Intradural Spinal Cord Research Articles

Soft-coupling suspension system for an intradural spinal cord stimulator: Biophysical performance characteristics

We have characterized the mechanical compliance of an improved version of the suspension system used to position the electrode-bearing membrane of an intradural neuromodulator on the dorsal pial surface of the spinal cord. Over the compression span of 5 mm, it exhibited a restoring force of 2.4 μN μm−1 and a mean pressure of 0.5 mm Hg (=66 Pa) on the surface below it, well within the range of normal intrathecal pressures. We have implanted prototype devices employing this suspension and a novel device fixation technique in a chronic ovine model of spinal cord stimulation and found that it maintains stable contact at the electrode-pia interface without lead fracture, as determined by measurement of the inter-contact impedances.

MR-based measurement of spinal cord motion during flexion of the spine: implications for intradural spinal cord stimulator systems

This study develops a means of delivering electrical stimuli directly to the pial surface of the spinal cord for treatment of intractable pain. This intradural implant must remain in direct contact with the cord as it moves within the spinal canal. Therefore, magnetic resonance imaging was used to measure the movement of the spinal cord between neutral and flexed-back positions in a series of volunteers (n = 16). Following flexion of the back, the mean change in the pedicle-to-spinal cord dorsal root entry zone distance at the T10-11 level was (8.5 ± 6.0) mm, i.e. a 71% variation in the range of rostral-caudal movement of the spinal cord across all patients. There will be a large spectrum of spinal cord strains associated with this observed range of rostral-caudal motions, thus calling for suitable axial compliance within the electrode bearing portion of the intradural implant.

Dynamic loading characteristics of an intradural spinal cord stimulator

We have measured the forces that act on the electrode-bearing surface of an intradural neuromodulator designed to be in direct contact with the pial surface of the spinal cord, as part of our effort to develop a new method for treating intractable pain. The goal was to investigate the pressures produced by this device on the spinal cord and compare them with normal intrathecal pressure. For this purpose, we employed a dual-sensor arrangement that allowed us to measure the response of a custom-designed silicone spinal cord surrogate to the forces applied by the device. We found that the device had a mean compliance of ≈63 μN μm−1, and that over a 3 mm range of compression, the mid-span pressure it exerted on the spinal cord was ≈1.88 × 103 Pa = 14.1 mm Hg, which lies within the range of normal intrathecal pressure in humans.

Granular Cell Tumor of the Intradural Extramedullary Spinal Cord : Report of Two Cases with Respect to Radiological Differential Diagnosis

Granular cell tumors (GrCTs) of the spinal cord are rare benign tumors with a high rate of local recurrence. Only 6 cases of spinal GrCTs have been reported. GrCT is difficult to distinguish from other benign tumors such as schwannoma using imaging. A radiological "speckled dots" sign may be a useful differentiating feature of GrCT based upon experience with two cases and a review of the literature.

Optimization of Intradural Spinal Cord Stimulator Designs via Analysis of Thoracic Spine Imaging Data

Axial magnetic resonance images of the thoracic spinal cord of 50 patients are analyzed in order to measure the length of the dorsal arc span between the dorsal root entry zones for the purpose of optimizing the mechanical design dimensions of the Human Spinal Cord Modulation System (HSCMS), which delivers electrical stimuli directly to the spinal cord. Two mathematical approaches are used to assess the data, with validation of the results conducted via a direct physical measurement using a magnified image. Results show that the nominal value of the arc length is 6.7 ± 1.0 mm (1 σ), with high and low values of 8.8 and 5.1 mm, respectively. The mean radius of the spinal cord was found to be 3.6 ± 0.5 mm. Taking into account previously reported measurements, it is suggested that values at the high end of this range be used for further morphometric studies of the cord in the thoracic region. The implications of these findings on the design of the HSCMS are discussed.

Ultrasonic BoneScalpel for Osteoplastic Laminoplasty in the Resection of Intradural Spinal Pathology

Osteoplastic laminoplasty is a well-described technique that may decrease the incidence of progressive kyphosis when used in the setting of intradural spinal cord tumor resection. The BoneScalpel by Aesculap (Central Valley, Pennsylvania) is an ultrasonic osteotome that precisely cuts bone while preserving the underlying soft tissues, potentially reducing the risk of dural laceration during laminoplasty. By producing osteotomies as narrow as 0.5 mm, the device may also facilitate postoperative osteointegration. A retrospective analysis was conducted of 40 patients (mean age, 38.0 years; range, 4.0-79.7 years) who underwent osteoplastic laminoplasty using the BoneScalpel for the treatment of intradural spinal pathology at the Johns Hopkins Hospital between January 2009 and December 2011. After lesion resection, titanium plates were used to reconstruct the lamina in all cases. The technical results and procedure-related complications were subsequently noted. Successful laminoplasty was carried out in all 40 patients. Intraoperatively, 1 case of incidental durotomy was noted after use of the device, which was repaired primarily without neurological or clinical sequelae. During the follow-up period (mean, 195 days; median, 144 days), there were 2 complications (1 cerebrospinal fluid leak, 1 seroma) and no cases of immediate postoperative instability. The BoneScalpel is a safe and technically feasible device for performing osteoplastic laminoplasty.

Ovine Tests of a Novel Spinal Cord Neuromodulator and Dentate Ligament Fixation Method

ABSTRACTBackground: To improve methods for the treatment of intractable pain, we are developing a novel intradural spinal cord stimulator that could be either attached to the dentate ligaments of the human spinal cord or fitted around the dorsal arc of the cord itself. Purpose: Our goal was to carry out the first in vivo tests of these attachment methods in an ovine model using custom-built devices and instrumentation. For eventual translational studies, we also explored methods of mimicking a human dentate ligament attachment technique in this large animal model. Methods: As a starting point, we investigated details of the gross and histological anatomy of the ovine denticulate ligaments, and compared them with their human counterpart. The gap between the dura and the spinal cord in the sheep is small; hence, the denticulate ligaments are not long enough to accommodate human-scaled attachment clips. Therefore, lateral strips of the spinal-canal dura were fashioned to serve this same device attachment function. Results: This form of dural anchoring was implemented surgically for fixation of a silicone membrane implant that had 12 electrodes, and somatosensory evoked potentials were obtained successfully when stimuli were applied to it. The dorsal arc clamping technique was also implemented. Conclusions: We demonstrated that the dural attachment method is an effective surrogate model for testing the human dentate ligament device fixation technique, and that this mode of fixation was preferable to dorsal arc attachment. The relevant surgical innovations, anatomical findings, and the preliminary electrophysiological data from a pial surface stimulator attached in this way are presented.

Is closed-suction drainage necessary after intradural primary spinal cord tumor surgery?

The efficacy of closed-suction drainage in primary intradural spinal cord tumor surgery has not been addressed. We investigated whether closed-suction drainage is essential after primary intradural spinal cord tumor surgery. From January 2003 to October 2011, 169 consecutive patients with primary intradural spinal cord tumors operated by a single surgeon were selected. Closed-suction drainage was inserted in patients before August 2007, but was not used after August 2007. After removal of tumor and meticulous hemostasis, the opened dura was closed and made watertight using 4-0 silk with interrupt suture and 1.0cm(3) of surgical glue was applied in common. Closed-suction drainage was inserted below the muscular fascia in 75 patients (group I, M:F=39:36; 46.20±15.63years) and was not inserted in 94 patients (group II, M:F=46:48; 51.05±14.89years). Neurological deficit precluding ambulation did not occur in all patients. Between group I and II, there were no significant differences in body mass index (22.75±3.16 vs. 23.51±3.22kg/m(2); p=0.13), laminectomy level (2.45±1.46 vs. 2.33±1.91; p=0.65), operation time (260.65±109.08 vs. 231.52±90.08min; p=0.06), estimated intraoperative blood loss (456.93±406.62 vs. 383.94±257.25cm(3); p=0.18), and hospital stay period (9.25±5.01 vs. 9.35±5.75days; p=0.91). Two patients in group I underwent revision surgery due to wound problems, while revision surgery was not performed in group II (p=0.20). Closed-suction drainage may not be essential after primary intradural spinal cord tumor surgery.

Spinal canal surrogate for testing intradural implants

We have designed, built and tested an anthropomorphic-scale surrogate spinal canal, for use in preliminary evaluations of the performance characteristics of a novel intradural spinal cord stimulator. The surrogate employs a silicone mock spinal cord with semi-major and semi-minor diameters of 10 and 6 mm, respectively, commensurate with those of actual thoracic-level spinal cord. The axial restoring force provided by the 300 µm thick silicone denticulate ligament constructs on the mock cord is ~ 0.32 N mm−1 over a 1.5 mm range of displacement, which is within a factor of 2 of that measured by others in human cadaver specimens. Examples of testing protocols of prototype intradural stimulators that employ this device are discussed.

Is Closed-Suction Drainage Necessary for Intradural Primary Spinal Cord Tumor Surgery?

Is Closed-Suction Drainage Necessary for Intradural Primary Spinal Cord Tumor Surgery?

Cervical ependymoma resection.

Intradural intramedullary cervical spinal cord tumors pose a significant challenge for the neurosurgeon to resect with minimal morbidity. We present the case of a 12-year-old male with a cervical ependymoma and demonstrate our resection technique. The video can be found here: http://youtu.be/5DHlnxdggU0 .

Intraspinal Penetrating Stab Injury to the Middle Thoracic Spinal Cord With No Neurologic Deficit

The annual incidence of traumatic spinal cord injury worldwide is estimated to be 35 patients per million. Nonmissile penetrating spinal injuries most commonly occur in the thoracic region, and the majority has neurologic deficits on admission. The management of patients who lack neurologic deficits is controversial due to the risk of neurologic status alteration intraoperatively. However, failure to intervene increases the risk of infection, delayed onset of neurologic deficits, and worsening functional outcome.A 17-year-old boy presented with an intradural T7-T8 knife penetration injury to the spinal cord with no neurologic deficit. Rapid surgical intervention was critical because the knife was lodged between the 2 hemispheres of the spinal cord. The patient was intubated in the lateral position, transferred to the prone position on a Jackson table, and underwent surgical decompression with laminectomy 1 level above and below the injury site, removal of the knife blade in the original path of trajectory, and repair of the dural tear with a collagen matrix. The patient sustained no neurologic sequelae from the penetrating knife injury. He was able to ambulate at discharge and had no complications. To our knowledge, this is the only report of a patient with intradural spinal cord penetration by a foreign object (knife blade) presenting with a normal neurologic preoperative examination that persisted throughout the course of postoperative care.

Applier tool for intradural spinal cord implants

We have designed, built and tested a novel device for placing intradural neurmodulator implants directly on the pial surface of the spinal cord. This applier tool is designed for ergonomic handling of delicate electro-mechanical devices such as the Iowa-Patch™ spinal cord stimulator implant, which is aimed at overcoming certain shortcomings in the performance of standard epidural stimulator devices. The applier is approximately 14 cm long, 6 mm in diameter, made of stainless steel components, and has simple and reliable mechanisms for the attachment and release of the implant from it. We describe the design of the device, details of its construction, and its performance during in vivo testing of somatosensory evoked potentials in an ovine model of intradural spinal cord stimulation.

Intradural Extramedullary and Subcutaneous Tumors in Neonate : Atypical Myxoid Spindle Cell Neoplasm

Tumors of the central nervous system are common in the pediatric population and constitute the second most prevalent tumor type in children. Within this group, spinal cord tumors are relatively rare and account for 1 to 10% of all pediatric central nervous system tumors. We describe a very rare case of an intradural extramedullary spinal cord tumor with a subcutaneous mass and discuss its clinical presentation, pathogenesis, and treatment. A male infant was delivered normally, with uneventful development. At 16 days post-delivery, his family took him to a pediatrician because of a mass on his upper back. Magnetic resonance imaging of the thoracic spine revealed a well-demarcated soft-tissue mass with central cystic change or necrosis at the subcutaneous layer of the posterior back (T2-7 level). Another mass was found with a fat component at the spinal canal of the T1-3 level, which was intradural extramedullary space. After six weeks, the spinal cord tumor and subcutaneous mass were grossly total resected; pathologic findings indicated an atypical myxoid spindle cell neoplasm, possibly nerve sheath in type. The final diagnosis of the mass was an atypical myxoid spindle cell neoplasm. The postoperative course was uneventful, and the patient was discharged after nine days without any neurological deficit. We report a rare case of an intradural extramedullary spinal tumor with subcutaneous mass in a neonate. It is necessary to monitor the patient's status by examining consecutive radiologic images, and the symptoms and neurological changes should be observed strictly during long-term follow-up.

Delay in diagnosis of primary intradural spinal cord tumors

Background:It has been our impression in recent years that there is a significant delay in diagnosis (DID) of patients in Israel harboring intradural spinal cord tumors (IDSCTs). DID can lead to irreversible deficits and unnecessary suffering. Our goal was to identify the incidence and the specific reasons for DID of IDSCTs in patients operated upon at our institution.Methods:A retrospective record review, with additional telephone survey, of 101 patients operated upon at our institute between the years 1996 and 2009 was conducted. The patients who were not diagnosed locally and those who were diagnosed during routine spinal imaging studies as part of their basic disease check-up were excluded. Accordingly, neurofibromatosis and medical tourist patients were excluded.Results:The clinical presentation of IDSCTs in our study was similar to the descriptions given in previous reports. The average age was 41.9 ± 23.3 years. Most tumors were ependymomas, astrocytomas, and schwannomas. The most common symptoms were motor or sensory disturbance, back pain, walking disturbance, and sphincter control deficit. The median time to diagnosis was 12.0 ± 37.0 months (range 3 days to 20 years). We found DID in 82.2% of the cases. 62.4% of the cases were defined as “unreasonable delay.” The most common reasons for DID were “classical symptoms with a wrong diagnosis” and “delayed imaging.”Conclusions:Based on the results of this study, the incidence of unreasonable delays in diagnosis of primary IDSCTs in Israel is very high. In order to shorten the time to diagnosis, primary and secondary care physicians need to increase their awareness of symptoms that may be associated with these lesions. We hereby offer feedback for care providers, relevant to the diagnostic workup of these patients. Such a feedback must be delivered by neurosurgeons to the community they are serving.

Minimally Invasive Removal of an Intradural Cervical Tumor : Assessment of a Combined Split-Spinous Laminectomy and Quadrant Tube Retractor System Technique

Conventional laminectomy is the most popular technique for the complete removal of intradural spinal tumors. In particular, the central portion intramedullary tumor and large intradural extramedullary tumor often require a total laminectomy for the midline myelotomy, sufficient decompression, and adequate visualization. However, this technique has the disadvantages of a wide incision, extensive periosteal muscle dissection, and bony structural injury. Recently, split-spinous laminectomy and tubular retractor systems were found to decrease postoperative muscle injuries, skin incision size and discomfort. The combined technique of split-spinous laminectomy, using a quadrant tube retractor system allows for an excellent exposure of the tumor with minimal trauma of the surrounding tissue. We propose that this technique offers possible advantages over the traditional open tumor removal of the intradural spinal cord tumors, which covers one or two cervical levels and requires a total laminectomy.

Intradural Spinal Cord Tumor Resections by a Neurosurgeon at a Tertiary Care Hospital

Introduction: Intradural spinal cord tumors are rare. A retrospective analysis was conducted on patients who underwent surgical resection of an intradural spinal cord tumor between 9/4/1998 and 10/1/2010 by one surgeon. Methods: Cases included adults (>18 years old) who had undergone spinal tumor resections. Endpoints examined included complication rates, discharge destinations, and lengths of hospitalization. Data was obtained via chart abstraction. Contingency tables were created, and estimates of relative risk (RR) with 95% confidence intervals (CIs) were calculated to determine the relationship between the endpoints of interest and a variety of variables (e.g., sex, ethnicity, tumor location). Sixty-six cases met the inclusion criteria. Results: The median lengths of stay for males and females were 4 and 5 days, respectively; the distributions in the two groups differed significantly (Mann-Whitney U=541.5, nmale=30, nfemale=36, P

Is intraoperative ultrasound required in cervical spinal tumors ? a prospective study

To determine the role of intraoperative ultrasonography (IOUSG) in the surgical management of patients with intradural spinal tumors. Twenty-six patients with intradural spinal cord tumors were surgically treated under intraoperative ultrasonographic guidance between January 2007 and May 2011. Guidance with IOUSG was used in 26 patients, of which 14 fourteen had extramedullary and 12 had intramedullary tumors. Intraoperative ultrasound assistance was used to localize each tumor exactly before opening the dura. The extent of tumor resection was verified using axial and sagittal sonographic views. The extent of tumor resection achieved with IOUSG guidance was assessed on postoperative early control MRI sections. Total tumor resection was achieved in 22 (84%) of 26 cases. All of the residual tumors were typically intramedullary and infiltrative. The sensitivity of IOUSG for the determination of the extent of resection was found to be 92%. Ultrasonography was found to be effective in identification of tumor boundaries and protection of spinal cord vessels. The average time spent for IOUSG assessment was 7 minutes. Intraoperative ultrasonography is practical, reliable and highly sensitive for spinal cord surgery. It not only enhances surgical orientation, but also reduces morbidity and helps to resect the tumor completely.

Clinical presentation and outcome of patients with intradural spinal cord tumours

We aimed to retrospectively investigate the clinical presentation and outcome of surgical intervention of patients with intradural spinal cord tumours (IDSCT), and to assess the predictors of surgical outcome. A total of 109 patients with IDSCT (57 males and 52 females) (130 admissions; mean age, 45.9 years; range, 14–89 years) underwent surgery between 1 January 1994 and 30 June 2009 at The Royal Melbourne Hospital. Ninety per cent of tumours were classified as low grade. Pain was the most common symptom at presentation (60%) and the mean duration of symptoms was 37.8 weeks (0–4 years). Total resection was achieved in 72.3% of patients with IDSCT. An extramedullary location was the strongest predictor of greater extent of tumour resection (odds ratio [OR] = 4.367, 95% confidence interval [CI] = 1.876–10.204, p = 0.001), whereas a rostral location was also a significant predictor of greater resection (OR = 1.393, 95% CI = 1.014–1.908, p = 0.040). The surgical mortality rate was 0.92%. A good pre-operative clinical grade was the strongest predictor of a positive post-operative neurological status at discharge for IDSCT (OR = 7.382, 95% CI = 4.575–11.912, p < 0.001). The mean follow-up was 37.9 months (16 days–165 months). A good post-operative clinical grade was the most significant predictor of a positive neurological outcome at short-term follow-up (OR = 9.953, 95% CI = 4.941–20.051, p < 0.001), while a good pre-morbid clinical grade was the most significant predictor of a positive outcome at long-term follow-up (OR = 9.498, 95% CI = 2.780–32.451, p < 0.001). We concluded that surgical outcome was influenced by pre-morbid, pre-operative and post-operative clinical grades, the extent of resection, tumour grade and tumour location with respect to the spinal parenchyma. Surgical intervention has a high success rate for tumour control and we recommend total resection where possible.

Surgical Outcome of a Posterior Approach for Large Ventral Intradural Extramedullary Spinal Cord Tumors

Case series. The object of this study is to present surgical outcomes for treatment of large ventral intradural extramedullary (IDEM) spinal cord tumors with conventional laminectomy. Most IDEM spinal cord tumors are meningiomas and schwannomas, which are separated from the spinal cord by a discrete anatomical barrier (the arachnoid or pia membrane). As a result of this anatomical barrier, a tumor can be removed using the posterior approach with conventional laminectomy. Although many reports have demonstrated the feasibility of the posterior approach for ventral tumors, there have been no studies detailing large ventral IDEM tumors. From 2001 to 2008, we operated on 18 consecutive patients with a large ventral IDEM tumor using the posterior approach (8 cervical and 10 thoracic). Preoperatively, eight patients were classified as having Nurick grade 1 myelopathy, six patients had grade 2, and four had grade 3. Tumors were removed through a slit-like space between the dura and spinal cord without retraction of the spinal cord. Complete removal of the tumor was possible in 17 cases. The follow-up period was 39 ± 28 months (range = 10-97 months). There were 7 cases of meningiomas and 11 of schwannomas. One schwannoma was mixed with the cervical rootlets and the mass in the foramen was left behind. Clinical symptoms improved in 16 patients and stabilized in 2. The one residual mass was stable for 62 months. There were no cases of recurrence. Neither kyphotic change nor instability developed in any of the patients during the follow-up period. Large ventral IDEM spinal cord tumors can be completely removed using a posterior approach and conventional laminectomy. An understanding of the anatomical and growth characteristics of these tumors is extremely important for successful removal. However, this approach should be applied prudently and with a thorough understanding of its limitations.