AANS 2007

Abstract: 2007 Apr 18
Dynamic intraspinous Spacer Technology (DIAM) for Posterior Dynamic Stabilization: clinical and radiographic mean 29 month follow-up
Author(s):
Keun-Young A. Kim, MD (Los Angeles, CA)
Matthew McDonald, MD (Adelaide, Australia)
Justin HT Pik, MD (Canberra, Australia)
Alex Taghva, MD
Michael Y. Wang, MD (Los Angeles, CA)

Introduction: We compared outcomes of patients post-microdiscectomy or laminectomy lumbar surgery with dynamic intraspinous spacer technology (DIAM) versus patients who underwent lumbar surgery alone.

Methods: Seventy-four patients underwent simple lumbar surgery (laminectomy and/or microdiscectomy) in a 60-month period. Of these, 35 patients underwent concomitant surgical placement of DIAM interspinous process spacer (a total of 42 DIAMs). Postoperatively, magnetic resonance imaging, upright radiographic imaging, pain scores, and clinical assessment were followed to a mean of 29 months (range 17-60 months). Patients who underwent no interspinous process spacer (Group C) were compared with patients who underwent placement of DIAM (Group D).

Results: In Group D, no statistically significant differences were noted in anterior or posterior disc height when comparing pre- to postoperative patients. When compared with Group C, a relative kyphosis of 3 degrees was noted in Group D postoperative images (Group C: 2.68±0.54 degrees; Group D: -0.51±0.1 degrees). No statistically significant differences in pain Visual Analogue Scale (VAS) or MacNab outcomes were noted at a mean of 29 months follow-up between Groups C and D. Complications in Group D included three intraoperative spinous process fractures, one infection, and one case of markedly increased disc degeneration and facet disease at 2-year follow-up.

Conclusions: Following simple lumbar surgery, placement of a DIAM interspinous process spacer does not alter disc height and sagittal alignment was minimally altered at a mean of 29 months follow-up. No difference in VAS or MacNab outcome was noted between DIAM and non-DIAM groups, particularly in the use of DIAM to alleviate low back pain.

Keywords:
lumbar surgery
posterior dynamic stabilization
DIAM
microdiskectomy

Abstract: 2007 Apr 15
A Lower Admission Glasgow Coma Scale (GCS) Score Corresponds to an Increased Likelihood of Mashall Classification Progression
Author(s):
Jennifer Orning, BS
Alen Nourian, BS
Bill Zhou, MD
Chi S. Zee, MD
Bryan C. Oh, MD
Steven L. Giannotta, MD (Los Angeles, CA)

Introduction: Traumatic subarachnoid hemorrhage (tSAH) is common in patients with head injury. The Marshall classification is becoming used more frequently to grade the severity of tSAH. However, little data exist regarding specific factors that contribute to the development of a higher Marshall score. This study was designed to identify factors that put tSAH patients at risk for developing a higher Marshall score.

Methods: From June to August 2006, 30 patients (22 males (age 46.4 ± 18.9 years) and eight females (age 45.8 ± 26.1 years)) were admitted to LAC+USC Medical Center with an admission diagnosis of tSAH, given an initial Marshall score, and followed prospectively. Other data gathered were initial Glasgow Coma Scale (GCS) score, coagulation status, blood pressure, and toxicology screen. All patients received follow-up head computed tomography (CT) scans for surveillance 12-24 hours after the initial scan or for change in examination. All Marshall scores were assigned by the same neuroradiology staff.

Results: Patients were grouped into one of three categories: 1) improved (or lower) Marshall score; 2) stable score; or 3) worse (or higher) score. The patients who developed a higher Marshall score had a lower initial GCS score (7.1±3.8) compared with patients who had stable a Marshall score (GCS 11.9±4.5). This difference, however, was not statistically significant (P less than 0.06). The patients who developed a higher Marshall score had a significantly lower (P less than 0.01) initial GCS (7.1±3.8) compared with patients who had a lower Marshall score on follow-up imaging (12.0±2.5).

Conclusions: This study suggests that tSAH patients who develop a higher Marshall score tend to present with a significantly lower GCS score.

Keywords:
Traumatic Subarachnoid Hemorrhage
Marshall Classification
Traumatic Brain Injury
Head Trauma

Abstract: 2007 Apr 15
Calvarial Growth Following Surgical Treatment of Craniosynostosis
Author(s):
Alex Khalessi, MD
Mark D. Krieger, MD
Ira Bowen, BA
J. Gordon McComb, MD (Los Angeles, CA)

Introduction: Calvarial growth may represent a viable outcome measure for the surgical treatment of craniosynostosis.

Methods: From 2000 to 2005, 117 children were surgically treated for craniosynostosis at a single institution. Head circumference (HC) measurements were retrospectively reviewed preoperatively, immediately postoperatively (1-2 weeks), and at short-term follow-up (6 months to 1 year). Using population-based HC growth curves, data points were assigned a percentile score. Subjects were classified into three postoperative outcome states: 1) patient HC remained stable on a percentile growth curve, 2) patient HC moved to a lower percentile growth curve, and 3) patient HC moved to a higher growth curve.

Results: Study population descriptive statistics were as follows: mean age 9 months; gender breakdown: 26% female and 74% male; and follow-up from 3 to 56 months (mean 18 months). Subsets included: isolated sagittal synostosis (ISS) (59%), coronal synostosis (18%), metopic (5%), lambdoidal (5%), and multiple suture synostosis (MSS) (13%). ISS and MSS populations demonstrated divergent outcomes. Eighty-nine percent of MSS patients moved to a higher HC percentile curve postoperatively, and all experienced absolute HC increases. Fifty percent of ISS patients moved to a lower HC percentile curve postoperatively, the only synostosis subset to do so. The remaining ISS patients were divided evenly among stable (27%) and increased (23%) HC percentile groups.

Conclusions: Serial HC measurement may meaningfully quantify the efficacy and degree of surgical correction for craniosynostosis. In MSS, multi-dimensional suture release may relieve restrictions on normal brain development and correspond with increased calvarial growth. The scaphocephalic deformity of ISS, by contrast, leads to a disproportionately increased HC relative to cranial vault volume preoperatively. Sagittal suture release restores a more anatomic, spherical cranial vault volume relationship and continued normal growth. Decreased percentile HC growth, as demonstrated by our study population, may therefore represent a successful surgical result in ISS patients.

Keywords:
craniosynostosis
calvarial growth
surgical treatment
pediatrics

CNS 2006

Revision And Explantation Strategies Involving The Charite Artificial Disc

Authors:
Scott P. Leary, MD; Todd Hopkins Lanman, MD; John J. Regan, MD

Introduction: The purpose of this study is to characterize the etiology and strategies utilized when a revision or explantation procedure is necessary following a failure of lumbar total disc replacement with the Charité intervertebral prosthesis.

Methods: A retrospective analysis of 17 consecutive cases over a four-year period was performed. Each case involved a primary revision or explantation procedure involving a Charité intervertebral prosthesis.

Results: We analyzed 17 consecutive cases referred to the senior author for revision surgery. 14 of 17 cases required removal of the implant and conversion to a fusion. In three cases, primary revision of the implant was performed. Early revision was performed in 7 cases (7-14 days) all as a result of implant displacement. 10 late revisions were performed from 6 weeks to 2 years. Technical errors during initial implant surgery were felt to be the cause of implant dislocation or failure in 8 cases. In 4 cases the artificial disc procedure was contraindicated due to end stage facet disease or spondylolisthesis. In 5 cases, implant dislocation occurred as a result of a fall or trauma.
Implant revision strategies were determined by the length of time from the original surgery and the location of the implant. All early revisions from 7 to 14 days were managed using the original retroperitioneal incision. Late revisions required a variety of approaches. Ureteral stenting was utilized for the L4-5 approaches. Preoperative vascular studies were performed in cases of late dislocation. There were no vascular, ureteral or neurologic injuries and no blood transfusions were required.

Conclusions: Factors that contribute to unsuccessful total disc replacement are primarily performing the procedure in contraindicated patients and technical errors of original implantation. The most common technical errors are use of an oversized implant or anterior positioning of the implant. In our series, revision surgery was successful in all cases.

Format:
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Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Anthony K. Kim; Michael Y. Wang; Carlos Ledezma; Alex Tagva; David Nicholas; Robert Wykoff

Introduction: We investigate the use of magnetic resonance myelogram (MrM) and SPECT in selecting inflamed facets and predicting a favorable response to lumbar facet injection.

Methods: Twenty-one consecutive patients (110 facets) with severe axial back pain underwent lumbar MRI prior to facet injection. Noninvasively, MrM was reconstructed from fine-cut coronal T2W images. Facets were segregated using a previously described grading system based on synovial architecture and content. Patient outcome was evaluated with standard pain scale questionnaire at 2 weeks.

Results: Of 110 facets, 29 facets demonstrated the following findings: (a) bright T2W synovial signal (b) cartilaginous abnormality forming a mottled synovial pattern (c) synovial fluid out of proportion to that normally seen in the synovial space. Sensitivity and specificity for MrM to independently identify these facets were 0.83 and 1.0 (P = 0.0001). 89% of patients with positive MrM reported significant relief of pain post injection. During a 4-month period, 8 of 10 patients with (+) MrM re-requested facet injections for pain relief.

Conclusions: MrM had a 92% positive predictive value and a 100% negative predictive value for detecting fluid surrounding a subset of facets. These facets have bright T2WI signal, cartilaginous mottled abnormalities and often have synovial fluid out of proportion to standard. Such facets were noted to be (+) SPECT in a previous study (0. 90 specificity, p = 0.0001). Fluid accumulation and increased blood flow were confirmed in a subset of facets via SPECT findings and MrM. MrM may be a valuable adjunct in the detection of inflamed facet joints.

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CNS 2006 Annual Meeting Chicago

Introduction: We performed a study to assess the safety and stability of deformity correction from a solely posterior approach with placement of anterior cages and posterior segmental fixation in one operation.

Methods: 23 patients who failed brace trial for at least 6 months were included in the series. All patients had progressive neurologic deficit or evidence of deformity progression at time of operation. All patients underwent a single operation in the prone position. Transpedicular segmental fixation was accompanied by anterior column reconstruction using either expandable or stackable cages without nerve root sacrifice. Stackable cages were used for high thoracic deformity. Deformity Cobb angle and plain radiograph evaluation of fusion ensued for mean follow-up 15 months.

Results: All patients achieved correction of deformity without undue complications. Improved or maintained ASIA scores were noted in all patients. Mean operation time was 316 min +/- 34.5 S.D, or, ~ 5 hours. Pre-op deformity mean Cobb angle was 26 deg +/- 9.2 S.D. Postop mean angle was 12.1 deg +/- 4.5 SD with resultant mean deformity correction of 14.2 deg +/- 6.8 SD. At mean 15 month follow-up, no patients demonstrated loss of deformity correction. Plain radiographic evidence suggestive of fusion was noted in all patients. Some degree of neurological dysfunction was present due to spinal cord compression in all but four patients. Of the 19 patients with deficits, three were unchanged after surgery. The remainder experienced improvements. Fifteen advanced one ASIA grade and one improved two grades. No patients experienced neurological deterioration.

Conclusions: Delayed kyphotic deformity correction of the thoracolumbar spine is achieved via a posterior-only approach. Posterior segmental fixation and anterior column reconstruction was performed in one surgical setting without the need for nerve root sacrifice when using stackable versus expandable cages. At 15 months, post-surgical Cobb angles remained stable. Improved fusion criteria and further follow-up will be required to determine fusion and loss of correction rates over time.

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CNS 2006 Annual Meeting Chicago

Authors:
Michael Y. Wang; Anthony K. Kim; Hassan A Serhan, PhD; H.B. Seim; Simon Turner

Introduction: Facet degeneration is commonly observed in the aging population. However, little is known about the natural history, etiological factors, and clinical significance of facet arthrosis. One barrier to investigation in this area has been the paucity of animal models. Moore, et al. demonstrated the induction of facet degeneration through annular rim lesioning in a sheep model, but produced only mild histopathological arthritic changes after greater than one year. The goal of this study was to develop and refine a large animal model of accelerated facet joint arthrosis through disruption of the anterior vertebral column.

Methods: Sixteen skeletally mature Rambouillet Columbian ewes were utilized in the experimental group. Sheep were maintained in strict accordance with animal care guidelines in open range. Surgical disruption of the anterior column was performed with a large annulotomy via a retroperitoneal approach, leaving the posterior spinal elements completely undisturbed. Three adjacent disc levels were lesioned. Animals were sacrificed at 3 (n=2), 6 (n=4), 9 (n=4), and 12 (n=6) months. Spiral CT and MRI analysis of the bony and soft tissue structures after animal sacrifice
Results: Radiographic findings of the posterior elements in the experimental group were compared with animals that had not undergone surgery. Those in the experimental group demonstrated progressive radiographic evidence of posterior element degeneration. This included enlargement of the bony articular process, osteophytic lipping, and loss of the synovial space and fluid signal. The posterior bony elements hypertrophied an average of 24% on axial CT images.

Conclusions: This study demonstrates that disruptions in anterior column integrity can lead to accelerated changes in the posterior joint structures. The changes occur within twelve months and radiographically resemble the changes seen in human degenerative disease. This model may prove useful for studying the pathological process of facet arthrosis and interventions to reduce these changes.

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Digital Poster
Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Bryan C. Oh, MD; Allan Christopher Heller, MD; James B. Elder, MD; Michael Y. Wang, MD; Charles Y. Liu; Steven L. Giannotta, MD

Introduction: The traditional Swan-Ganz catheter, a mainstay of management in patients with aneurysmal subarachnoid hemorrhage, uses a standard bolus thermodilution technique to measure cardiac output. Recently, a continuous cardiac output (CCO) Swan-Ganz catheter was developed to provide rapid and accurate assessment of the response of critically ill patients to various treatments. To our knowledge, nobody has assessed the use of the CCO Swan-Ganz catheter in management of patients with aneurysmal subarachnoid hemorrhage.

Methods: Between January 2004 and January 2006, 97 patients were admitted to USC University Hospital with the diagnosis of aneurysmal subarachnoid hemorrhage. We review our results of invasive CCO monitoring in this patient population.

Results: CCO Swan-Ganz catheters were inserted into 43 (10 male, 33 female; ages 28-81, mean 60.7) of the 97 (25 male, 72 female) patients studied. In 38 of these patients, catheter insertion was done for triple-H therapy guidance after transcranial doppler and CT angiography results confirmed clinically suggested vasospasm. In 2 cases, catheter placement was performed for guidance of fluid management in patients with documented congestive heart failure (CHF). In the remaining 3 cases, catheters were placed for: 1)cardiac function monitoring in a patient with critical aortic stenosis, 2)fluid management in a patient who suffered a massive stroke after intraoperative rupture, 3)treatment guidance in a patient who suffered a cardiac arrest prior to transfer. Of the 38 patients who received triple-H therapy, 30 demonstrated neurological improvement. Both of the CHF patients, the patient with aortic stenosis, and the patient who suffered a cardiac arrest all showed improvement in their cardiopulmonary status. The patient who suffered a stroke died. Line sepsis occurred in 3 of the 43 cases. There were no other complications of catheter placement.

Conclusions: Invasive CCO monitoring is a safe and effective tool that can be used in the management of patients with aneurysmal subarachnoid hemorrhage.

Format:
Digital Poster
Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Bryan C. Oh, MD; Allan Christopher Heller, MD; Daniel J. Hoh, MD; Michael Y. Wang, MD; Charles Y. Liu; Steven L. Giannotta, MD

Introduction: Triple-H therapy is an accepted treatment for cerebral vasospasm. Traditionally, the standard Swan-Ganz catheter that uses a bolus thermodilution technique using cold saline has been used to guide triple-H therapy. Recently, a Swan-Ganz catheter capable of measuring continuous cardiac output (CCO) has been developed. However, nobody has used invasive CCO monitoring to guide triple-H therapy.

Methods: We report our experience with the CCO Swan-Ganz catheter in treatment of patients who developed vasospasm after aneurysmal subarachnoid hemorrhage (SAH). We analyzed data from patients admitted to our facility with the diagnosis of aneurysmal SAH from January 2004 to January 2006. Triple-H therapy was instituted in patients who demonstrated clinical evidence of vasospasm that was confirmed by both transcranial doppler and CT angiogram studies. Therapy goals were to keep the pulmonary capillary wedge pressure (PCWP) between 12-16 mm Hg and the cardiac index (CI) between 4-5 L/min/sq m.

Results: During this period, 97 patients (25 male, 72 female) were admitted to USC University Hospital with aneurysmal SAH. Of this group, 38 patients (9 male, 29 female; ages 28-81, mean 59.8) developed vasospasm and were treated with triple-H therapy. On average, triple-H therapy commenced 5.3 days after the SAH occured and lasted for 7.7 days. Thirty of 38 patients demonstrated improvement in neurologic function after triple-H therapy. Of these 30 patients, 10 underwent cerebral angioplasty. Of the 8 patients who did not improve after triple-H therapy, 4 underwent cerebral angioplasty. Final disposition of these 38 patients was as follows: 9 home, 13 acute inpatient rehabilitation, 13 skilled nursing facility, 3 died. Regarding complications of triple-H therapy, there were 2 cases of myocardial infarction and 2 cases of line sepsis. Additionally, 1 patient required a durotomy for increased intracranial pressure.

Conclusions: Invasive CCO monitoring is an effective and safe guide of triple-H therapy for patients with cerebral vasospasm.

Format:
Digital Poster
Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Mark N. Jabbour, MD; Christian G. Samuelson, BS; James B. Elder, MD; Charles Y. Liu; Florence M. Hofman, PHD; Steven L. Giannotta, MD

Introduction: Brain arteriovenous malformations (BAVMs) have been reported to be highly angiogenic, proinflamatory lesions, often prone to hemorrhage and continuous expansion over time. In order to understand the mechanisms of this pathology, we have successfully characterized the angiogenic properties of AVM-BEC and identified significant differences between these cells and control brain endothelial cells (BEC).

Methods: Purified AVM-BEC were grown on cover glass slides for 2 days, and stained with the following angiogenic markers: endothelin-1(ET-1), VEGF-A, VEGF-R1, VEGF-R2, VE-Cadherin and integrin avb3. Immunostaining was evaluated using HSCORE, which quantifies intensity and percent distribution of staining (percent intensity unit= piu). Control BEC were isolated from epilepsy surgical specimens. Data were analyzed by paired Student’s t test and reported as means +/- standard deviation.

Results: Our results demonstrate that AVM-BEC in comparison to BEC expressed significantly higher levels of ET-1 (HSCORE= 422.9 +/- 29.6piu versus 285.7 +/- 35.5 piu; P = 0.02) and VEGF-A (HSCORE= 444.5 +/- 51.7 piu versus 301.8 +/- 30.6 piu; P = 0.02). There was no difference in VEGF-R1 (flt-1) expression between AVM-BEC and control BEC (HSCORE= 379.2 +/- 56.1piu versus 310.3 +/- 12.8 piu; P = 0.16), however VEGF-R2 (flk-1) was significantly decreased (HSCORE= 280.7 +/- 7.5 piu versus 373.3 +/- 15.6 piu; P < 0.01). The expression of the tight junction protein, VE-Cadherin was decreased (HSCORE= 244.7 +/- 31.0 piu versus 406.4 +/- 15.5 piu; P < 0.01), while integrin (avb3) was strongly expressed in AVM-BEC compared to control BEC (HSCORE= 391.3 +/- 38.4 piu versus 192.7 +/- 42.3 piu; P < 0.01).

Conclusions: AVM-BECs demonstrate upregulation of a variety of pro-angiogeneic growth factors and receptors, as well as different structural molecules compared to control BEC.

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CNS 2006 Annual Meeting Chicago

Authors
Mark N. Jabbour, MD; Christian G. Samuelson, BS; James B. Elder, MD; Charles Y. Liu; Steven L. Giannotta, MD; Florence M. Hofman, PHD

Introduction: Arteriovenous malformation in the brain exhibit significant vascular abnormalities. To understand the mechanisms involved in this aberrant vasculature, we investigated arteriovenous malformation brain-derived endothelial cells (AVM-BEC) and showed that these cells express different morphologic and phenotypic characteristics compared to normal brain-derived endothelial cells (BEC). Based on these studies, the functional potential of AVM-BEC in tubule formation and cell migration, was analyzed for specific angiogenic properties, and demonstrated to be significantly different from BEC.

Methods: Isolated, purified, and characterized AVM-BEC were used in the in vitro angiogenesis tubule formation, using the standard 3-dimensional matrix. Cells were labelled with a green fluorescent dye (CFDA-SE). The average cell length/tubule is reported. AVM-BEC were tested for migration, using the modified Boydon chamber technique. Control BEC were isolated from epilepsy surgical specimens. Data were analyzed using the paired student’s t test for tubule formation and one-way ANOVA test for migration assay.

Results: The results show that AVM-BEC migrate faster than BEC [F(3,36) = 64; P < 0.01]. Treatment with angiogenic factor IL-8 (1ng/ml) caused faster migration of BEC while AVM-BEC migrated less [F(3,36) = 64; P < 0.01]. In the tubule formation assay, AVM-BEC failed to form normal tubule-like structures (43.3 ± 9.4um versus 65.9 ± 10.6um; P < 0.01) as observed in BEC cultures. Treatment with VEGF (10ng/ml) or TGF-B (10ng/ml) enhanced tubule formation in BEC (97.1 ± 31.1um; P = 0.02, and 81.5 ± 22.0um; P = 0.02, respectively), however in AVM-BEC no tubules were observed.

Conclusions: These results demonstrate that AVM-BEC have aberrant angiogenic functions compared to BEC. AVM-BEC cannot form proper tubules; and these cells appear to migrate at a faster rate than BEC. AVM-BEC have distinct functional properties, that are different from BEC.

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CNS 2006 Annual Meeting Chicago

Authors:
Christian G. Samuelson, BS; Mark N. Jabbour, MD; James B. Elder, MD; Charles Y. Liu; Florence M. Hofman, PHD; Steven L. Giannotta, MD

Introduction: Brain Arteriovenous malformations (BAVMs) represent a unique cerebrovascular pathology whereby arteries are directly connected to veins without evidence of capillary plexus formation. The goal of this study is to identify differences between endothelial cells derived from BAVMs compared to normal brain endothelial cells (BEC).

Methods: BAVM endothelial cells, were obtained from surgical specimens of AVM lesions. BEC controls were obtained from epilepsy surgical specimens. This population was isolated and characterized using flow cytommetry (F.A.C.S), and immunohistochemical staining procedures. Stained slides were graded using the HSCORE method, which quantifies intensity and percent distribution of staining (percent intensity unit= piu). Cell proliferation was assessed using Ki-67 staining and calculating the percent of positive cells. Data were analyzed by paired Student’s t test and reported as means +/- standard deviation.

Results: We characterized both AVM-BEC and control BEC by staining for endothelial specific markers CD31 and FVIII, and sorting for acetylated LDL-receptor, resulting in greater than 95% purity. AVM-BEC expressed a higher Ki-67 proliferative index than BEC (62 +/- 13% versus 15 +/- 3%; P < 0.01), which represented a 4-fold increase in the number of dividing cells. AVM-BEC have an altered cell morphology in comparison to BEC, and express significantly decreased levels of CD105 (Endoglin) (HSCORE = 200 +/- 1piu versus 360 +/- 53piu; P < 0.01) and eNOS (endothelial nitric oxide synthase) (HSCORE = 109 +/- 3piu versus 461.7 +/- 15.3piu; P = 0.01).

Conclusions: We have successfully isolated and characterized a pure population of AVM-BEC. Furthermore, we showed that these AVM-BEC have different phenotypic characteristics compared to normal brain endothelial cells.

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Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
James B. Elder, MD; Michael Y. Wang

Introduction: Patients who undergo lumbar spine procedures frequently experience significant, debilitating pain related to their surgery. This pain may delay postoperative mobilization, increase length of hospitalization and require prolonged use of high doses of narcotics. Use of a local anesthetic continuous-infusion pump after surgery may lead to improvement in these outcome variables.

Methods: After posterior lumbar spine fusion procedures, 26 consecutive patients received continuous infusion of 0.5% marcaine into the sub-fascial aspects of the wound via an elastomeric pump. Data were collected prospectively by third party assessment using standard nursing protocols. This included pain scores and opiate use over the first 5 post-operative days, length of hospitalization, and complications. Retrospective analysis compared each study patient to a case-control patient. Variables such as age, gender, and surgical procedure were similar between matched cases.

Results: Patients receiving continuous local anesthetic infusion used 21.5% less narcotics on post-operative day 1, 37.4% less on day 2, and 26% less on day 3 compared to control patients. Differences in opiate usage were negligible on post-operative day 4 (0.04% greater) and 5 (0.07% greater). A lower average pain score was observed among the study patients on each post-operative day: 23.9% less pain on day 1, 19.0% on day 2, 17.8% on day 3, 16.8% on day 4, and 40.4% on day 5. No differences were observed in length of hospitalization or complications.

Conclusions: Patients with a local anesthetic continuous-infusion device used less narcotics than case-control patients over the first 3 postoperative days, and reported lower pain scores during the first 5 postoperative days. These results suggest that continuous infusion of local anesthetic into the paravertebral tissue during the immediate postoperative period is a safe and effective technique that achieves lower pain scores and narcotic use. Further data may reveal additional benefits such as decreased times to mobility and functional independence.

Format:
Open Paper
Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Gabriel Zada, MD; Eisha Christian, BS; Steven L. Giannotta, MD

Introduction: Since their conception in 1969, fenestrated aneurysm clips have become useful tools in the surgical clip ligation of a wide spectrum of aneurysms. The use of the fenestrated aneurysm clip for aneurysms of the Anterior Communicating Artery was reviewed in order to identify particular situations that surgeons may be more likely to utilize fenstrated clips for securing AComm aneurysms.

Methods: A retrospective patient record review was conducted to identify patients undergoing surgical clip ligation of an AComm Artery aneurysm with the use of a fenestrated aneurysm clip between 1990-2005. Data was reviewed and subsequenlty analyzed.

Results: Two hundred four patients that underwent surgical clipping of an AComm Artery aneurysm were identified. Of these patients, fenestrated aneurysm clips were used in 17 cases (8%). The majority of aneurysms pointed superiorly or posteriorly, and the mean aneurysm size was 9 mm. The following structures were included in the clip aperture: Ipsilateral A2 artery, 11 patients (66%); Ipsilateral A1 artery, 4 patients (23%); Recurrent artery of Heubner, 1 patient (6%), Frontopolar artery, 1 patient (6%). Aneurysms approached from the left side more frequently required fenestrated clips than did right-sided aneurysms (76 versus 24%, p=0.0053). All 17 patients demonstrated patency of the A2 vessels on postoperative angiography.

Conclusions: The fenestrated aneurysm clip has become an integral tool in the surgical clipping of complex AComm Artery aneurysms. As an ever growing number of these lesions are treated by coil embolization, more complex aneurysms cases are being referred for surgical clipping. For large or superiorly pointing aneurysms, the use of a fenestrated clip may allow the surgeon to limit tedious and potentially dangerous dissection of adherent branch vessels, while maintaining the integrity of structures placed in the fenestration.

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Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Gabriel Zada, MD; Julia Breault, BS; Steven L. Giannotta, MD
Introduction: Fetal variant posterior cerebral arteries (Fetal PCAs) have been reported to occur in approximately 21% of the population. Internal Carotid Artery (ICA) aneurysms arising from the origin of fetal variant posterior cerebral artery aneurysms (Fetal PCAs) require special attention as obliteration of a Fetal PCA is more likely to result in neurological deficits with a wider distribution of cerebral ischemia.

Methods: A retrospective chart review was conducted for all patients undergoing surgical clipping of a posterior communicating artery (PComm) aneurysm at LAC-USC Medical Center over a fifteen year period (1991-2005), in order to identify cases with aneurysms originating from fetal variant PCAs. Data was retrospectively reviewed and analyzed.

Results: Of the 189 patients that had PComm aneurysm treated surgically over a fifteen period, 24 patients (13%) were identified with aneurysms originating at the origin of fetal variant PCAs. Two of these patients had bilateral fetal PCA variants. Aneurysms were left sided in 12 cases and right sided in 12 cases. The mean aneurysm size was 6 mm. The mean ischemia time with temporary clipping (12 cases) was 4.5 minutes. Intraoperative rupture occurred in 6 cases (25%). Postoperative angiography demonstrated occlusion of the fetal PCA in 1 case (4%), with an ensuing occipital infarct yet no clinical sequelae.

Conclusions: It is important to identify the presence or absence of fetal PCA variants on preoperative imaging studies. Aneurysms occurring at the takeoff of fetal PCA vessels are frequently encountered in a distribution expected based on previous studies. Aneurysms originating from the ICA at the takeoff of a Fetal variant PCA may pose a more substantial risk for infarction and subsequent neurological deficit with surgical or endovascular obliteration. The presence of a fetal variant PCA aneurysm may lend support to opting for surgical clip ligation over endovascular occlusion of these aneurysms.

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Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Azadeh Farin

Introduction: Onyx, a radiopaque nonadhesive liquid embolizate, has had successful applications in peripheral, intracranial and spinal AVMs; one wide-necked renal aneurysm; and peripheral pseudoaneurysms. Onyx is composed of ethylene vinyl alcohol copolymer, and solidifies upon blood contact forming a compressible embolus. Here we demonstrate feasibility and efficacy of Onyx embolization of dural AVFs.

Methods: During 2006, Onyx was used in two procedures to treat two patients with dural AVFs. Case 1: A 53-year-old male presented with syncope, pulsatile tinnitus, and seizures. Imaging revealed a dural AVF at the right transverse-sigmoid sinus junction supplied by the right occipital artery and drained by the right superior petrosal sinus. Case 2: A 73-year-old male with headache had a dural AVF in the right interhemispheric fissure supplied by right middle meningeal and superficial temporal arteries with veins draining to the sagittal sinus.

Results: Onyx embolization was successful in both cases. In Case 1, the AVF was occluded entirely with preservation of transverse sinus patency. In Case 2, flow was reduced 95-99%; remaining feeders were too small to embolize. This patient experienced embolizate reflux, limiting migration of Onyx deeper into the lesion. Both patients remained at neurologic baseline and experienced symptom/sign improvement without adverse events including recurrent hemorrhage. Neither case exhibited angiographic evidence of distal nontargeted embolization.

Conclusions: Preliminary data suggests Onyx is safe and effective for embolization of dural AVFs. Onyx is advantageous over conventional agents because its nonadhesive, low viscosity nature facilitates deep, extensive penetration into the plethora of small feeding vessels before it coagulates proximally, making a one-injection cure possible. Other agents solidify prior to penetrating the entire target, providing only proximal embolization. While Onyx’ low viscosity may conversely potentiate disastrous nontarget embolization and its long-term efficacy requires further study, its unique properties make it a potentially promising agent for cure of cerebral vascular malformations.

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Meeting:
CNS 2006 Annual Meeting Chicago

Authors:
Laurence Davidson, MD; Mark D. Krieger, MD; J. Gordon McComb, MD; Ira Bowen, BA

Introduction: Langerhans cell histiocytosis (LCH) typically presents to the neurosurgeon with the identification of a lesion of the skull or vertebrae, or with diabetes insipidus. LCH is a rare disease of unknown etiology, affecting primarily infants and children. The disease course can be quite variable, affecting one or multiple organ systems and ranging from benign to fulminant. Eosinophilic granuloma, Hand-Schuller-Christian disease and Letterer-Siwe disease are all forms of LCH. Disease course following the identification of a lesion with neurosurgical consequences is poorly quantified.

Methods: To determine disease course after identification of a lesion of the neuroaxis we retrospectively reviewed 67 children with LCH treated by a pediatric neurosurgical department over a 25 year period.

Results: This series included 72% boys and 28% girls, ranging in age from 6 months to 13 years (average 5.6 years). Follow-up ranged from 4 months to 25 years, with an average of 3.5 years. 88% had skull lesions, 8% had spine lesions and 4% had lesions in the hypothalamic-pituitary axis. No patients died of their disease. 80% of the patients had unifocal disease at presentation of which 10% developed multifocal disease. 20% of the patients were found to have multifocal disease at presentation, 60% of which developed new lesions during the follow-up period. Time to disease progression ranged from 2 months to 3 years. Age less than 5 years at the time of initial presentation was a risk factor for both multifocality and progression. All patients with multifocality or progression had their disease controlled by chemotherapy.

Conclusions: This large and unique series of patients with LCH demonstrates the need for extent of disease evaluation both at presentation and at follow-up. Young patients who present with multifocal disease are much more likely to progress and will require systemic therapy to control their disease.

Format:
Digital Poster (View)
Meeting:
CNS 2006 Annual Meeting Chicago

Abstract: 2006 Nov 29
Cavarial Growth Following Surgical Treatment of Craniosynostosis
Author(s):
Alex Khalessi,MD, Los Angeles, CA
Mark D. Krieger,MD, Childrens Hospital Los Angeles, Los Angeles, CA
Ira Bowen,BA, Los Angeles, CA
J. Gordon McComb,MD, Los Angeles, CA

Introduction: Calvarial growth may represent a viable outcome measure for the surgical treatment of craniosynostosis.

Methods:117 children were surgically treated for craniosynostosis at a single institution from 2000 to 2005. Head circumference(HC) measurements were retrospectively reviewed pre-operatively, immediately post-operatively(1-2weeks), and at short-term follow-up (6months to 1year). Using population-based HC growth curves, data points were assigned a percentile score. Subjects were classified into three post-operative outcome states: (1)patient HC remained stable,(2)patient HC moved to a lower percentile growth curve, and (3)patient HC moved to a higher growth curve.

Results: Study population descriptive statistics were as follows: mean age 9months, gender breakdown: 26% female and 74% male,and follow-up from 3 to 56months (mean 18months). Subsets included: isolated sagittal synostosis(ISS)(59%),coronal synostosis(18%),metopic(5%),lambdoidal(5%),and multiple suture synostosis(MSS)(13%). ISS and MSS populations demonstrated divergent outcomes. Eighty-nine percent of MSS patients moved to higher HC percentile curves post-op,all experienced absolute HC increases. 50% of ISS patients moved to a lower HC percentile curve post-op,the only synostosis subset to do so. Remaining ISS patients divided evenly among stable(27%) and increased(23%) HC-percentile groups.

Conclusions: Serial HC measurement may meaningfully quantify the efficacy and degree of surgical correction for craniosynostosis. In MSS,multi-dimensional suture release may relieve restrictions on normal brain development and correspond with increased calvarial growth. The scaphocephalic deformity of ISS,by contrast,leads to a disproportionately increased HC relative to cranial vault volume preoperatively. Sagittal suture release restores a more anatomic,spherical cranial vault volume relationship and continued normal growth. Decreased percentile HC growth,as demonstrated by our study population, may therefore represent a successful surgical result in ISS patients.

Keywords:
craniosynostosis
calvarial growth
surgical treatment
Article ID: 40517

Introduction: Delayed hyponatremia is frequently encountered following transsphenoidal pituitary surgery. Asymptomatic hyponatremia may occur more frequently than has been previously suspected, yet may be amenable to outpatient intervention in order to prevent the onset of symptoms.

Methods: 241 patients undergoing transsphenoidal pituitary surgery at USC University Hospital had screening serum sodium levels drawn as outpatients on postoperative day 7. Patient records were reviewed to determine the incidence and risk factors for hyponatremia.

Results: 23% of patients were found to be hyponatremic on postoperative day 7. The majority (80%) were asymptomatic. The incidence of symptomatic hyponatremia for all outpatients was 5%. The mean sodium level of symptomatic patients was 120.5 mEq/L, compared with 128.4 mEq/L in asymptomatic, hyponatremic patients (p less than 0.0001). Females were more likely to develop hyponatremia than males (33% versus 22%, p less than 0.03). Patients with transient DI in the early postoperative course were at greater risk for developing delayed hyponatremia (52% versus 21%, p less than 0.001). Age, tumor type, and tumor size did not correlate with the incidence of hyponatremia. The majority of asymptomatic patients responded to outpatient dietary modifications. 11 symptomatic patients were readmitted- all responded to fluid restriction with or without intravenous hypertonic saline.

Conclusions: Delayed hyponatremia occurs more frequently than has been previously suspected following transsphenoidal surgery, yet the majority of patients remain asymptomatic. A serum sodium value obtained one week following surgery on an outpatient basis is beneficial in the diagnosis, risk-stratification, and implementation of preventative dietary correction of hyponatremia.

Keywords:
Pituitary
Hyponatremia
SIADH
Transsphenoidal
Article ID: 36009

Introduction: Langerhans cell histiocytosis (LCH) is a rare disease whose course and optimal treatment are not fully known. The goal of this study was to review a large series of LCH patients with cranio-spinal lesions in order to assess the long-term course, outcome and efficacy of treatment of the disease.

Methods: Forty-four patients with LCH who presented to a single pediatric neurosurgical department between 1976 and 2005 were retrospectively reviewed.

Results: This series included 29 boys and 15 girls, ranging in age from 2 months to 13 years (average 5 years). The mean follow-up was 4.5 years. Twenty-seven (61%) had unifocal bone lesions, 12 (27%) had multifocal bone disease, 2 (4.5%) had lesions in the hypothalamic-pituitary axis, and 3 (7%) had multiple organ involvement. Five of the patients (17%) with unifocal disease at presentation had subsequent development of new lesions. Four of the patients (33%) with multifocal bone disease at presentation had delayed development of new lesions during the follow-up period. Two of the 3 patients (66%) with multiple organ LCH died. Age less than 2 years at the time of initial presentation was a risk factor for both multifocality and dissemination.

Conclusions: This series of LCH patients demonstrates the need for extent of disease evaluation both at presentation and follow-up. Patients with unifocal LCH can be effectively treated with surgery alone; however, systemic therapy should be considered for dissemination. Very young patients are more likely to have multifocal disease and diseminations, and will usually require systemic therapy to control their disease.

Keywords:
Langerhans cell histiocytosis
Histiocytosis X
outcome analysis
pediatric neurosurgery
Article ID: 40440

Introduction: Papillary glioneuronal tumor (PGNT) was initial described in 1998. A total of 23 cases have been reported. All have had benign clinical courses. We are presenting two patients with aggressive clinical courses.

Methods: A retrospective review of the case histories of two patients with PGNT treated between 2000 and 2006 was undertaken. The clinical histories, imaging studies, and histology were reviewed. Previously published case reports/series were also reviewed.

Results: Patient 1 was 13 years-old and patient 2 was 7 years-old, both females. On MRI both lesions were large (5-9cm) cystic tumors, with rim/nodular enhancement, minimal edema, and extension to the ventricular system. The cyst fluid was hypointense on T1 and hyperintense on T2 with faint septations. Patient 1 had a gross total resection while patient 2 had a sub-total resection. The histology showed a bimodal population of cells. A pseudopapillary area with a central hylanized vessel surrounded by single layer of cells that stained for vimentin and GFAP (astrocytic). A second portion containing variable sized cells that stained for synaptophysin and PGP 9.5 (glial). Patient 1 had multifocal recurrence 4 years after surgery. All lesions resolved within 18 months with fractionated radiation and chemothrapy (temador). Patient 2 had progression of residual disease within 3 months of resection. The proliferative indices (Ki-67) were 5% and 4%, respectively. Previously cited proliferative indices for PGNT's were <.5% to 3%.

Conclusion: We are reporting an aggresive variant of PGNT's that is identical to previously described PGNT histologically but with a higher proliferative index than previously described.

Keywords:
papillary glioneuronal tumor
aggressive
radiation
chemotherapy
Article ID: 40451

Introduction: Outcomes after repeated transsphenoidal surgery for recurrent/residual endocrine-inactive pituitary adenomas (EIAs) are inadequately described.

Methods: We performed a retrospective review of all patients with recurrent/residual EIAs operated at UCSF from 1975 to 1995. Primary outcome measures were initial extent of resection and long-term tumor recurrence.

Results: Of 104 total patients, 85 were residual and 19 were recurrent EIAs. The median time from initial surgery was 3.9 yrs. Suprasellar extension was observed in 58% and cavernous sinus invasion in 23% of cases. Patients that underwent second surgery were selected for analysis (N=92): 60 (65%) received a subtotal resection (STR) and 32 (35%) had a gross total resection (GTR). Thirty-nine patients (40%) received post-operative radiotherapy. Multivariate predictors for STR were STR at initial surgery (OR=5.7, 95%CI=1.7-19, P=0.004) and cavernous sinus invasion (OR=2.7, 95%CI=1.5-8.0, P=0.02). Age, sex, prior radiation, time from initial surgery, prior radiotherapy, tumor size, and histopathological subtype were not associated with STR. During a median follow-up of 5.25 yrs, 16 patients in this cohort had a re-recurrence requiring a third transsphenoidal removal. The total 5-year progression-free probability was 0.81. Cox regression analysis demonstrated that STR and no post-operative radiation were independently associated with increased recurrence (HR= 12, 95%CI 2.6-58, P=0.001; HR=8.2, 95%CI=2.1=31, P=0.001; respectively).

Conclusions: Even though transsphenoidal surgery for residual/recurrent EIAs is associated with higher recurrence rates compared to surgery for primary EIAs, it still offers good long-term tumor control. Patients with STR of a recurrent EIA should be considered for radiotherapy/radiosurgery.

Keywords:
pituitary adenoma
long-term outcome
endocrine-inactive
nonfunctioning
Article ID: 36283

Introduction: Surgery for clip ligation of anterior circulation aneurysms incurs a significant risk for new motor deficit caused by ischemia to motor cortex or pathways during temporary occlusion, permanent clipping or retraction. The standard techniques for monitoring such ischemic changes is somatosensory evoked potential (SSEP) monitoring. Transcranial motor evoked potential (TcMEP) monitoring may improve detection of impending ischemic changes intraoperatively.

Methods: Use of transcranial motor evoked potential (TcMEP) monitoring was evaluated via retrospective chart review of all cases of anterior circulation aneurysms clipped at this institution since the consistent additional use of intraoperative TcMEP monitoring. Initially 86 patients were considered; after exclusion criteria were applied, 76 patients remained in the analysis.

Results: Intraoperative electrophysiologic changes associated with temporary clipping occurred in 18% (14/76) of patients. Isolated TcMEP changes were seen in only one patient (1%) and in association with SSEP changes in 6 patients (8%). SSEP changes alone were seen in 7 patients. Signal changes returned to baseline with removal of temporary clips in all patients with TcMEP changes and all but one patient with SSEP changes. Post-operative neurologic deficits were noted in 83% of patients with changes in both modalities, 71% with TcMEP changes and 62% with SSEP changes.

Conclusions: The results suggest that TcMEP changes are more likely to be associated with post-operative neurologic deficit, especially if associated with SSEP changes. Therefore, intraoperative transcranial motor evoked potential monitoring during aneurysm surgery may offer improved prediction of ischemic changes in cortical and subcortical areas responsible for motor function.

Keywords:
Aneurysm
Motor Evoked Potential
Article ID: 36008

Introduction: While it is increasingly clear that facet arthropathy is a significant contributor to axial back pain, a major barrier to understanding this disease has been the lack of studies elucidating the relationship between structural degenerative facet changes and evidence of active joint inflammation. This study investigates structural (MRI) characteristics that predict pathology on functional (SPECT) imaging.

Methods: 431 patients without spondylolisthesis underwent SPECT imaging for chronic back pain. 31 patients had at least one “hot lesion." Exclusion of areas affected by surgery yielded 32 positive joints out of a total of 230 facets. Qualitative features were evaluated, including synovial and cartilaginous discontinuities, heterogeneous bone patterns, synovial hooking, and cupping osteophyte formation in the lateral joint. Quantitative features were evaluated, including asymmetry in size, joint space narrowing, lateral & medial synovial content, and variations in synovial signal intensity.

Results: The MRI characteristic with the greatest sensitivity was synovial space obliteration or narrowing (0.93 sensitivity and 0.35 specificity). Several facet morphologies were highly specific but not sensitive: lateral cupping from osteophytic overgrowth (0.90), and synovial mottling (0.90). Facet asymmetry and enlargement correlated poorly (sensitivity & specificity = 0.50), suggesting that joint hypertrophy may be protective and represent a more advanced stage in natural history of joint degeneration.

Conclusions: Abnormal synovial patterns were the best predictors of “hot” facets. This study suggests that specific abnormalities in the bony, cartilaginous, and synovial architecture may give future insight into the pathophysiology of facetogenic pain syndromes and the natural history of facet degeneration from synovial degeneration to facet enlargement.

Keywords:
degenerative
facet
SPECT
pain
Article ID: 34644

Introduction: The risk of focal infarction and postoperative neurologic deficit secondary to induced temporary occlusion of local arterial flow during microsurgical dissection of anterior circulation aneurysms was analyzed. The correlation between temporary clip time and electrophysiologic data, as well as with postoperative infarct, was studied.

Methods: Anterior circulation aneurysms clipped at this institution since using motor evoked potentials (MEPs) were retrospectively reviewed. Of 86 cases performed 2003-5, 55 included temporary clips. Patients with and without changes in electrophysiologic monitoring and postoperative infarctions were compared based on temporary clip time.

Results: Intraoperatively, five patients had MEP changes and ten patients had SSEP (somatosensory evoked potential) changes. Sixteen percent suffered infarction, and 25% demonstrated a focal neurologic deficit within 24 hours postoperatively. The mean temporary occlusion time was 10 minutes for patients without infarction versus 13 minutes for patients with infarction. 80% of MEP changes and 70% of SSEP changes occurred at 11 minutes or greater of temporary clip time. Of those without MEP changes, 57% had less than 11 minutes clip time. Of those without SSEP changes, 61% had less than 11 minutes clip time. Only 21% with less than 11 minutes occlusion exhibited postoperative infarcts, compared with 35% of patients with 11 minutes or greater occlusion. Conclusions: Surgery for clip ligation of anterior circulation aneurysms is associated with an increased risk for postoperative infarct and change in electrophysiologic data due to ischemia secondary to temporary clip time of 11 minutes or greater. Reliable electrophysiologic monitoring may limit deficits associated with prolonged temporary clip time.

Keywords:
intracranial aneurysm
temporary clip time
electrophysiologic monitoring
postoperative neurologic deficit
Article ID: 33881

Introduction: Head injury is a common presentation in children suffering from non-accidental trauma (NAT). Radiographic imaging, if demonstrating intracranial injury, may increase suspicion for NAT. The objectives of our study were to assess: 1) the frequency of imaging in children with head trauma 2) the incidence of positive radiographic findings of intracranial injury, 3) the occurrence of NAT evaluation in patients with or without evidence of intracranial injury.

Methods: We reviewed 475 consecutive records of patients presenting to a children’s emergency room in a 5 month period with the diagnosis of “head injury,” “head trauma,” “fall,” or “suspected child abuse.” Head CT and skull x-ray findings were recorded. NAT evaluation (skeletal survey, ophthalmologic exam) and notification of the Suspected Child Abuse and Neglect (SCAN) team were reported.

Results: Head CT or skull x-rays were performed in 176 of 475 patients (36%). 32 of 176 (18%) had evidence of skull fracture; 26 of 176 (15%) demonstrated intracranial injury. 41 (9%) underwent evaluation for NAT (25 skeletal surveys, 4 ophthalmologic exams, 29 SCAN investigations). 2 of 25 skeletal surveys showed other injuries. 1 of 4 ophthalmologic exams found retinal hemorrhages. 34 of 41 patients (83%) investigated for NAT had a negative head CT or no brain imaging. Only 3 of 29 (10%) patients referred for SCAN team investigation had a positive head CT.

Conclusions: Radiographic evidence of intracranial injury in pediatric head trauma is uncommon. The absence of radiographic findings, however, does not preclude the need for NAT evaluation if clinical suspicion warrants further investigation.

Keywords:
pediatric
head injury
non-accidental trauma
radiographic imaging
Article ID: 36208

Introduction: Advanced biomaterials offer the promise of specific signaling interactions with living tissue. We have developed an artificial extracellular matrix (AECM) protein designed to engineer the environment of the cell and influence its fate. This study examines the in vivo immunological response to this protein.

Methods: Thirty-six Sprague-Dawley rats were divided into three cohorts. The “AECM” and “Silastic” cohorts underwent subcutaneous implantation of an AECM protein and silicone elastic, respectively. The “sham” cohort underwent skin incision without implantation. Animals were sacrificed at 1, 4, or 12 weeks. Tissue from each lesion was fixed in 10% formalin and stained with hematoxylin and eosin.

Results: At 1 week, the AECM cohort showed both lymphocytic and foreign body giant cell infiltrates compared to fibrosis and chronic inflammation in the Silastic cohort. The sham cohort showed acute and chronic inflammation with early fibrosis. Inflammatory response in the AECM cohort increased at 1 month before finally diminishing to resemble that of the Silastic cohort, which, along with the sham group, had not changed significantly since the original samples. The amount of AECM protein remaining after 1 month was 30% and after 3 months 0%. The amount of Silastic did not diminish over time.

Conclusions: The subcutaneous inflammatory response to our AECM protein is, initially, more pronounced than with Silastic and leads to early degradation of the material. Loss of the implant over time may or may not be a detrimental quality. Whether a similar response would be seen in neural tissue has not been determined.

Keywords:
Artificial Protein
Biomaterials
Extracellular Matrix
In Vivo Response
Article ID: 36036