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Pranay Soni, Jeremy G. Loss, Callan M. Gillespie, Robb W. Colbrunn, Richard Schlenk, Michael P. Steinmetz, Pablo F. Recinos, Edward C. Benzel, and Varun R. Kshettry

OBJECTIVE

The direct lateral approach is an alternative to the transoral or endonasal approaches to ventral epidural lesions at the lower craniocervical junction. In this study, the authors performed, to their knowledge, the first in vitro biomechanical evaluation of the craniovertebral junction after sequential unilateral C1 lateral mass resection. The authors hypothesized that partial resection of the lateral mass would not result in a significant increase in range of motion (ROM) and may not require internal stabilization.

METHODS

The authors performed multidirectional in vitro ROM testing using a robotic spine testing system on 8 fresh cadaveric specimens. We evaluated ROM in 3 primary movements (axial rotation [AR], flexion/extension [FE], and lateral bending [LB]) and 4 coupled movements (AR+E, AR+F, LB + left AR, and LB + right AR). Testing was performed in the intact state, after C1 hemilaminectomy, and after sequential 25%, 50%, 75%, and 100% C1 lateral mass resection.

RESULTS

There were no significant increases in occipital bone (Oc)–C1, C1–2, or Oc–C2 ROM after C1 hemilaminectomy and 25% lateral mass resection. After 50% resection, Oc–C1 AR ROM increased by 54.4% (p = 0.002), Oc LB ROM increased by 47.8% (p = 0.010), and Oc–C1 AR+E ROM increased by 65.8% (p < 0.001). Oc–C2 FE ROM increased by 7.2% (p = 0.016) after 50% resection; 75% and 100% lateral mass resection resulted in further increases in ROM.

CONCLUSIONS

In this cadaveric biomechanical study, the authors found that unilateral C1 hemilaminectomy and 25% resection of the C1 lateral mass did not result in significant biomechanical instability at the occipitocervical junction, and 50% resection led to significant increases in Oc–C2 ROM. This is the first biomechanical study of lateral mass resection, and future studies can serve to validate these findings.

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Joshua S. Catapano, Caleb Rutledge, Kavelin Rumalla, Kunal P. Raygor, Visish M. Srinivasan, Stefan W. Koester, Anna R. Kimata, Kevin L. Ma, Mohamed A. Labib, Robert F. Spetzler, and Michael T. Lawton

OBJECTIVE

The brainstem cavernous malformation (BSCM) grading system predicts neurological outcomes associated with microsurgical resection and assists neurosurgeons in selecting patients for treatment. The predictive accuracy of the BSCM grading system should be validated in a large cohort from high-volume centers to generalize its use.

METHODS

An external validation cohort comprised patients with a BSCM resected by the senior author (M.T.L.) since the publication of the BSCM grading system and those resected by another neurosurgeon (R.F.S.) over a 16-year period. Size, crossing the axial midpoint, the presence of a developmental venous anomaly, patient age, and timing of last hemorrhage were used to assign BSCM grades from 0 to VII. Poor neurological outcomes were recorded as modified Rankin Scale scores > 2 at last follow-up examination.

RESULTS

A total of 277 patients were included in the study. The average BSCM grade was 3.9, and the majority of BSCMs (181 patients, 65%) were intermediate grade (grades III–V). Outcomes were predicted by BSCM grade, with good outcomes observed in 47 of 54 patients (87%) with low-grade BSCMs, in 135 of 181 patients (75%) with intermediate-grade BSCMs, and in 21 of 42 patients (50%) with high-grade BSCMs. Conversely, proportions of patients with neurological deterioration increased with increasing BSCM grade, with worsening observed in 2 of 54 patients (4%) with low-grade BSCMs, in 29 of 181 patients (16%) with intermediate-grade BSCMs, and in 17 of 42 patients (40%) with high-grade BSCMs. In the chi-square analysis, high-grade BSCMs were associated with increased odds of neurological worsening compared to low- and intermediate-grade BSCMs (OR 5.0, 95% CI 2.4–10.4; p < 0.001). The receiver operating characteristic analysis demonstrated acceptable discrimination for predicting unfavorable functional outcomes (modified Rankin Scale score > 2) with an area under the curve of 0.74 (95% CI 0.68–0.80; p < 0.001).

CONCLUSIONS

This study validates the BSCM grading system in a large cohort of patients from two high-volume surgeons. BSCM grade predicted neurological outcomes with accuracy comparable to that of other grading systems in widespread use. The BSCM grading system establishes categories of low-, intermediate-, and high-grade BSCMs and a boundary or cutoff for surgery at BSCM grade V. BSCM grading guides the analysis of a particular patient’s condition, but treatment recommendations must be individualized, and neurosurgeons must calibrate BSCM grading to their own outcome results, unique abilities, and practices.

Free access

Shi-Zhou Zhao, Bang-Ping Qian, Ji-Chen Huang, Mu Qiao, Bin Wang, and Yong Qiu

OBJECTIVE

The aim of this study was to analyze the specific patterns and risk factors of sagittal reconstruction failure in ankylosing spondylitis (AS)–related thoracolumbar kyphosis after pedicle subtraction osteotomy (PSO).

METHODS

A retrospective study was performed in patients with AS and thoracolumbar kyphosis after lumbar PSO with a minimum follow-up of 2 years. Patients were classified as having successful realignment (group A), inadequate correction immediately postoperatively (group B), and sagittal decompensation during follow-up (group C) according to the immediately postoperative and latest follow-up sagittal vertical axis (SVA). Radiographic parameters and clinical outcomes were collected. Pelvic tilt (PT) was used to assess the magnitude of pelvic backward rotation. Hip structural damage and ossification of the anterior longitudinal ligament (ALL) at the proximal junction, PSO level, and distal junction were also evaluated on radiographs.

RESULTS

Overall, 109 patients with a mean age of 35.3 years were included. Patients in both group B (n = 16) and group C (n = 13) were older than those in group A (n = 80) (mean ages 43.6 vs 32.9 years, p < 0.011; and 39.2 vs 32.9 years, p = 0.018; respectively). Age (OR 1.102, p = 0.011), and preoperative PT (OR 1.171, p = 0.041) and SVA (OR 1.041, p = 0.016) were identified as independent risk factors of inadequate correction. Additionally, a higher distribution of patients with adequate ALL ossification at the PSO level was found in group B than in group A (37.5% vs 22.5%, p = 0.003). Age (OR 1.101, p = 0.011) and preoperative SVA (OR 1.013, p = 0.020) were identified as independent risk factors of sagittal decompensation. Furthermore, compared with group A, group C showed a higher distribution of patients with severe hip structural damage (15.4% vs 0, p = 0.018) and higher incidences of rod fracture (RF) (38.5% vs 8.8%, p = 0.011) and pseudarthrosis (15.4% vs 0, p = 0.018). Additionally, the incidence of RF (19.6% vs 6.9%, p = 0.045) and changes in the proximal junctional angle (0.5° vs 2.2°, p = 0.027) and the distal junctional angle (0.3° vs 2.2°, p = 0.019) were lower during follow-up in patients with adequate ALL ossification than in those without adequate ossification.

CONCLUSIONS

Sagittal reconstruction failure in patients with AS could be attributed to inadequate correction immediately after surgery (14.7%) and sagittal decompensation during follow-up (11.9%). Adequate ALL ossification was a risk factor of inadequate correction. However, adequate ALL ossification could decrease the development of RF and relieve the junctional kyphotic change during follow-up. Older age and greater baseline SVA were independent risk factors for both inadequate correction and sagittal decompensation.

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Panagiotis Mastorakos, I. Jonathan Pomeraniec, Jean-Paul Bryant, Prashant Chittiboina, and John D. Heiss

OBJECTIVE

Chronic adhesive spinal arachnoiditis (SA) is a complex disease process that results in spinal cord tethering, CSF flow blockage, intradural adhesions, spinal cord edema, and sometimes syringomyelia. When it is focal or restricted to fewer than 3 spinal segments, the disease responds well to open surgical approaches. More extensive arachnoiditis extending beyond 4 spinal segments has a much worse prognosis because of less adequate removal of adhesions and a higher propensity for postoperative scarring and retethering. Flexible neuroendoscopy can extend the longitudinal range of the surgical field with a minimalist approach. The authors present a cohort of patients with severe cervical and thoracic arachnoiditis and myelopathy who underwent flexible endoscopy to address arachnoiditis at spinal segments not exposed by open surgical intervention. These observations will inform subsequent efforts to improve the treatment of extensive arachnoiditis.

METHODS

Over a period of 3 years (2017–2020), 10 patients with progressive myelopathy were evaluated and treated for extensive SA. Seven patients had syringomyelia, 1 had spinal cord edema, and 2 had spinal cord distortion. Surgical intervention included 2- to 5-level thoracic laminectomy, microscopic lysis of adhesions, and then lysis of adhesions at adjacent spinal levels performed using a rigid or flexible endoscope. The mean follow-up was 5 months (range 2–15 months). Neurological function was examined using standard measures. MRI was used to assess syrinx resolution.

RESULTS

The mean length of syringes was 19.2 ± 10 cm, with a mean maximum diameter of 7.0 ± 2.9 mm. Patients underwent laminectomies averaging 3.7 ± 0.9 (range 2–5) levels in length followed by endoscopy, which expanded exposure by an average of another 2.4 extra segments (6.1 ± 4.0 levels total). Endoscopic dissection of extensive arachnoiditis in the dorsal subarachnoid space proceeded through a complex network of opaque arachnoidal bands and membranes bridging from the dorsal dura mater to the spinal cord. In less severely problematic areas, the arachnoid membrane was transparent and attached to the spinal cord through multifocal arachnoid adhesions bridging the subarachnoid space. The endoscope did not compress or injure the spinal cord.

CONCLUSIONS

Intrathecal endoscopy allowed visual assessment and safe removal of intradural adhesions beyond the laminectomy margins. Further development of this technique should improve its effectiveness in opening the subarachnoid space and untethering the spinal cord in cases of extensive chronic adhesive SA.

Open access

Claudio H. F. Vidal, Yoav Hahn, Mariana C. Leal, Kiara Medeiros, Gabriela F. Hazin, and Caetano J. Coimbra

Hearing preservation is a cornerstone in the management of intracanalicular vestibular schwannomas. This video demonstrates a middle fossa approach to an intracanalicular schwannoma and highlights some technical and anatomical nuances relevant to the procedure. The patient had sustained hearing preservation in the postoperative period. There are potential benefits in favor of the middle fossa when the tumor reaches the fundus of the internal auditory canal, but the surgeon’s individual experience plays a decisive role in the choice of approach.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21121

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Kristin Huntoon, Matthew J. Shepard, Rimas V. Lukas, Ian E. McCutcheon, Anthony B. Daniels, and Ashok R. Asthagiri

OBJECTIVE

Hemangioblastomas are a frequent underlying cause of neurological morbidity and death in patients with von Hippel–Lindau disease (VHL). Although these benign tumors can cause significant neurological debility when undetected and untreated, unified evidence-based surveillance recommendations for VHL patients have not been established. To develop consensus recommendations, the VHL Alliance established an expert committee, named the International VHL Surveillance Guidelines Consortium, to define surveillance recommendations.

METHODS

The Central Nervous System (CNS) Hemangioblastoma Subcommittee of the Guidelines Consortium was formed as a multidisciplinary team of experts in the diagnosis and management of hemangioblastomas. Recommendations were formulated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) and National Comprehensive Cancer Network Categories of Evidence and Consensus categorization after a comprehensive literature review.

RESULTS

Published studies (n = 49) that discussed age at onset, MRI frequency, natural history of VHL, and the risks and benefits of surveillance were analyzed. Based on this analysis, the authors recommend that clinical evaluation (yearly) be used as the primary screening tool for hemangioblastomas in VHL. The subcommittee suggests that screening be performed between the ages of 11 and 65 years, or with the onset of symptoms, for synchronicity with other testing regimens in VHL. The subcommittee also recommends that baseline MRI be first performed at the age of 11 years (suggested 2B, level of evidence D) or after identification of neurological symptoms or signs (if earlier) and continue every 2 years (recommended 2A, level of evidence A).

CONCLUSIONS

The CNS Hemangioblastoma Subcommittee of the International VHL Surveillance Guidelines Consortium here proposes guidelines that aim to increase the early detection of VHL-associated hemangioblastomas to reduce their morbidity and mortality.

Open access

Robert M. Conway, Nathan C. Tu, Pedrom C. Sioshansi, Dennis I. Bojrab II, Jeffrey T. Jacob, and Seilesh C. Babu

Cochlear implantation (CI) has become an option for the treatment of hearing loss after translabyrinthine resection of vestibular schwannomas. The surgical video presents the case of a 67-year-old male who had translabyrinthine resection of vestibular schwannoma with simultaneous CI and closure with a hydroxyapatite (HA) cement cranioplasty. HA cement cranioplasty can be utilized in place of abdominal fat graft for the closure of translabyrinthine approaches with similar efficacy and complication profile. To the authors’ knowledge, this is the first reported case of a simultaneous CI and translabyrinthine resection of vestibular schwannoma with HA cement cranioplasty.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID211

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Doniel Drazin, J. Patrick Johnson, Tiffany Perry, Michael Y. Wang, Jens R. Chapman, and Bernhard Meyer

Open access

Michael J. Link, Isaac Yang, Fred G. Barker II, Amir Samii, and Philip V. Theodosopoulos

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Joseph H. Piatt