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1.  A New Measure for Monitoring Intraoperative Somatosensory Evoked Potentials 
To propose a new measure for effective monitoring of intraoperative somatosensory evoked potentials (SEP) and to validate the feasibility of this measure for evoked potentials (EP) and single trials with a retrospective data analysis study.
The proposed new measure (hereafter, a slope-measure) was defined as the relative slope of the amplitude and latency at each EP peak compared to the baseline value, which is sensitive to the change in the amplitude and latency simultaneously. We used the slope-measure for EP and single trials and compared the significant change detection time with that of the conventional peak-to-peak method. When applied to single trials, each single trial signal was processed with optimal filters before using the slope-measure. In this retrospective data analysis, 7 patients who underwent cerebral aneurysm clipping surgery for unruptured aneurysm middle cerebral artery (MCA) bifurcation were included.
We found that this simple slope-measure has a detection time that is as early or earlier than that of the conventional method; furthermore, using the slope-measure in optimally filtered single trials provides warning signs earlier than that of the conventional method during MCA clipping surgery.
Our results have confirmed the feasibility of the slope-measure for intraoperative SEP monitoring. This is a novel study that provides a useful measure for either EP or single trials in intraoperative SEP monitoring.
PMCID: PMC4303719  PMID: 25628803
Intraoperative neurophysiological monitoring; Somatosensory evoked potentials; Slope-measure; Single trials; Temporary clipping
2.  Preoperative Weakness and Demyelination of the Corticospinal Tract in Meningioma Patients : Changes in Diffusion Parameters Using Diffusion Tensor Imaging 
Differentiation of demyelination in white matter from axonal damage can be determined using diffusion tensor imaging (DTI). In this study using meningioma patients an attempt was made to evaluate the relationship between preoperative weakness and the changes of diffusion parameters in the corticospinal tract (CST) using DTI.
Twenty-six patients with meningioma were enrolled in this study. Eleven of them suffered from objective motor weakness and were classified as Group 1. The remaining 15 patients did not present motor weakness and were classified as Group 2. Fiber tractography and CST diffusion parameters were obtained using DTIStudio. The ratios (lesion side mean value/contralateral side mean value) of CST diffusion parameters were compared with 1.0 as a test value using a one-sample t-test.
In Group 1, fractional anisotropy (FA), tensor trace (TT), and radial diffusivity (RD, λ2 and λ3) of the CST were significantly different between two hemispheres, but axial diffusivity (AD, λ1) of the CST was not significantly different between two hemispheres. In Group 2, FA and λ3 of CST did not differ significantly between the hemispheres. In Group 2, TT, λ1, and λ2 of CST in the ipsilateral hemisphere were significantly higher than those of the unaffected hemisphere. However, the differences were small.
Motor weakness was related to a low FA and high TT resulting from increased RD of the CST fibers. CST diffusion changes in patients with weakness are similar to those for demyelination.
PMCID: PMC4130952  PMID: 25132933
Corticospinal tract; Diffusion tensor imaging; Weakness; Demyelination; Diffusion
3.  The Impact of Menopause on Bone Fusion after the Single-Level Anterior Cervical Discectomy and Fusion 
To evaluate the successful fusion rate in postmenopausal women with single-level anterior cervical discectomy and successful fusion (ACDF) and identify the significant factors related to bone successful fusion in pre- and postmenopausal women.
From July 2004 to December 2010, 108 consecutive patients who underwent single-level ACDF were prospectively selected as candidates. Among these, the charts and radiological data of 39 women were reviewed retrospectively. These 39 women were divided into two groups : a premenopausal group (n=11) and a postmenopausal group (n=28). To evaluate the significant factors affecting the successful fusion rate, the following were analyzed : the presence of successful fusion, successful fusion type, age, operated level, bone mineral density, graft materials, stand-alone cage or plating with autologous iliac bone, subsidence, adjacent segment degeneration, smoking, diabetes mellitus, and renal disease.
The successful fusion rates of the pre- and postmenopausal groups were 90.9% and 89.2%, respectively. There was no significant difference in the successful fusion rate or successful fusion type between the two groups. In the postmenopausal group, three patients (10.8%) had successful fusion failure. In the postmenopausal group, age and subsidence significantly affected the successful fusion rate (p=0.016 and 0.011, respectively), and the incidence of subsidence in patients with a cage was higher than that in patients with a plate (p=0.030).
Menopausal status did not significantly affect bone successful fusion in patients with single-level ACDF. However, in older women with single-level ACDF, the combination of use of a cage and subsidence may unfavorably affect successful fusion.
PMCID: PMC3921277  PMID: 24527192
Menopause; Cervical; Discectomy; Successful fusion; Bone mineral density
4.  Conventional Posterior Approach without Far Lateral Approach for Ventral Foramen Magnum Meningiomas 
We present our experience of conventional posterior approach without fat lateral approach for ventral foramen magnum (FM) meningioma (FM meningioma) and tried to evaluate the approach is applicable to ventral FM meningioma.
From January 1999 to March 2011, 11 patients with a ventral FM meningioma underwent a conventional posterior approach without further extension of lateral bony window. The tumor was removed through a working space between the dura and arachnoid membrane at the cervicomedullary junction with minimal retraction of medulla, spinal cord or cerebellum. Care should be taken not to violate arachnoid membrane.
Preoperatively, six patients were of Nurick grade 1, three were of grade 2, and two were of grade 3. Median follow-up period was 55 months (range, 20-163 months). The extent of resection was Simpson grade I in one case and Simpson grade II in remaining 10 cases. Clinical symptoms improved in eight patients and stable in three patients. There were no recurrences during the follow-up period. Postoperative morbidities included one pseudomeningocele and one transient dysphagia with dysarthria.
Ventral FM meningiomas can be removed gross totally using a posterior approach without fat lateral approach. The arachnoid membrane can then be exploited as an anatomical barrier. However, this approach should be taken with a thorough understanding of its anatomical limitation.
PMCID: PMC3873348  PMID: 24379942
Foramen magnum; Meningioma; Surgery
5.  Correlation between Bone Mineral Density Measured by Dual-Energy X-Ray Absorptiometry and Hounsfield Units Measured by Diagnostic CT in Lumbar Spine 
Use of quantitative computed tomography (CT) to evaluate bone mineral density was suggested in the 1970s. Despite its reliability and accuracy, technical shortcomings restricted its usage, and dual-energy X-ray absorptiometry (DXA) became the gold standard evaluation method. Advances in CT technology have reduced its previous limitations, and CT evaluation of bone quality may now be applicable in clinical practice. The aim of this study was to determine if the Hounsfield unit (HU) values obtained from CT correlate with patient age and bone mineral density.
A total of 128 female patients who underwent lumbar CT for back pain were enrolled in the study. Their mean age was 66.4 years. Among them, 70 patients also underwent DXA. The patients were stratified by decade of life, forming five age groups. Lumbar vertebrae L1-4 were analyzed. The HU value of each vertebra was determined by averaging three measurements of the vertebra's trabecular portion, as shown in consecutive axial CT images. The HU values were compared between age groups, and correlations of HU value with bone mineral density and T-scores were determined.
The HU values consistently decreased with increasing age with significant differences between age groups (p<0.001). There were significant positive correlations (p<0.001) of HU value with bone mineral density and T-score.
The trabecular area HU value consistently decreases with age. Based on the strong positive correlation between HU value and bone mineral density, CT-based HU values might be useful in detecting bone mineral diseases, such as osteoporosis.
PMCID: PMC3873350  PMID: 24379944
Hounsfield unit; Computed tomography; Bone mineral density; T-score
6.  Supratentorial Intracerebral Schwannoma : Its Fate and Proper Management 
Intracerebral schwannomas are rare and there have been none reported in Korea. We present the case of a 25-year-old man with newly developed right-side weakness and recent seizure aggravation. His seizures started approximately 9 years prior to admission. At that time, a 1 cm diameter intra-axial enhancing mass at the left precentral gyrus was found on magnetic resonance image (MRI). After 9 years of observation and treatment with antiepileptic medication, an MRI taken due to symptom aggravation revealed peri-tumoral cyst formation with tumor enlargement. The tumor was surgically removed. Subsequently, right-side weakness diminished and there was good seizure control. Pathologic diagnosis was schwannoma. Schwannoma is a very rare tumor and there are no pathognomonic findings on radiologic images; thus, it is challenging to make a correct diagnosis. However, considering the natural course and excellent prognosis after surgical treatment of this kind of intra-axial mass with benign features, early surgery for diagnosis and proper treatment is highly recommended.
PMCID: PMC3841278  PMID: 24294459
Intracerebral schwannoma; Supratentorial; Precentral gyrus; Treatment; Seizure
7.  Magnetoencephalography Interictal Spike Clustering in Relation with Surgical Outcome of Cortical Dysplasia 
The aim of this study was to devise an objective clustering method for magnetoencephalography (MEG) interictal spike sources, and to identify the prognostic value of the new clustering method in adult epilepsy patients with cortical dysplasia (CD).
We retrospectively analyzed 25 adult patients with histologically proven CD, who underwent MEG examination and surgical resection for intractable epilepsy. The mean postoperative follow-up period was 3.1 years. A hierarchical clustering method was adopted for MEG interictal spike source clustering. Clustered sources were then tested for their prognostic value toward surgical outcome.
Postoperative seizure outcome was Engel class I in 6 (24%), class II in 3 (12%), class III in 12 (48%), and class IV in 4 (16%) patients. With respect to MEG spike clustering, 12 of 25 (48%) patients showed 1 cluster, 2 (8%) showed 2 or more clusters within the same lobe, 10 (40%) showed 2 or more clusters in a different lobe, and 1 (4%) patient had only scattered spikes with no clustering. Patients who showed focal clustering achieved better surgical outcome than distributed cases (p=0.017).
This is the first study that introduces an objective method to classify the distribution of MEG interictal spike sources. By using a hierarchical clustering method, we found that the presence of focal clustered spikes predicts a better postoperative outcome in epilepsy patients with CD.
PMCID: PMC3539081  PMID: 23323167
Epilepsy; Cortical dysplasia; Magnetoencephalography; Hierarchical clustering; Surgical outcome
8.  The Role of Stereotactic Radiosurgery in Metastasis to the Spine 
The incidence and prevalence of spinal metastases are increasing, and although the role of radiation therapy in the treatment of metastatic tumors of the spine has been well established, the same cannot be said about the role of stereotactic radiosurgery. Herein, the authors present a systematic review regarding the value of spinal stereotactic radiosurgery in the management of spinal metastasis.
A systematic literature search for stereotactic radiosurgery of spinal metastases was undertaken. Grades of Recommendation, Assessment, Development, and Education (GRADE) working group criteria was used to evaluate the qualities of study datasets.
Thirty-one studies met the study inclusion criteria. Twenty-three studies were of low quality, and 8 were of very low quality according to the GRADE criteria. Stereotactic radiosurgery was reported to be highly effective in reducing pain, regardless of prior treatment. The overall local control rate was approximately 90%. Additional asymptomatic lesions may be treated by stereotactic radiosurgery to avoid further irradiation of neural elements and further bone-marrow suppression. Stereotactic radiosurgery may be preferred in previously irradiated patients when considering the radiation tolerance of the spinal cord. Furthermore, residual tumors after surgery can be safely treated by stereotactic radiosurgery, which decreases the likelihood of repeat surgery and accompanying surgical morbidities. Encompassing one vertebral body above and below the involved vertebrae is unnecessary. Complications associated with stereotactic radiosurgery are generally self-limited and mild.
In the management of spinal metastasis, stereotactic radiosurgery appears to provide high rates of tumor control, regardless of histologic diagnosis, and can be used in previously irradiated patients. However, the quality of literature available on the subject is not sufficient.
PMCID: PMC3291699  PMID: 22396835
Radiosurgery; Spinal metastasis; Spine surgery; Radiation therapy; Local control; Spine tumors
9.  Postoperative Survival and Ambulatory Outcome in Metastatic Spinal Tumors : Prognostic Factor Analysis 
The purposes of this study are to estimate postoperative survival and ambulatory outcome and to identify prognostic factors thereafter of metastatic spinal tumors in a single institute.
We reviewed the medical records of 182 patients who underwent surgery for a metastatic spinal tumor from January 1987 to January 2009 retrospectively. Twelve potential prognostic factors (age, gender, primary tumor, extent and location of spinal metastases, interval between primary tumor diagnosis and metastatic spinal cord compression, preoperative treatment, surgical approach and extent, preoperative Eastern Cooperative Oncology Group (ECOG) performance status, Nurick score, Tokuhashi and Tomita score) were investigated.
The median survival of the entire patients was 8 months. Of the 182 patients, 80 (44%) died within 6 months after surgery, 113 (62%) died within 1 year after surgery, 138 (76%) died within 2 years after surgery. Postoperatively 47 (26%) patients had improvement in ambulatory function, 126 (69%) had no change, and 9 (5%) had deterioration. On multivariate analysis, better ambulatory outcome was associated with being ambulatory before surgery (p=0.026) and lower preoperative ECOG score (p=0.016). Survival rate was affected by preoperative ECOG performance status (p<0.001) and Tomita score (p<0.001).
Survival after metastatic spinal tumor surgery was dependent on preoperative ECOG performance status and Tomita score. The ambulatory functional outcomes after surgery were dependent on preoperative ambulatory status and preoperative ECOG performance status. Thus, prompt decompressive surgery may be warranted to improve patient's survival and gait, before general condition and ambulatory function of patient become worse.
PMCID: PMC3218181  PMID: 22102952
Prognosis; Spinal metastasis; Surgery; Survival; Ambulatory outcome
10.  Unexpected Seizure Attack in a Patient with Spinal Metastasis Diagnosed as Posterior Reversible Encephalopathy Syndrome 
Seizure is a foreseeable risk in patients with brain lesion. However, seizure during treating non-brain lesion is not a familiar situation to neurosurgeon. Posterior reversible encephalopathy syndrome (PRES) is a relatively common situation after systemic chemotherapy. The aim of this study is to make neurosurgeons aware of this potential medical problem. A 52-year-old woman with advanced gastric cancer, presented with low back pain due to spinal metastasis at the 4th lumbar vertebra. Ten cycles of chemotherapy with FOLFOX (5-Fluoruracil/Oxaliplatin) had been completed 23 days ago. Two days before the planned operation, a generalized tonic clonic seizure occurred. She did not have a history of hypertension or seizure. The seizure was stopped with lorazepam 4mg. The brain magnetic resonance (MR) imaging showed high signal changes in both parieto-occipital lobes on the T2-weighted images, and these were partially enhanced, suggesting PRES. The surgery was preceded by treatment with an antiepileptic drug. The MR images, taken 1.5 months after the seizure, showed that the lesion was no longer present. At 3 month follow-up, no additional seizure attack occurred without any seizure medication. The possibility of a seizure attack should be considered if the patient has a history of chemotherapy.
PMCID: PMC3159886  PMID: 21892409
Posterior reversible encephalopathy syndrome; Seizure; Metastasis; Spine; Oxaliplatin
11.  Strategies of Spinal Fusion on Osteoporotic Spine 
The prevalence of osteoporosis has been increasing globally. Recently surgical indications for elderly patients with osteoporosis have been increasing. However, only few strategies are available for osteoporotic patients who need spinal fusion. Osteoporosis is a result of negative bone remodeling from enhanced function of the osteoclasts. Because bone formation is the result of coupling between osteoblasts and osteoclasts, anti-resorptive agents that induce osteoclast apoptosis may not be effective in spinal fusion surgery, necessitating new bone formation. Therefore, anabolic agents may be more suitable for osteoporotic patients who undergo spinal fusion surgery. The instrumentations and techniques with increased pullout strength may increase fusion rate through rigid fixation. Studies on new osteoinductive materials, methods to increase osteogenic cells, strengthened and biocompatible osteoconductive scaffolds are necessary to enable osteoporotic patients to undergo spinal fusion. When osteoporotic patients undergo spinal fusion, surgeons should consider appropriate osteoporosis medication, instrumentation and technique.
PMCID: PMC3158472  PMID: 21887387
Osteoporosis; Spine; Fusion; Osteoblast; Osteoclast
12.  Bone Mineral Density Changes after Ovariectomy in Rats as an Osteopenic Model : Stepwise Description of Double Dorso-Lateral Approach 
This study describes a method for inducing osteopenia using bilateral ovariectomy (OVX), which causes significant changes in bone mineral density (BMD) in rats.
Twenty-five 10-week-old female Sprague Dawley rats were used. Five rats were euthanized after two weeks, and BMD was measured in their femora. The other 20 rats were assigned to one of two groups : a sham group (n = 10), which underwent a sham operation, and an OVX group (n = 10), which underwent bilateral OVX at 12 weeks of age. After six weeks, five rats from each group were euthanized, and BMD was measured in their femora. The same procedures were performed in the remaining rats form each group eight weeks later.
The femur BMD was significantly lower in the six-week OVX group than in the six-week sham group, and in the eight-week OVX group than in the eight-week sham group.
Bilateral OVX is a safe method for creating an osteopenic rat model. The significant decrease in BMD appears six weeks after bilateral OVX.
PMCID: PMC2982907  PMID: 21113356
Animal model; Osteoporosis; Rat; Ovariectomy
13.  Functional Reorganization Associated with Semantic Language Processing in Temporal Lobe Epilepsy Patients after Anterior Temporal Lobectomy : A Longitudinal Functional Magnetic Resonance Image Study 
The focus of this study is brain plasticity associated with semantic aspects of language function in patients with medial temporal lobe epilepsy (mTLE).
Using longitudinal functional magnetic resonance imaging (fMRI), patterns of brain activation were observed in twelve left and seven right unilateral mTLE patients during a word-generation task relative to a pseudo-word reading task before and after anterior temporal section surgery.
No differences were observed in precentral activations in patients relative to normal controls (n = 12), and surgery did not alter the phonological-associated activations. The two mTLE patient groups showed left inferior prefrontal activations associated with semantic processing (word-generation > pseudo-word reading), as did control subjects. The amount of semantic-associated activation in the left inferior prefrontal region was negatively correlated with epilepsy duration in both patient groups. Following temporal resection, semantic-specific activations in inferior prefrontal region became more bilateral in left mTLE patients, but more left-lateralized in right mTLE patients. The longer the duration of epilepsy in the patients, the larger the increase in the left inferior prefrontal semantic-associated activation after surgery in both patient groups. Semantic activation of the intact hippocampus, which had been negatively correlated with seizure frequency, normalized after the epileptic side was removed.
These results indicate alternation of semantic language network related to recruitment of left inferior prefrontal cortex and functional recovery of the hippocampus contralateral to the epileptogenic side, suggesting an intra- and inter-hemispheric reorganization following surgery.
PMCID: PMC2817510  PMID: 20157373
fMRI; Language; Epilepsy; Brain plasticity; Hippocampus
14.  Localization of Broca's Area Using Functional MR Imaging: Quantitative Evaluation of Paradigms 
Functional magnetic resonance imaging (fMRI) is frequently used to localize language areas in a non-invasive manner. Various paradigms for presurgical localization of language areas have been developed, but a systematic quantitative evaluation of the efficiency of those paradigms has not been performed. In the present study, the authors analyzed different language paradigms to see which paradigm is most efficient in localizing frontal language areas.
Five men and five women with no neurological deficits participated (mean age, 24 years) in this study. All volunteers were right-handed. Each subject performed 4 tasks, including fixation (Fix), sentence reading (SR), pseudoword reading (PR), and word generation (WG). Fixation and pseudoword reading were used as contrasts. The functional area was defined as the area(s) with a t-value of more than 3.92 in fMRI with different tasks. To apply an anatomical constraint, we used a brain atlas mapping system, which is available in AFNI, to define the anatomical frontal language area. The numbers of voxels in overlapped area between anatomical and functional area were individually counted in the frontal expressive language area.
Of the various combinations, the word generation task was most effective in delineating the frontal expressive language area when fixation was used as a contrast (p<0.05). The sensitivity of this test for localizing Broca's area was 81% and specificity was 70%.
Word generation versus fixation could effectively and reliably delineate the frontal language area. A customized effective paradigm should be analyzed in order to evaluate various language functions.
PMCID: PMC2682117  PMID: 19444347
Functional MRI; Language; Paradigm; Quantitative evaluation
15.  Spinal Dural Arteriovenous Fistulas: Clinical Experience with Endovascular Treatment as a Primary Therapeutic Modality 
The aim of this study was to evaluate the efficacy of endovascular therapy as a primary treatment for spinal dural arteriovenous fistula (DAVF).
The authors reviewed 18 patients with spinal DAVFs for whom endovascular therapy was considered as an initial treatment at a single institute between 1993 and 2006. NBCA embolization was considered the primary treatment of choice, with surgery reserved for patients in whom endovascular treatment failed.
Surgery was performed as the primary treatment in one patient because the anterior spinal artery originated from the same arterial pedicle as the artery feeding the fistula. Embolization was used as the primary treatment modality in 17 patients, with an initial success rate of 82.4%. Two patients with incomplete embolization had to undergo surgery. One patient underwent multiple embolizations, which failed to completely occlude the fistula but relieved the patient's symptoms. Spinal DAVF recurred in two patients (one collateral development and one recanalization) during the follow-up period. The collateral development was obliterated by repeated embolization, but the patient with recanalization refused further treatment. The overall clinical status improved in 15 patients (83.3%) during the follow-up period.
Endovascular therapy can be successfully used as a primary treatment for the majority of patients with spinal DAVFs. Although it is difficult to perform in some patients, endovascular embolization should be the primary treatment of choice for spinal DAVF.
PMCID: PMC2615139  PMID: 19137080
Spine; Dural arteriovenous fistula; Therapeutic embolization
16.  Post-Laminectomy Kyphosis in Patients with Cervical Ossification of the Posterior Longitudinal Ligament : Does It Cause Neurological Deterioration? 
Total laminectomy (TL) is an effective surgical technique for the treatment of cervical ossification of the posterior longitudinal ligament (OPLL) along multiple levels. However, kyphosis and probable neurological deterioration have been frequently reported after laminectomy. We analyzed the changes in the cervical curvature after TL and subsequent changes in neurological status.
We retrospectively reviewed the records of 14 patients who underwent TL for the treatment of cervical OPLL between Jan. 1998 and Dec. 2003. TL was selected according to the previously determined criteria. The curvature of the cervical spine was visualized on a lateral cervical spine X-ray and measured using Ishihara's Curvature Index (CI) before the operation and at the last follow-up examination. Perioperative neurological status was estimated using the modified Japanese Orthopedic Association score and the Improvement Rate (IR) at the same time as the images were evaluated.
The mean age of the patients was 57 years, the male/female ratio was 10:4, and the mean follow-up period was 41 months. The mean number of OPLL was 4.9, and the mean number of operated levels was also 4.9. The CI decreased after TL (p=0.002), which was indicative of a kyphotic change. However, this kyphotic change showed no correlation with the length of the follow-up period, number of operated levels and preoperative CI. Neurological examination at the last follow-up showed an improved neurological status in all patients (p=0.001). There was no neurological deterioration in any case during the follow-up period. Moreover, there was no correlation between IR and the degree of kyphotic change. Postoperative complications, such as C5 radiculopathy and epidural bleeding, resolved spontaneously without neurological sequelae.
Kyphotic change was observed in all but one patient who underwent TL for the treatment of cervical OPLL. However, we did not find any contributing factors to kyphosis or evidence of postoperative neurological deterioration.
PMCID: PMC2588253  PMID: 19096629
Total laminectomy (TL); Cervical; Ossification of posterior longitudinal ligament (OPLL); Kyphotic change; Neurological status
17.  Surgical Outcome of Spinal Canal Meningiomas 
We report experiences and clinical outcomes of 61 cases with spinal canal meningiomas from January 1970 through January 2005.
Thirty-eight patients were enrolled with follow-up duration of more than one year after surgery. There were 7 male and 31 female patients. The mean age was 52 years (range, 19 to 80 years). All patients underwent microsurgical resection using a posterior approach.
Twenty-nine (79.4%) cases experienced clinical improvement after surgery. The extent of tumor resection at the first operation was Simpson Grade I in 10 patients, Grade II in 17, Grade III in 4, Grade IV in 6, and unknown in one. We did not experience recurrent cases with Simpson grade I, II, or III resection. There were 6 recurrent cases, consisting of 5 cases with an extent of Simpson grade IV and one with an unknown extent. The mean duration of recurrence was 100 months after surgery. Radiation therapy was administered as a surgical adjunct in four patients (10.5%). Two cases were recurrent lesions that could not be completely resected. The other two cases were malignant meningiomas. No immediate postoperative death occurred in the patient group.
We experienced no recurrent cases of intraspinal meningiomas once gross total resection has been achieved, regardless of the control of the dural origin. Surgeons do not have to take the risk of causing complication to the control dural origin after achieving gross total resectioning of spinal canal meningioma.
PMCID: PMC2588213  PMID: 19096560
Spinal canal; Meningioma; Extent of resection; Recurrence; Control; Dural origin

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