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ABSTRACT: Biomechanics.
To compare the hydrostatic strength of suture and nonpenetrating titanium clip repairs of standard spinal durotomies.
Dural tears are a frequent complication of spine surgery and can be associated with significant morbidity. Primary repair of durotomies with suture typically is attempted, but a true watertight closure can be difficult to obtain because of leakage through suture tracts. Nonpenetrating titanium clips have been developed for vascular anastomoses and provide a close apposition of the tissues without the creation of a suture tract.
Twenty-four calf spines were prepared with laminectomies and the spinal cord was evacuated leaving an intact dura. After Foley catheters were inserted from each end and inflated adjacent to a planned dural defect, the basal flow rate was measured and a 1-cm longitudinal durotomy was made with a scalpel. Eight repairs were performed for each material, which included monofilament suture, braided suture, and nonpenetrating titanium clips. The flow rate at 30, 60, and 90 cm of water and the time needed for each closure were measured.
There was no statistically significant difference in the baseline leak rate for all 3 groups. There was no difference in the leakage rate of durotomies repaired with clips and intact specimens at any pressure. Monofilament and braided suture repairs allowed significantly more leakage than both intact and clip-repaired specimens at all pressures. The difference in leak rate increased as the pressure increased. Closing the durotomy with clips took less than half the time of closure with suture.
Nonpenetrating titanium clips provide a durotomy closure with immediate hydrostatic strength similar to intact dura whereas suture repair with either suture was significantly less robust. The use of titanium clips was more rapid than that of suture repair.
Spine 02/2012; 37(9):E535-9. · 2.08 Impact Factor
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ABSTRACT: Dural tears are a frequent complication of spinal surgery and contribute to significant morbidity. Occasionally, dural tears cannot be closed primarily and dural patch grafts must be utilized. No data exist on the comparative immediate hydrostatic strength of various patch materials used alone or with a biological adhesive in a spinal dural tear model. Thus, the authors conducted this study to determine the comparative effectiveness of various patch materials used with and without biological adhesive.
Twenty-four thoracic spines from calves were prepared with laminectomies and spinal cord evacuation, leaving the dura intact. Foley catheters were inflated on either side of a planned dural defect, and baseline hydrostasis was measured using a fluid column at 30, 60, and 90 cm of H(2)O. A standard dural defect (1 × 2 cm) was created, and 8 patches of each material (human fascia lata, Duragen, and Preclude) were sutured in place using 5-0 Prolene hemo-seal running sutures. Hydrostasis was again tested at the same pressures. Finally, a hydrogel sealant (Duraseal) was placed over the defect and hydrostasis was again tested. Results were analyzed with repeated measures ANOVA.
The leakage rate increased significantly at each pressure tested for all conditions. There was no difference in leakage among the 3 patch materials at any of the pressures or for either condition (with or without sealant). All patch materials allowed significantly greater leakage than the intact condition at all pressures. The use of sealant reduced leakage significantly at the 30 and 60 mm Hg pressures to levels similar to the intact condition. At 90 mm Hg, leakage of the sealed construct was greater than at the intact condition but significantly less than without the use of sealant.
All 3 dural patch materials were of similar hydrostatic strength and allowed greater leakage than at the intact condition. The use of sealant reduced the amount of leakage at all pressures compared with patching alone but allowed more leakage than the intact state at a high hydrostatic pressure (90 mm Hg).
Journal of neurosurgery. Spine 06/2011; 15(4):422-7. · 1.61 Impact Factor
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ABSTRACT: Biomechanical study.
To determine biomechanical forces exerted on intermediate and adjacent segments after two- or three-level fusion for treatment of noncontiguous levels.
Increased motion adjacent to fused spinal segments is postulated to be a driving force in adjacent segment degeneration. Occasionally, a patient requires treatment of noncontiguous levels on either side of a normal level. The biomechanical forces exerted on the intermediate and adjacent levels are unknown.
Seven intact human cadaveric cervical spines (C3-T1) were mounted in a custom seven-axis spine simulator equipped with a follower load apparatus and OptoTRAK three-dimensional tracking system. Each intact specimen underwent five cycles each of flexion/extension, lateral bending, and axial rotation under a ± 1.5 Nm moment and a 100-Nm axial follower load. Applied torque and motion data in each axis of motion and level were recorded. Testing was repeated under the same parameters after C4-C5 and C6-C7 diskectomies were performed and fused with rigid cervical plates and interbody spacers and again after a three-level fusion from C4 to C7.
Range of motion was modestly increased (35%) in the intermediate and adjacent levels in the skip fusion construct. A significant or nearly significant difference was reached in seven of nine moments. With the three-level fusion construct, motion at the infra- and supra-adjacent levels was significantly or nearly significantly increased in all applied moments over the intact and the two-level noncontiguous construct. The magnitude of this change was substantial (72%).
Infra- and supra-adjacent levels experienced a marked increase in strain in all moments with a three-level fusion, whereas the intermediate, supra-, and infra-adjacent segments of a two-level fusion experienced modest strain moments relative to intact. It would be appropriate to consider noncontiguous fusions instead of a three-level fusion when confronted with nonadjacent disease.
Spine 03/2011; 36(6):448-53. · 2.08 Impact Factor
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ABSTRACT: All-terrain vehicles (ATVs) are inherently unstable and their use results in numerous injuries annually in the United States.
We evaluated the magnitude of ATV-related head and spinal column injuries in Utah and identified risk factors that might be addressed by preventative measures.
Four statewide trauma and hospital databases were queried to obtain data on hospital visits by patients with ATV-related neurological injuries in Utah from 2001 to 2005.
Seven hundred forty-one patients (median age, 24 years; range, 2-87 years) with ATV-related head and spinal injuries were identified. Five hundred one patients had injuries requiring transport to a hospital, of which 261 required intensive care. Five hundred fifty-nine patients experienced head trauma and 328 patients sustained spinal trauma. The average injury severity score was 12.6 (range, 0-75). Average hospital stay was 4 days (range, 0-34 days). Vehicle rollover was the most common mechanism of injury (28.6%), followed by loss of control and separation of rider and vehicle (20.1%) and collisions with stationary objects (6.1%) or other vehicles (4.1%). Helmet use was inconsistently documented, but patients without helmets were more likely to have a head injury. Injury frequency increased over time, from 116 in 2001 to 174 in 2005.
The number of ATV-related head and spinal injuries is increasing in Utah. Serious injuries requiring surgery or intensive care are common. Riders under 20 years of age are especially at risk, and helmet use may decrease the likelihood of admission to the intensive care unit, head injuries, and death.
Neurosurgery 10/2010; 67(4):993-7; discussion 997. · 2.79 Impact Factor
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ABSTRACT: Thoracolumbar corpectomy is a procedure commonly required for the treatment of various pathologies involving the vertebral body. Although the biomechanical stability of anterior reconstruction with plating has been studied, the biomechanical contribution of posterior instrumentation to anterior constructs remains unknown. The purpose of this study was to evaluate biomechanical stability after anterior thoracolumbar corpectomy and reconstruction with varying posterior constructs by measuring bending stiffness for the axes of flexion/extension, lateral bending, and axial rotation.
Seven fresh human cadaveric thoracolumbar spine specimens were tested intact and after L-1 corpectomy and strut grafting with 4 different fixation techniques: anterior plating with bilateral, ipsilateral, contralateral, or no posterior pedicle screw fixation. Bending stiffness was measured under pure moments of +/- 5 Nm in flexion/extension, lateral bending, and axial rotation, while maintaining an axial preload of 100 N with a follower load. Results for each configuration were normalized to the intact condition and were compared using ANOVA.
Spinal constructs with anterior-posterior spinal reconstruction and bilateral posterior pedicle screws were significantly stiffer in flexion/extension than intact spines or spines with anterior plating alone. Anterior plating without pedicle screw fixation was no different from the intact spine in flexion/extension and lateral bending. All constructs had reduced stiffness in axial rotation compared with intact spines.
The addition of bilateral posterior instrumentation provided significantly greater stability at the thoracolumbar junction after total corpectomy than anterior plating and should be considered in cases in which anterior column reconstruction alone may be insufficient. In cases precluding bilateral posterior fixation, unilateral posterior instrumentation may provide some additional stability.
Journal of neurosurgery. Spine 08/2010; 13(2):234-9. · 1.61 Impact Factor
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ABSTRACT: Transarticular screw (TAS) fixation is our preferred method for stable internal fixation of the atlantoaxial joint because of its excellent outcomes, versatility, and cost-effectiveness.
In this article, we update our series of patients who have undergone TAS fixation, with attention to surgical technique, planning, complication avoidance, and anatomic suitability.
We retrospectively reviewed 269 patients (150 women, 119 men; average age, 52.9 years; age range, 17-90 years) who underwent placement of at least 1 TAS. In total, 491 TASs were placed for stabilization necessitated by various pathologic conditions. The mean follow-up period was 15.7 months (range, 0-106 months).
Fusion was achieved in 99% of 198 patients monitored until fusion or nonunion requiring revision, or for 2 years. Forty-five patients had a complication, for a rate of 16.7%. Five early patients had vertebral artery injuries, 1 of which was bilateral and fatal. No recent patients had vertebral artery injuries. Other complications did not result in neurologic morbidity. Review of all atlantoaxial fusions by the senior author (R.I.A.) revealed that the TAS fixation technique could be successfully applied in 86.7% of sides considered. The main reasons for inapplicability were anatomic (recognized on preoperative planning) in 77% and abandonment secondary to concern about possible vertebral artery injury on the first side attempted in 13.8%.
The placement of TASs is safe and effective for stabilizing the atlantoaxial articulation. Refinements in technique, such as 3-dimensional stereotactic workstation for trajectory planning, have reduced the rate of serious complications. Clinical outcomes are excellent, with nearly 100% of patients achieving stable bony union.
Neurosurgery 03/2010; 66(3 Suppl):184-92. · 2.79 Impact Factor
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ABSTRACT: Fractures of the odontoid process are the most common fractures of the cervical spine in patients over the age of 70 years. The incidence of fracture nonunion in this population has been estimated to be 20-fold greater than that in patients under the age of 50 years if surgical stabilization is not used. Anterior and posterior approaches have both been advocated, with excellent results reported, but surgeons should understand the drawbacks of the various techniques before employing them in clinical practice.
A retrospective review was undertaken to identify patients who had direct fixation of an odontoid fracture at a single institution from 1991 to 2006. Patients were followed up using flexion-extension radiographs, and stability was evaluated as bone union, fibrous union, or nonunion. Patients with bone or fibrous union were classified as stable. In addition, the incidence of procedure- and nonprocedure-related complications was extracted from the medical record.
Of the 57 patients over age 70 who underwent placement of an odontoid screw, 42 underwent follow-up from 3 to 62 months (mean 15 months). Stability was confirmed in 81% of these patients. In patients with fixation using 2 screws, 96% demonstrated stability on radiographs at final follow-up. Only 56% of patients with fixation using a single screw demonstrated stability on radiographs. In the immediate postoperative period, 25% of patients required a feeding tube and 19% had aspiration pneumonia that required antibiotic treatment.
Direct fixation of Type II odontoid fractures showed stability rates > 80% in this challenging population. Significantly higher stabilization rates were achieved when 2 screws were placed. The anterior approach was associated with a relatively high dysphagia rate, and patients must be counseled about this risk before surgery.
Journal of neurosurgery. Spine 01/2010; 12(1):1-8. · 1.61 Impact Factor
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ABSTRACT: An iliac crest autograft is the gold standard for bone grafting in posterior atlantoaxial arthrodesis but can be associated with significant donor-site morbidity. Conversely, an allograft has historically performed suboptimally for atlantoaxial arthrodesis as an onlay graft. The authors have modified a bone grafting technique to allow placement of a bicortical iliac crest allograft in an interpositional manner, and they evaluated it as an alternative to an autograft in posterior atlantoaxial arthrodesis.
The records of 89 consecutive patients in whom C1-2 arthrodesis was performed between 2001 and 2005 were reviewed.
Forty-seven patients underwent 48 atlantoaxial arthrodeses with an allograft (mean follow-up 16.1 months, range 0-49 months), and 42 patients underwent autograft bone grafting (mean follow-up 17.6 months, range 0-61.0 months). The operative time was 50 minutes shorter in the allograft (mean 184 minutes, range 106-328 minutes) than in the autograft procedure (mean 234 minutes, range 154-358 minutes), and the estimated blood loss was 50% lower in the allograft group than in the autograft group (mean 103 ml [range 30-200 ml] vs mean 206 ml [range 50-400 ml], respectively). Bone incorporation was initially slower in the allograft than in the autograft group but equalized by 12 months postprocedure. The respective fusion rates after 24 months were 96.7 and 88.9% for autografts and allografts. Complications at the donor site occurred in 16.7% of the autograft patients, including 1 pelvic fracture, 1 retained sponge, 1 infection, 2 hernias requiring repair, 2 hematomas, and persistent pain.
The authors describe a technique for interpositional bone grafting between C-1 and C-2 that allows for the use of an allograft with excellent fusion results. This technique reduced the operative time and blood loss and eliminated donor-site morbidity.
Journal of neurosurgery. Spine 10/2009; 11(4):396-401. · 1.61 Impact Factor
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ABSTRACT: In severe cases, posttraumatic cerebral sinus thrombosis can result in venous congestion and persistent intracranial hypertension refractory to both conventional medical therapy and surgical decompression. The authors report a unique case of a patient successfully treated with endovascular mechanical thrombolysis using balloon angioplasty for clinically significant posttraumatic venous sinus thrombosis and review the reported treatments for cerebral venous sinus occlusive disease. This 18-year-old man suffered severe closed head injury from a fall while skateboarding. A head CT scan demonstrated basilar skull fractures involving the left jugular foramen. A CT angiogram revealed thrombosis of the left transverse sinus and occlusion of the sigmoid sinus and internal jugular vein. Despite treatment with anticoagulation therapy and decompressive hemi- and suboccipital craniectomies, intracranial hypertension remained refractory. Serial angiography demonstrated progressive sinus occlusion. Endovascular balloon thrombolysis of the left transverse and sigmoid sinuses resulted in immediate reduction of intracranial pressures and improved sinus patency. Intracranial pressure measurements remained low after the procedure. The patient eventually improved neurologically, was able to follow commands and walk, and was discharged to a rehabilitation facility for further recovery. Anticoagulation therapy, surgical decompression, and endovascular thrombolysis have been reported as treatment modalities for clinically significant posttraumatic venous sinus thrombosis. In this case, endovascular mechanical thrombolysis with balloon angioplasty resulted in resolution of thrombus and successful immediate reduction of intracranial pressure. This treatment may be considered in patients with critically elevated intracranial pressure from posttraumatic venous sinus occlusion refractory to other treatment measures.
Journal of Neurosurgery 04/2009; 111(1):17-21. · 2.96 Impact Factor
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ABSTRACT: Instability of the occipitocervical junction can be a challenging surgical problem because of the unique anatomic and biomechanical characteristics of this region. We review the causes of instability and the development of surgical techniques to stabilize the occipitocervical junction.
Occipitocervical instrumentation has advanced significantly, and modern modular screw-based constructs allow for rigid short-segment fixation of unstable elements while providing the stability needed to achieve successful fusion in nearly 100% of patients. This article reviews the preoperative planning, the variety of instrumentation and surgical strategies, as well as the postoperative care of these patients.
Current constructs use occipital plates that are rigidly fixed to the thick midline keel of the occipital bone, polyaxial screws that can be placed in many different trajectories, and rods that are bent to approximate the acute occipitocervical angle. These modular constructs provide a variety of methods to achieve fixation in the atlantoaxial complex, including transarticular screws or C1 lateral mass screws in combination with C2 pars, C2 pedicle, or C2 translaminar trajectories.
Surgical techniques for occipitocervical instrumentation and fusion are technically challenging and require meticulous preoperative planning and a thorough understanding of the regional anatomy, instrumentation, and constructs. Modern screw-based techniques for occipitocervical fusion have established clinical success and demonstrated biomechanical stability, with fusion rates approaching 100%.
Neurosurgery 12/2008; 63(5):961-8; discussion 968-9. · 2.79 Impact Factor
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ABSTRACT: Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link.
Ten intact human cadaveric spines (Oc-C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested.
All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct.
All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.
Journal of Neurosurgery Spine 10/2008; 9(3):296-300. · 1.53 Impact Factor
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ABSTRACT: Metastatic tumor in the spinal column is common, causing symptomatic spinal cord compression in approximately 25,000 patients annually. Although surgical treatment of spinal metastases has become safer, less invasive, and more efficacious in recent years, there remains a subset of patients for whom other treatment modalities are needed. Stereotactic radiosurgery, which has long been used in the treatment of intracranial lesions, has recently been applied to the spine and enables the effective treatment of metastatic lesions.
We review the evolution of stereotactic radiosurgery and its applications in the spine, including a description of two commercially available systems.
Although a relatively new technique, the use of stereotactic radiosurgery in the spine has advanced rapidly in the past decade. Spinal stereotactic radiosurgery is an effective and safe modality for the treatment of spinal metastatic disease.
Future challenges involve the refinement of noninvasive fiducial tracking systems and the discernment of optimal doses needed to treat various lesions. Additionally, dose-tolerance limits of normal structures need to be further developed. Increased experience will likely make stereotactic radiosurgery of the spine an important treatment modality for a variety of metastatic lesions.
Cancer control: journal of the Moffitt Cancer Center 11/2007; 14(4):405-11.
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ABSTRACT: Pigmented villonodular synovitis (PVNS) is a proliferative disorder of the synovium with a predisposition for the appendicular skeleton. Rarely PVNS can arise from the spine, where this disorder usually presents with localized or radicular pain secondary to involvement of the posterior elements. The authors report the case of an 82-year-old woman who presented with long-standing neck pain and acute upper-extremity numbness and weakness. Computed tomography imaging revealed a mixed sclerotic and lucent lesion affecting the dens and right lateral mass of C-2. There was also a pathological fracture at the base of the dens with 8 mm of anterior dens displacement. Magnetic resonance imaging demonstrated a diffusely infiltrative process that was nonenhancing. Because of instability, the patient underwent transarticular screw fixation, and a biopsy of the lesion was also performed at this time. Histopathological analysis was consistent with a diagnosis of PVNS. To the authors' knowledge, this is the first report of PVNS involving the C-2 vertebra or causing a pathological fracture.
Journal of Neurosurgery Spine 09/2007; 7(2):248-53. · 1.53 Impact Factor
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ABSTRACT: Castleman disease is a rare lymphoproliferative disease of unknown cause. In most cases, afflicted patients present with a mediastinal mass although the disease may manifest in numerous other sites, including intracranially and rarely intraspinally. The authors report on the case of a 19-year-old woman who presented with a large paraspinal mass emanating from the T7-8 neural foramen. The morphological and signal characteristics revealed on magnetic resonance imaging were similar to those of nerve sheath tumors. The patient underwent open biopsy sampling of the lesion, and results of a pathological evaluation revealed hyaline-vascular type Castleman disease. She underwent radiotherapy and remains symptom-free with a radiographically stable lesion 1 year later. Although the disease has been reported to mimic a meningioma when encountered in intracranial locations, to the authors' knowledge, this is the first case of the disorder mimicking a nerve sheath tumor. When the diagnosis of Castleman disease is made, good results can be obtained with partial resection and radiotherapy.
Journal of Neurosurgery Spine 06/2007; 6(5):455-9. · 1.53 Impact Factor
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ABSTRACT: Transient postictal imaging abnormalities in patients with non-tumor-related seizures are well documented and include fluid-attenuated inversion recovery/T2 hyperintensity and parenchymal and meningeal contrast enhancement. In contrast, transient postictal imaging abnormalities in patients with tumor-related seizures have been poorly described. Fifty percent of patients with brain tumors have a seizure during the course of their illness and are often imaged after a seizure or after a change in seizure character or frequency. Interval changes on repeat imaging can mimic disease progression or other pathologic processes.
We describe 3 patients with brain tumors and transient postictal MRI changes that mimicked disease progression and infection.
Our patients demonstrated fluid-attenuated inversion recovery/T2 hyperintensity and gadolinium enhancement on MRI studies performed shortly after ictal events. These changes were suspicious for tumor progression in 2 cases and for recurrent infection in the third. Control of seizure activity resulted in resolution of these changes on scans obtained 10 to 21 days later.
Imaging shortly after an ictal event can potentially mislead the clinician to interpret changes as tumor or pathologic progression. Unnecessary intervention in these patients with new and suspicious imaging findings should be avoided. We recommend repeat imaging be performed in patients with brain tumors and seizures several weeks after seizure control if clinically feasible. Further research is needed to delineate the time course of seizure-induced MRI changes.
Surgical Neurology 04/2007; 67(3):246-50; discussion 250. · 1.67 Impact Factor
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ABSTRACT: Spinal lipomas, particularly lipomas of the conus medullaris and terminal filum, are the most common form of occult spinal dysraphism and represent a wide spectrum of disease with regard to anatomy, clinical presentation, and treatment options. These lesions, however, are united by a similar embryology and pathological mechanism by which symptoms arise. Recently, the treatment of these lesions has generated much controversy, with some physicians advocating surgical treatment for all patients regardless of symptoms and others proposing that surgery be withheld until symptoms develop. The authors discuss lumbosacral spinal lipomas, with particular attention to the theories of their origin, anatomical and pathological features, and treatment options, including a review of current controversies.
Neurosurgical FOCUS 02/2007; 23(2):E10. · 2.87 Impact Factor
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ABSTRACT: Castleman disease is a rare lymphoproliferative disease of unknown cause. In most cases, afflicted patients present with a mediastinal mass although the disease may manifest in numerous other sites, including intracranially and rarely intraspinally. The authors report on the case of a 19-year-old woman who presented with a large paraspinal mass emanating from the T7–8 neural foramen. The morphological and signal characteristics revealed on magnetic resonance imaging were similar to those of nerve sheath tumors. The patient underwent open biopsy sampling of the lesion, and results of a pathological evaluation revealed hyaline-vascular type Castleman disease. She underwent radiotherapy and remains symptom-free with a radiographically stable lesion 1 year later. Although the disease has been reported to mimic a meningioma when encountered in intracranial locations, to the authors’ knowledge, this is the first case of the disorder mimicking a nerve sheath tumor. When the diagnosis of Castleman disease is made, good results can be obtained with partial resection and radiotherapy.
