumentation into the cervical spine. Facet capsule disruption, as might be encountered during T-1 pedicle screw placement, may not be an acutely destabilizing event, due to the interaction of the C7–T1 facet joints with T-1 instrumentation.

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Ryan M. Kretzer, Christopher Chaput, Daniel M. Sciubba, Ira M. Garonzik, George I. Jallo, Paul C. McAfee, Bryan W. Cunningham, and P. Justin Tortolani

Object

Translaminar screws (TLSs) offer an alternative to pedicle screw (PS) fixation in the upper thoracic spine. Although cadaveric studies have described the anatomy of the laminae and pedicles at T1–2, CT imaging is the modality of choice for presurgical planning. In this study, the goal was to determine the diameter, maximal screw length, and optimal screw trajectory for TLS placement at T1–2, and to compare this information to PS placement in the upper thoracic spine as determined by CT evaluation.

Methods

One hundred patients (50 men and 50 women), whose average age was 41.7 ± 19.6 years, were selected by retrospective review of a trauma registry database over a 6-month period. Patients were included in the study if they were over the age of 18, had standardized axial bone-window CT imaging at T1–2, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and cancellous), maximal screw length, and optimal screw trajectory were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test.

Results

The T-1 lamina was estimated to accommodate, on average, a 5.8-mm longer screw than the T-2 lamina (p < 0.001). At T-1, the maximal TLS length was similar to PS length (TLS: 33.4 ± 3.6 mm, PS: 33.9 ± 3.3 mm [p = 0.148]), whereas at T-2, the maximal PS length was significantly greater than the TLS length (TLS: 27.6 ± 3.1 mm, PS: 35.3 ± 3.5 mm [p < 0.001]). When the lamina outer cortical and cancellous width was compared between T-1 and T-2, the lamina at T-2 was, on average, 0.3 mm wider than at T-1 (p = 0.007 and p = 0.003, respectively). In comparison with the corresponding pedicle, the mean outer cortical pedicle width at T-1 was wider than the lamina by an average of 1.0 mm (lamina: 6.6 ± 1.1 mm, pedicle: 7.6 ± 1.3 mm [p < 0.001]). At T-2, however, outer cortical lamina width was wider than the corresponding pedicle by an average of 0.6 mm (lamina: 6.9 ± 1.1 mm, pedicle: 6.3 ± 1.2 mm [p < 0.001]). At T-1, 97.5% of laminae measured could accept a 4.0-mm screw with 1.0 mm of clearance, compared with 99.5% of T-1 pedicles; whereas at T-2, 99% of laminae met this requirement, compared with 94.5% of pedicles. The ideal screw trajectory was also measured (T-1: 49.2 ± 3.7° for TLS and 32.8 ± 3.8° for PS; T-2: 51.1 ± 3.5° for TLS and 20.5 ± 4.4° for PS).

Conclusions

Based on CT evaluation, there are no anatomical limitations to the placement of TLSs compared with PSs at T1–2. Differences were noted, however, in lamina length and width between T-1 and T-2 that must be considered when placing TLS at these levels.

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Giannina L. Garcés-Ambrossi, Matthew J. McGirt, Vivek A. Mehta, Daniel M. Sciubba, Timothy F. Witham, Ali Bydon, Jean-Paul Wolinksy, George I. Jallo, and Ziya L. Gokaslan

Object

With the introduction of electrophysiological spinal cord monitoring, surgeons have been able to perform radical resection of intramedullary spinal cord tumors (IMSCTs). However, factors associated with tumor resectability, tumor recurrence, and long-term neurological outcome are poorly understood.

Methods

The authors retrospectively reviewed 101 consecutive cases of IMSCT resection in adults and children at a single institution. Neurological function and MR images were evaluated preoperatively, at discharge, 1 month after surgery, and every 6 months thereafter. Factors associated with gross-total resection (GTR), progression-free survival (PFS), and long-term neurological improvement were assessed using multivariate regression analysis.

Results

The mean age of the patients was 41 ± 18 years and 17 (17%) of the patients were pediatric. Pathological type included ependymoma in 51 cases, hemangioblastoma in 15, pilocytic astrocytoma in 16, WHO Grade II astrocytoma in 10, and malignant astrocytoma in 9. A GTR was achieved in 60 cases (59%). Independent of histological tumor type, an intraoperatively identifiable tumor plane (OR 25.3, p < 0.0001) and decreasing tumor size (OR 1.2, p = 0.05) were associated with GTR. Thirty-four patients (34%) experienced acute neurological decline after surgery (associated with increasing age [OR 1.04, p = 0.02] and with intraoperative change in motor evoked potentials [OR 7.4, p = 0.003]); in 14 (41%) of these patients the change returned to preoperative baseline within 1 month. In 31 patients (31%) tumor progression developed by last follow-up (mean 19 months). Tumor histology (p < 0.0001) and the presence of an intraoperatively identified tumor plane (hazard ratio [HR] 0.44, p = 0.027) correlated with improved PFS. A GTR resulted in improved PFS for hemangioblastoma (HR 0.004, p = 0.04) and ependymoma (HR 0.2, p = 0.02), but not astrocytoma. Fifty-five patients (55%) maintained overall neurological improvement by last follow-up. The presence of an identifiable tumor plane (HR 3.1, p = 0.0004) and improvement in neurological symptoms before discharge (HR 2.3, p = 0.004) were associated with overall neurological improvement by last follow-up (mean 19 months).

Conclusions

Gross-total resection can be safely achieved in the vast majority of IMSCTs when an intraoperative plane is identified, independent of pathological type. The incidence of acute perioperative neurological decline increases with patient age but will improve to baseline in nearly half of patients within 1 month. Long-term improvement in motor, sensory, and bladder dysfunction may be achieved in a slight majority of patients and occurs more frequently in patients in whom a surgical plane can be identified. A GTR should be attempted for ependymoma and hemangioblastoma, but it may not affect PFS for astrocytoma. For all tumors, the intraoperative finding of a clear tumor plane of resection carries positive prognostic significance across all pathological types.

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Giannina L. Garcés-Ambrossi, Matthew J. McGirt, Roger Samuels, Daniel M. Sciubba, Ali Bydon, Ziya L. Gokaslan, and George I. Jallo

Object

Although postsurgical neurological outcomes in patients with tethered cord syndrome (TCS) are well known, the rate and development of neurological improvement after first-time tethered cord release is incompletely understood. The authors reviewed their institutional experience with the surgical management of adult TCS to assess the time course of symptomatic improvement, and to identify the patient subgroups most likely to experience improvement of motor symptoms.

Methods

The authors retrospectively reviewed 29 consecutive cases of first-time adult tethered cord release. Clinical symptoms of pain and motor and urinary dysfunction were evaluated at 1 and 3 months after surgery, and then every 6 months thereafter. Rates of improvement in pain and motor or urinary dysfunction over time were identified, and presenting factors associated with improvement of motor symptoms were assessed using a multivariate survival analysis (Cox model).

Results

The mean patient age was 38 ± 13 years. The causes of TCS included lipomyelomeningocele in 3 patients (10%), tight filum in 3 (10%), lumbosacral lipoma in 4 (14%), intradural tumor in 3 (10%), previous lumbosacral surgery in 2 (7%), and previous repair of myelomeningocele in 14 (48%). The mean ± SD duration of symptoms before presentation was 5 ± 7 months. Clinical presentation included diffuse pain/parasthesias in both lower extremities in 13 patients (45%), or perineal distribution in 18 (62%), lower extremity weakness in 17 (59%), gait difficulties in 17 (59%), and bladder dysfunction in 14 (48%). Laminectomy was performed in a mean of 2.5 ± 0.7 levels per patient, and 9 patients (30%) received duraplasty. At 18 months postoperatively, 47% of patients had improved urinary symptoms, 69% had improved lower extremity weakness and gait, and 79% had decreased painful dysesthesias. Median time to symptomatic improvement was least for pain (1 month), then motor (2.3 months), and then urinary symptoms (4.3 months; p = 0.04). In patients demonstrating improvement, 96% improved within 6 months of surgery. Only 4% improved beyond 1-year postoperatively. In a multivariate analysis, the authors found that patients who presented with asymmetrical lower extremity weakness (p = 0.0021, hazard ratio 5.7) or lower extremity hyperreflexia (p = 0.037, hazard ratio = 4.1) were most likely to experience improvement in motor symptoms.

Conclusions

In the authors' experience, pain and motor and urinary dysfunction improve postoperatively in the majority of patients. The rate of symptomatic improvement was greatest for pain resolution, followed by motor, and then urinary improvement. Patients who experienced improvement in any symptom had done so by 6 months after tethered cord release. Patients with asymmetrical motor symptoms or lower extremity hyperreflexia at presentation were most likely to experience improvements in motor symptoms. These findings may help guide patient education and surgical decision-making.

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Ralph T. W. M. Thomeer, J. Marc C. van Dijk, and Wilco C. Peul

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Joseph C. Noggle, Daniel M. Sciubba, Clarke Nelson, Giannina L. Garcés-Ambrossi, Edward Ahn, and George I. Jallo

Object

Treatments for brain abscesses have typically involved invasive craniotomies followed by debridement. These methods often require large incisions with vast exposure and may be associated with high morbidity rates. For supraorbital lesions of the anterior and middle cranial fossa, minimally invasive craniotomies may limit exposure and decrease surgically related morbidity while allowing adequate debridement and decompression. The authors report their experience in treating frontal epidural abscesses in pediatric patients through minimally invasive supraciliary craniotomies over a 4-year period.

Methods

Three pediatric patients with frontal epidural abscesses underwent minimally invasive debridement procedures. Each procedure consisted of a supraciliary incision and a small craniotomy to expose the abscess. All patients underwent pre- and postoperative radiological evaluation including computed tomography and magnetic resonance imaging. Data were collected on preoperative characteristics, operative management, and postoperative outcomes.

Results

Two patients were male and 1 patient was female. The ages of the patients ranged from 6 to 10 years (mean 8 years). A frontal abscess was diagnosed in all patients, and all were treated surgically without perioperative complications. Microbes cultured postoperatively included methicillin-resistant Staphylococcus aureus in 2 patients and Staphylococcus viridans in 1 patient. The mean follow-up duration was 12.3 months. No neurological or vascular complications were noted during follow-up. All patients were treated with antibiotics postoperatively and experienced resolution of symptoms and excellent outcomes.

Conclusions

Frontal epidural abscesses can be adequately and safely debrided via a minimally invasive supraciliary craniotomy. This approach has a cosmetic benefit and may decrease approach-related morbidity.

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Daniel M. Sciubba, Kaisorn L. Chaichana, Graeme F. Woodworth, Matthew J. McGirt, Ziya L. Gokaslan, and George I. Jallo

Object

The indications remain unclear for fusion at the time of cervical laminectomy for intradural tumor resection. To identify patients who may benefit from initial fusion, the authors assessed clinical, radiological/imaging, and operative factors associated with subsequent symptomatic cervical instability requiring fusion after cervical laminectomy for intradural tumor resection.

Methods

The authors reviewed 10 years of data obtained in patients who underwent cervical laminectomy without fusion for intradural tumor resection and who had normal spinal stability and alignment preoperatively. The association of pre- and intraoperative variables with the subsequent need for fusion for progressive symptomatic cervical instability was assessed using logistic regression analysis, and percentages were compared using Fisher exact tests when appropriate.

Results

Thirty-two patients (mean age 41 ± 17 years) underwent cervical laminectomy without fusion for resection of an intradural tumor (18 intramedullary and 14 extramedullary). Each increasing number of laminectomies performed was associated with a 3.1-fold increase in the likelihood of subsequent vertebral instability (odds ratio 3.114, 95% confidence interval 1.207–8.034, p = 0.02). At a mean follow-up interval of 25.2 months, 33% (4 of 12) of the patients who had undergone a ≥ 3-level laminectomy required subsequent fusion compared with 5% (1 of 20) who had undergone a ≤ 2-level laminectomy (p = 0.03). Four (36%) of 11 patients initially presenting with myelopathic motor disturbance required subsequent fusion compared with 1 (5%) of 21 presenting initially with myelopathic sensory or radicular symptoms (p = 0.02). Age, the presence of a syrinx, intramedullary tumor, C-2 laminectomy, C-7 laminectomy, and laminoplasty were not associated with subsequent symptomatic instability requiring fusion.

Conclusions

In the authors' experience with intradural cervical tumor resection, patients presenting with myelopathic motor symptoms or those undergoing a ≥ 3-level cervical laminectomy had an increased likelihood of developing subsequent symptomatic instability requiring fusion. A ≥ 3-level laminectomy with myelopathic motor symptoms may herald patients most likely to benefit from cervical fusion at the time of tumor resection.