Idiopathic ventral spinal cord herniation is a rare condition that has been increasingly reported in the last decade. The natural history and optimal management have yet to be defined. Therefore, debate exists regarding the pathogenesis and surgical management of this condition. The purpose of this review article is to further educate neurosurgeons about the surgical techniques and outcomes associated with treating this rare and often misdiagnosed condition.
John H. Shin and Ajit A. Krishnaney
John H. Shin, Michael P. Steinmetz, Edward C. Benzel, and Ajit A. Krishnaney
Ossification of the posterior longitudinal ligament is a common cause of radiculopathy and myelopathy that often requires surgery to achieve decompression of the neural elements. With the evolution of surgical technique and a greater understanding of the biomechanics of cervical deformity, the criteria for selecting one approach over the other has been the subject of increased study and remains controversial. Ventral approaches typically consist of variations of the cervical corpectomy, whereas dorsal approaches include a wide range of techniques including laminoplasty, laminectomy, and laminectomy with instrumented fusion. Herein, the features and limitations of these approaches are reviewed with an emphasis on complications and outcomes.
Ron I. Riesenburger, G. Alexander Jones, Marie Roguski, and Ajit A. Krishnaney
The goal of this study was to characterize the anatomy relevant to placement of crossing C-2 translaminar screws, including morphometric data, and to evaluate the risk of violating the vertebral artery (VA) during the screw placement. Placement of bilateral crossing C-2 translaminar screws has become an increasingly popular method for dorsal C-2 instrumentation as it is felt to avoid the known risk of VA injury associated with C1–2 transarticular screw fixation and C-1 lateral mass–C-2 pars screw fixation.
The source images from 50 CT angiograms of the neck obtained from October to November 2007 were studied. Digital imaging software was used to measure lamina thickness and maximum screw length, perform angulation of screw trajectories in the axial plane, and evaluate the potential for VA injury. In cases where the VA could be injured, the distance between the maximal screw length and artery was measured. Logistic regression was performed to evaluate lamina width, axial angle, and screw length for predicting the potential for VA injury.
Mean lamina thickness, axial angle, and maximal screw length were determined for 100 laminae, and a potential for VA injury was noted in 55 laminae. The anatomically defined ideal screw length was longer in laminae with potential for VA injury than in laminae with no apparent risk (35.2 vs 33.6 mm, p = 0.0131). Only increasing optimal screw length was noted to be a statistically significant predictor of potential VA injury (p = 0.0159). The “buffer zone” (the distance between an optimally placed screw and the VA) was 5.6 ± 1.9 mm (mean ± SD, range 1.8–11.4 mm). A screw limited to 28 mm in length appeared to be safe in all laminae studied.
Crossing C-2 translaminar screws have been reported to be safe and effective. In addition to morphometric characteristics, the authors have found that screws placed in this trajectory could jeopardize the vertebral arteries in the foramen transversarium or the C1–2 interval. A C-2 translaminar screw limited to 28 mm in length appeared to be safe in all 100 screw trajectories studied in this series.
Vikram B. Chakravarthy, Hammad A. Khan, Shaarada Srivatsa, Todd Emch, Samuel T. Chao, and Ajit A. Krishnaney
Separation surgery followed by spine stereotactic radiosurgery (SSRS) has been shown to achieve favorable rates of local tumor control and patient-reported outcomes in patients with metastatic epidural spinal cord compression (MESCC). However, rates and factors associated with adjacent-level tumor progression (ALTP) in this population have not yet been characterized. The present study aimed to identify factors associated with ALTP and examine its association with overall survival (OS) in patients receiving surgery followed by radiosurgery for MESCC.
Thirty-nine patients who underwent separation surgery followed by SSRS for MESCC were identified using a prospectively collected database and were retrospectively reviewed. Radiological measurements were collected from preoperative, postoperative, and post-SSRS MRI. Statistical analysis was conducted using the Kaplan-Meier product-limit method and Cox proportional hazards test. Subgroup analysis was conducted for patients who experienced ALTP into the epidural space (ALTP-E).
The authors’ cohort included 39 patients with a median OS of 14.7 months (range 2.07–96.3 months). ALTP was observed in 16 patients (41.0%) at a mean of 6.1 ± 5.4 months postradiosurgery, of whom 4 patients (10.3%) experienced ALTP-E. Patients with ALTP had shorter OS (13.0 vs 17.1 months, p = 0.047) compared with those without ALTP. Factors associated with an increased likelihood of ALTP included the amount of bone marrow infiltrated by tumor at the index level, amount of residual epidural disease following separation surgery, and prior receipt of radiotherapy at the index level (p < 0.05). Subgroup analysis revealed that primary tumor type, amount of preoperative epidural disease, time elapsed between surgery and radiosurgery, and prior receipt of radiotherapy at the index level were significantly associated with ALTP-E (p < 0.05).
To the authors’ knowledge, this study is the first to identify possible risk factors for ALTP, and they suggest that it may be associated with shorter OS in patients receiving surgery followed by radiosurgery for MESCC. Future studies with higher power should be conducted to further characterize factors associated with ALTP in this population.
Vikram B. Chakravarthy, Hana Yokoi, Daniel J. Coughlin, Mariel R. Manlapaz, and Ajit A. Krishnaney
Enhanced recovery after surgery (ERAS) protocols have been shown to be effective at reducing perioperative morbidity and costs while improving outcomes. To date, spine surgery protocols have been limited in scope, focusing only on specific types of procedures or specific parts of the surgical episode. The authors describe the creation and implementation of one of the first comprehensive ERAS protocols for spine surgery. The protocol is unique in that it has a comprehensive perioperative paradigm encompassing the entire surgical period that is tailored based on the complexity of each individual spine patient.
Michael P. Steinmetz, Jared Miller, Ann Warbel, Ajit A. Krishnaney, William Bingaman, and Edward C. Benzel
The cervicothoracic junction (CTJ) is the transitional region between the cervical and thoracic sections of the spinal axis. Because it is a transitional zone between the mobile lordotic cervical and rigid kyphotic thoracic spines, the CTJ is a region of potential instability. This potential for instability may be exaggerated by surgical intervention.
A retrospective review of all patients who underwent surgery involving the CTJ in the Department of Neurosurgery at the Cleveland Clinic Foundation during a 5-year period was performed. The CTJ was strictly defined as encompassing the C-7 vertebra and C7–T1 disc interspace. Patients were examined after surgery to determine if treatment had failed. Failure was defined as construct failure, deformity (progression or de novo), or instability. Variables possibly associated with treatment failure were analyzed. Statistical comparisons were performed using the Fisher exact test.
Between January 1998 and November 2003, 593 CTJ operations were performed. Treatment failed in 14 patients. Of all variables studied, failure was statistically associated with laminectomy and multilevel ventral corpectomies with fusion across the CTJ. Other factors statistically associated with treatment failure included histories of cervical surgery, tobacco use, and surgery for the correction of deformity.
The CTJ is a vulnerable region, and this vulnerability is exacerbated by surgery. Results of the present study indicate that laminectomy across the CTJ should be supplemented with instrumentation (and fusion). Multilevel ventral corpectomies across the CTJ should also be supplemented with dorsal instrumentation. Supplemental instrumentation should be considered for patients who have undergone prior cervical surgery, have a history of tobacco use, or are undergoing surgery for deformity correction.
Cervical spinal cord delivery of a rabies G protein pseudotyped lentiviral vector in the SOD-1 transgenic mouse
Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004
Kiana Tanase, Qingshan Teng, Ajit A. Krishnaney, James K. Liu, Mary E. Garrity-Moses, and Nicholas M. Boulis
Object. Lentiviral vectors may constitute a vehicle for long-term therapeutic gene expression in the spinal cord. In amyotrophic lateral sclerosis, spinal cord sclerosis and altered axonal transport pose barriers to therapeutic gene distribution. In the present study the authors characterize gene expression distribution and the behavioral impact of the rabies G (RabG) protein pseudotyped lentiviral vector EIAV.LacZ through cervical spinal cord injection in control and Cu/Zn superoxide dismutase—1 (SOD-1) transgenic mice.
Methods. Seven-week-old SOD-1 transgenic mice and their wild-type littermates underwent exposure of the cervicomedullary junction and microinjection of RabG.EIAV.LacZ or vehicle. The Basso-Beattie-Bresnahan locomotor score, grip strength meter, and Rotarod assays were used to assess the effects of disease progression, spinal cord microinjection, and lentiviral gene expression. Spinal cords were removed when the mice were in the terminal stage of the disease. The distribution of LacZ gene expression was histologically evaluated and quantified.
Direct cervical spinal cord microinjection of RabG.EIAV.LacZ results in extensive central nervous system uptake in SOD-1 transgenic mice; these findings were statistically similar to those in wild-type mice (p > 0.05). Gene expression lasts for the duration of the animal's survival (132 days). The SOD-1 mutation does not prevent retrograde axonal transport of the vector. Three behavioral assays were used to demonstrate that long-term gene expression does not alter sensorimotor function. In comparison with normative data, vector injection and transgene expression do not accelerate disease progression.
Conclusions. Direct spinal cord injection of RabG.EIAV vectors represents a feasible method for delivering therapeutic genes to upper cervical spinal cord and brainstem motor neurons. Distribution is not affected by the SOD-1 mutation or disease phenotype.
Wajd N. Al-Holou, Thomas J. Wilson, Zarina S. Ali, Ryan P. Brennan, Kelly J. Bridges, Tannaz Guivatchian, Ghaith Habboub, Ajit A. Krishnaney, Giuseppe Lanzino, Kendall A. Snyder, Tracy M. Flanders, Khoi D. Than, and Aditya S. Pandey
Gastrostomy tube placement can temporarily seed the peritoneal cavity with bacteria and thus theoretically increases the risk of shunt infection when the two procedures are performed contemporaneously. The authors hypothesized that gastrostomy tube placement would not increase the risk of ventriculoperitoneal shunt infection. The object of this study was to test this hypothesis by utilizing a large patient cohort combined from multiple institutions.
A retrospective study of all adult patients admitted to five institutions with a diagnosis of aneurysmal subarachnoid hemorrhage between January 2005 and January 2015 was performed. The primary outcome of interest was ventriculoperitoneal shunt infection. Variables, including gastrostomy tube placement, were tested for their association with this outcome. Standard statistical methods were utilized.
The overall cohort consisted of 432 patients, 47% of whom had undergone placement of a gastrostomy tube. The overall shunt infection rate was 9%. The only variable that predicted shunt infection was gastrostomy tube placement (p = 0.03, OR 2.09, 95% CI 1.07–4.08), which remained significant in the multivariate analysis (p = 0.04, OR 2.03, 95% CI 1.04–3.97). The greatest proportion of shunts that became infected had been placed more than 2 weeks (25%) and 1–2 weeks (18%) prior to gastrostomy tube placement, but the temporal relationship between shunt and gastrostomy was not a significant predictor of shunt infection.
Gastrostomy tube placement significantly increases the risk of ventriculoperitoneal shunt infection.
Rupesh Kotecha, Martin C. Tom, Mihir Naik, Lilyana Angelov, Edward C. Benzel, Chandana A. Reddy, Richard A. Prayson, Iain Kalfas, Richard Schlenk, Ajit Krishnaney, Michael P. Steinmetz, William Bingaman, John H. Suh, and Samuel T. Chao
The authors sought to describe the long-term recurrence patterns, prognostic factors, and effect of adjuvant or salvage radiotherapy (RT) on treatment outcomes for patients with spinal myxopapillary ependymoma (MPE).
The authors reviewed a tertiary institution IRB-approved database and collected data regarding patient, tumor, and treatment characteristics for all patients treated consecutively from 1974 to 2015 for histologically confirmed spinal MPE. Key outcomes included relapse-free survival (RFS), postrecurrence RFS, failure patterns, and influence of timing of RT on recurrence patterns. Cox proportional hazards regression and Kaplan-Meier analyses were utilized.
Of the 59 patients included in the study, the median age at initial surgery was 34 years (range 12–74 years), 30 patients (51%) were female, and the most common presenting symptom was pain (n = 52, 88%). Extent of resection at diagnosis was gross-total resection (GTR) in 39 patients (66%), subtotal resection (STR) in 15 (25%), and unknown in 5 patients (9%). After surgery, 10 patients (17%) underwent adjuvant RT (5/39 GTR [13%] and 5/15 STR [33%] patients). Median follow-up was 6.2 years (range 0.1–35.3 years). Overall, 20 patients (34%) experienced recurrence (local, n = 15; distant, n = 5). The median RFS was 11.2 years (95% CI 77 to not reached), and the 5- and 10-year RFS rates were 72.3% (95% CI 59.4–86.3) and 54.0% (95% CI, 36.4–71.6), respectively.
STR was associated with a higher risk of recurrence (HR 6.45, 95% CI 2.15–19.23, p < 0.001) than GTR, and the median RFS after GTR was 17.2 years versus 5.5 years after STR. Adjuvant RT was not associated with improved RFS, regardless of whether it was delivered after GTR or STR. Of the 20 patients with recurrence, 12 (60%) underwent salvage treatment with surgery alone (GTR, n = 6), 4 (20%) with RT alone, and 4 (20%) with surgery and RT. Compared to salvage surgery alone, salvage RT, with or without surgery, was associated with a significantly longer postrecurrence RFS (median 9.5 years vs 1.6 years; log-rank, p = 0.006).
At initial diagnosis of spinal MPE, GTR is key to long-term RFS, with no benefit to immediate adjuvant RT observed in this series. RT at the time of recurrence, however, is associated with a significantly longer time to second disease recurrence. Surveillance imaging of the entire neuraxis remains crucial, as distant failure is not uncommon in this patient population.
Shireen Parsai, Aditya Juloori, Lilyana Angelov, Jacob G. Scott, Ajit A. Krishnaney, Inyang Udo-Inyang, Tingliang Zhuang, Peng Qi, Matthew Kolar, Peter Anderson, Stacey Zahler, Samuel T. Chao, John H. Suh, and Erin S. Murphy
There are limited data on spine stereotactic radiosurgery (SRS) in treating adolescent and young adult (AYA) patients. SRS has the advantages of highly conformal radiation dose delivery in the upfront and retreatment settings, means for dose intensification, and administration over a limited number of sessions leading to a decreased treatment burden. In this study, the authors report the oncological and toxicity outcomes for AYA patients with metastatic sarcoma treated with spine radiosurgery and provide clinicians a guide for considerations in dose, volume, and fractionation.
An institutional review board–approved database of patients treated with SRS in the period from October 2014 through December 2018 was queried. AYA patients, defined by ages 15–29 years, who had been treated with SRS for spine metastases from Ewing sarcoma or osteosarcoma were included in this analysis. Patients with follow-ups shorter than 6 months after SRS were excluded. Local control, overall survival, and toxicity were reported.
Seven patients with a total of 11 treated lesions were included in this study. Median patient age was 20.3 years (range 15.1–26.1 years). Three patients had Ewing sarcoma (6 lesions) and 4 patients had osteosarcoma (5 lesions). The median dose delivered was 35 Gy in 5 fractions (range 16–40 Gy, 1–5 fractions). The median follow-up was 11.1 months (range 6.8–26.0 months). Three local failures were observed within the follow-up period. No acute grade 3 or greater toxicity was observed. One patient developed late grade 3 toxicity consisting of radiation enteritis. This patient had previously received radiation to an overlapping volume with conventional fractionation. SRS re-irradiation for this patient was also performed concurrently with chemotherapy administration. No late grade 4 or higher toxicities were observed. No pain flare or vertebral compression fracture was observed. Three patients died within the follow-up period.
SRS for spine metastases from Ewing sarcoma and osteosarcoma can be considered as a treatment option in AYA patients and is associated with acceptable toxicity rates. Further studies must be conducted to determine long-term local control and toxicity for this treatment modality.