Lali Sekhon and Neil Duggal
Joshua M. Ammerman and Matthew D. Ammerman
Neil Duggal, Sam Iskander and Robert R. Hammond
Object. It is recognized that cortical dysplasia (CD) is associated with an increased incidence of glioneuronal neoplasms. Among hypothetical considerations, there is the possibility that CD and other neuronal migration abnormalities harbor dysmature cells with the potential to give rise to glioneuronal neoplasms. Such cells, if present, would be reasonably expected to display immature features. The goal of the present study was to characterize the expression of nestin, a neuroepithelial precursor/stem cell antigen, in CD, along with other pathological and clinical features of this entity.
Methods. Clinical and surgical features of 10 recent cases meeting the histological criteria for CD were reviewed. Expressions of nestin, MAP2, neurofilament, and glial fibrillary acidic protein (GFAP) were assessed using immunohistochemical analysis and confocal scanning laser microscopy.
Immunoreactivity for both glial and neuronal antigens as well as nestin was found in a select group of cells within regions of CD. Immunohistochemical and confocal microscopic findings demonstrated that these cells with neuronal or ambiguous features are a mixed population, some of which are dysmature neurons (positive for nestin and MAP2), whereas others are astrocytic (positive for nestin and GFAP).
Conclusions. Further insight into the nature of nestin-positive neurons may shed light on the cause and pathogenesis of the associated glioneuronal tumors and the accompanying chronic seizures.
Michael D. Staudt, Doron Rabin, Ali A. Baaj, Neil R. Crawford and Neil Duggal
There are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.
Fourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.
Range of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).
Foraminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.
Balraj S. Jhawar, Demytra Mitsis and Neil Duggal
Perhaps the single greatest error that a surgeon hopes to avoid is operating at the wrong site. In this report, the authors describe the incidence and possible determinants of incorrect-site surgery (ICSS) among neurosurgeons.
The authors asked neurosurgeons to complete an anonymous survey. These surgeons were asked to report the number of craniotomies and lumbar and cervical discectomies performed during the previous year, as well as whether ICSS had occurred. They were also asked detailed questions regarding the potential determinants of ICSS.
There was a 75% response rate and a 68% survey completion rate. Participating neurosurgeons performed 4695 lumbar and 2649 cervical discectomies, as well as 10,203 craniotomies. Based on this self-reporting, the incidence of wrong-level lumbar surgery was estimated to be 4.5 occurrences per 10,000 operations. The ICSSs per 10,000 cervical discectomies and craniotomies were 6.8 and 2.2, respectively. Neurosurgeons recognized fatigue, unusual time pressure, and emergent operations as factors contributing to ICSS. For spine surgery, in particular, unusual patient anatomy and a failure to verify the operative site by radiography were also commonly reported contributors.
Neurosurgical ICSSs do occur, but are rare events. Although there are significant limitations to the survey-based methodology, the data suggest that the prevention of such errors will require neurosurgeons to recognize risk factors and increase the use of intraoperative imaging.
Kayla Ryan, Sandy Goncalves, Robert Bartha and Neil Duggal
The authors used functional MRI to assess cortical reorganization of the motor network after chronic spinal cord compression and to characterize the plasticity that occurs following surgical intervention.
A 3-T MRI scanner was used to acquire functional images of the brain in 22 patients with reversible cervical spinal cord compression and 10 control subjects. Controls performed a finger-tapping task on 3 different occasions (baseline, 6-week follow-up, and 6-month follow-up), whereas patients performed the identical task before surgery and again 6 weeks and 6 months after spinal decompression surgery.
After surgical intervention, an increased percentage blood oxygen level–dependent signal and volume of activation was observed within the contralateral and ipsilateral motor network. The volume of activation of the contralateral primary motor cortex was associated with functional measures both at baseline (r = 0.55, p < 0.01) and 6 months after surgery (r = 0.55, p < 0.01). The percentage blood oxygen level–dependent signal of the ipsilateral supplementary motor area 6 months after surgery was associated with increased function 6 months after surgery (r = 0.48, p < 0.01).
Plasticity of the contralateral and ipsilateral motor network plays complementary roles in maintaining neurological function in patients with spinal cord compression and may be critical in the recovery phase following surgery.
Izabela Aleksanderek, Todd K. Stevens, Sandy Goncalves, Robert Bartha and Neil Duggal
The goal of this study was to compare the recovery of neuronal metabolism and functional reorganization in the primary motor cortex (M1) between mild and moderate cervical spondylotic myelopathy (CSM) following surgical intervention.
Twenty-eight patients with CSM underwent 3-T MRI scans that included spectroscopy and functional MRI, before surgery and 6 months postsurgery. The classification of severity was based on the modified Japanese Orthopaedic Association questionnaire. Mild and moderate myelopathy were defined by modified Japanese Orthopaedic Association scores > 12 of 18 (n = 15) and 9–12 (n = 13), respectively. Ten healthy control subjects underwent 2 MRI scans 6 months apart. Metabolite levels were measured in the M1 contralateral to the greater deficit side in patients with CSM and on both sides in the controls. Motor function was assessed using a right finger–tapping paradigm and analyzed with BrainVoyager QX.
Patients with mild CSM had a lower preoperative N-acetylaspartate to creatine (NAA/Cr) ratio compared with moderate CSM, suggesting mitochondrial dysfunction. Postsurgery, NAA/Cr in moderate CSM decreased to the levels observed in mild CSM. Preoperatively, patients with mild CSM had a larger volume of activation (VOA) in the M1 than those with moderate CSM. Postoperatively, the VOAs were comparable between the mild and moderate CSM groups and had shifted toward the primary sensory cortex.
The NAA/Cr ratio and VOA size in the M1 can be used to discriminate between mild and moderate CSM. Postsurgery, the metabolite profile of the M1 did not recover in either group, despite significant clinical improvement. The authors proposed that metabolic impairment in the M1 may trigger the recruitment of adjacent healthy cortex to achieve functional recovery.
Michael G. Fehlings
Izabela Kowalczyk, Bruno C. R. Lazaro, Marie Fink, Doron Rabin and Neil Duggal
Cervical arthroplasty has emerged as a means of preventing adjacent segment disease by preserving motion, restoring sagittal balance, and mimicking natural spinal kinematics. The purpose of this retrospective in vivo study was to characterize the impact of arthroplasty on sagittal balance and segmental kinematics of the cervical spine.
Sixty patients receiving the Bryan disc, ProDisc-C, or Prestige LP disc were retrospectively analyzed. Only single-level arthroplasty cases were included in this study. Lateral dynamic radiographs of the cervical spine were evaluated using quantitative measurement analysis software to determine the kinematics at the index level both preoperatively and 1 year postoperatively. Collected parameters included range of motion (ROM), disc angles, shell angles, anterior and posterior disc heights (ADHs/PDHs), translation, and center of rotation (COR). Preoperative and postoperative data were compared using the Student t-test, with p < 0.05 indicating significance.
The Bryan and Prestige LP discs preserved motion, whereas the ProDisc-C increased segmental ROM from extension to flexion. Following surgery, the Bryan disc exhibited significant shell angle kyphosis, while ProDisc-C and Prestige LP retained lordosis. Both ADHs and PDHs decreased following insertion of the Bryan disc. In contrast, the ProDisc-C increased the ADHs and PDHs by 80% and 52%, respectively, and the Prestige LP disc increased the ADHs and PDHs by 20%. Only the ProDisc-C demonstrated significant translation of 0.7 mm. The ProDisc-C shifted the COR x by 0.9 mm anteriorly, while the Prestige LP disc demonstrated a significant superior shift of 2.2 mm in COR y.
All discs adequately maintained ROM at the surgical level. The greatest difference among the 3 devices was in the disc height and index angle measurements.