Alan T. Villavicencio

Cerebrospinal Fluid Shunt Survival and Etiology of Failures: A Seven-Year Institutional Experience

Background: Innovations in shunt technology and neuroendoscopy have been increasingly applied to shunt management. However, the relative life span of shunts and the etiology of shunt failure have not been characterized recently. Methods: We reviewed the records of all shunting procedures at our institution between January 1992 and December 1998. Independent predictors of shunt failure were analyzed via multivariate Cox regression analysis in 836 shunting procedures. Independent predictors of the etiology of failure (infection, proximal obstruction, distal malfunction) were analyzed via multivariate logistic regression analysis in the 383 shunts which failed. Results: A total of 353 pediatric patients underwent 308 shunt placements and 528 revisions. The risk (hazard ratio; HR) of shunt failure decreased as a function of time in both primary placements and revised shunts. In failed shunts, the odds of infection decreased 4-fold per year of shunt function, while the odds of distal malfunction increased 1.45-fold per year. Increasing number of shunt revisions (HR 1.31, p < 0.05), decreasing patient age in years (HR 1.04, p < 0.001), gestational age <40 weeks (HR 2.15, p < 0.001) but not the etiology of hydrocephalus were associated with an increased risk of shunt failure. Revisions versus primary placements, Dandy-Walker cysts and gestational age <40 weeks were independently associated with proximal, distal and infectious causes of failure, respectively. Conclusions: The long-term shunt revision rates observed here are similar to those reported over the past 2 decades. Shunt life span remains poorer in shunt revisions and in younger patients. Patient characteristics may suggest a specific risk and mechanism of failure, aiding in the long-term management of shunted hydrocephalus.

Endoscopic lateral transpsoas approach to the lumbar spine

Study Design. A description of a novel surgical approach to the lumbar spine and a prospective evaluation of the early surgical outcomes. Objectives. Describe the early postoperative results and the operative technique of a new, minimally invasive transpsoas approach for anterior fusion of the lumbar spine that minimizes the risk to large vessels and other critical structures. Summary of Background Data. Standard anterior endoscopic approaches to the lumbar spine require mobilization of the great vessels and sympathetic plexus. Vascular injury and retrograde ejaculation are complications clearly associated with this approach. A retroperitoneal, transpsoas approach to the lumbar spine may reduce these risks. Methods. From 1996 to 2002, 21 patients (13 females, 8 males; mean age 50.0 years) underwent an endoscopic, retroperitoneal transpsoas approach for exposure of the lumbar spine. Surgical indications included discogenic pain in 14 patients, spinal instability at a level adjacent to a previous fusion in 3 patients, and progressive degenerative scoliosis in 4 patients. Data were reviewed to document the early postoperative results for this procedure. Illustrations were created to clearly describe this approach. Results. Average operative time for the single level cases was 149 minutes (range 120–170 minutes); blood loss was 150 cc (range 50–650); postoperative hospital stay was 4.1 days. At long-term follow-up, visual analogue scale scores had decreased an average of 5.9. Mean follow-up was 3.1 years (range 2 months–6.0 years). Six patients (30%) experienced paresthesias in the groin/thigh region. Five of these same patients also complained of groin/thigh pain (27%). Two patients had symptoms that lasted longer than 1 month. One patient was converted to a mini-open lateral approach. There were no vascular injuries. Conclusions. Early results show the endoscopic lateral transpsoas approach to the lumbar spine to be a safe, minimally invasive method for anterior fusion of the first through the fourth lumbar vertebrae. Although there is a risk of groin/thigh numbness or pain, and these symptoms are mostly transient. This approach allows for exposure of the lumbar spine without mobilization of the great vessels or sympathetic plexus.

Perioperative complications in transforaminal lumbar interbody fusion versus anterior-posterior reconstruction for lumbar disc degeneration and instability.

Objectives Multiple different approaches are used to treat lumbar degenerative disc disease and spinal instability. Both anterior–posterior (AP) reconstructive surgery and transforaminal lumbar interbody fusion (TLIF) provide a circumferential fusion and are considered reasonable surgical options. The purpose of this study was to quantitatively assess clinical parameters such as surgical blood loss, duration of the procedure, length of hospitalization, and complications for TLIF and AP reconstructive surgery for lumbar fusion. Methods A retrospective analysis was completed on 167 consecutive cases performed between January 2002 and March 2004. TLIF surgical procedure was performed on 124 patients, including 73 minimally invasive and 51 open cases. AP surgery was performed on 43 patients. Patients were treated for painful degenerative disc disease, facet arthropathy, degenerative instability, and spinal stenosis. Results The mean operative time for AP reconstruction was 455 minutes, for minimally invasive TLIF 255 minutes, and open TLIF 222 minutes. The mean blood loss for AP fusion surgery was 550 mL, for minimally invasive TLIF 231 mL, and open TLIF 424 mL. The mean hospitalization time for AP reconstruction was 7.2 days, for minimally invasive TLIF 3.1 days, and open TLIF 4.1 days. The total rate of complications was 76.7% for AP reconstruction, including 62.8% major and 13.9% minor complications. The minimally invasive TLIF patients group had the total 30.1% rate of complications, 21.9% of which were minor and 8.2% major complications. There were no major complications in the open TLIF patients group, with 35.3% minor complications. Conclusions AP lumbar interbody fusion surgery is associated with a more than two times higher complication rate, significantly increased blood loss, and longer operative and hospitalization times than both percutaneous and open TLIF for lumbar disc degeneration and instability.

Laminectomy versus Percutaneous Electrode Placement for Spinal Cord Stimulation

OBJECTIVE The purpose of this study was to compare the long-term effectiveness of spinal cord stimulation using laminectomy-style electrodes versus that using percutaneously implanted electrodes. METHODS Forty-one patients underwent an initial trial period of spinal cord stimulation with temporary electrodes at Duke Medical Center between December 1992 and January 1998. A permanent system was implanted if trial stimulation reduced the patients pain by more than 50%. Median long-term follow-up after permanent electrode placement was 34 months (range, 6-66 mo). Severity of pain was determined postoperatively by a disinterested third party using a visual analog scale and a modified outcome scale. RESULTS Twenty-seven (66%) of the 41 patients participating in the trial had permanent electrodes placed. Visual analog scores decreased an average of 4.6 among patients in whom electrodes were placed via laminectomy in the thoracic region (two-tailed t test, P < 0.0001). Patients who underwent percutaneous placement of thoracic electrodes had an average decrease of 3.1 in their visual analog scores (two-tailed t test, P < 0.001). Electrodes placed through laminectomy furnished significantly greater long-term pain relief than did those placed percutaneously, as measured by a four-tier outcome grading scale (P = 0.02). CONCLUSION Spinal cord stimulation is an effective treatment for chronic pain in the lower back and lower extremities that is refractory to conservative therapy. Electrodes placed via laminectomy in the thoracic region appear to be associated with significantly better long-term effectiveness than are electrodes placed percutaneously.

Minimally invasive versus open transforaminal lumbar interbody fusion

Background Available clinical data are insufficient for comparing minimally invasive (MI) and open approaches for transforaminal lumbar interbody fusion (TLIF). To date, a paucity of literature exists directly comparing minimally invasive (MI) and open approaches for transforaminal lumbar interbody fusion (TLIF). The purpose of this study was to directly compare safety and effectiveness for these two surgical approaches. Materials and Methods Open or minimally invasive TLIF was performed in 63 and 76 patients, respectively. All consecutive minimally invasive TLIF cases were matched with a comparable cohort of open TLIF cases using three variables: diagnosis, number of spinal levels, and history of previous lumbar surgery. Patients were treated for painful degenerative disc disease with or without disc herniation, spondylolisthesis, and/or stenosis at one or two spinal levels. Clinical outcome (self-report measures, e.g., visual analog scale (VAS), patient satisfaction, and MacNabs criteria), operative data (operative time, estimated blood loss), length of hospitalization, and complications were assessed. Average follow-up for patients was 37.5 months. Results: The mean change in VAS scores postoperatively was greater (5.2 vs. 4.1) in theopen TLIF patient group (P = 0.3). MacNabs criteria score was excellent/good in 67% and 70% (P = 0.8) of patients in open and minimally invasive TLIF groups, respectively. The overall patient satisfaction was 72.1% and 64.5% (P = 0.4) in open and minimally invasive TLIF groups, respectively. The total mean operative time was 214.9 min for open and 222.5 min for minimally invasive TLIF procedures (P = 0.5). The mean estimated blood loss for minimally invasive TLIF (163.0 ml) was significantly lower (P < 0.0001) than the open approach (366.8 ml). The mean duration of hospitalization in the minimally invasive TLIF (3 days) was significantly shorter (P = 0.02) than the open group (4.2 days). The total rate of neurological deficit was 10.5% in the minimally invasive TLIF group compared to 1.6% in the open group (P = 0.02). Conclusions: Minimally invasive TLIF technique may provide equivalent long-term clinical outcomes compared to open TLIF approach in select population of patients. The potential benefit of minimized tissue disruption, reduced blood loss, and length of hospitalization must be weighted against the increased rate of neural injury-related complications associated with a learning curve.

The accuracy of pedicle screw placement using intraoperative image guidance systems

OBJECT Several retrospective studies have demonstrated higher accuracy rates and increased safety for navigated pedicle screw placement than for free-hand techniques; however, the accuracy differences between navigation systems has not been extensively studied. In some instances, 3D fluoroscopic navigation methods have been reported to not be more accurate than 2D navigation methods for pedicle screw placement. The authors of this study endeavored to identify if 3D fluoroscopic navigation methods resulted in a higher placement accuracy of pedicle screws. METHODS A systematic analysis was conducted to examine pedicle screw insertion accuracy based on the use of 2D, 3D, and conventional fluoroscopic image guidance systems. A PubMed and MEDLINE database search was conducted to review the published literature that focused on the accuracy of pedicle screw placement using intraoperative, real-time fluoroscopic image guidance in spine fusion surgeries. The pedicle screw accuracy rates were segregated according to spinal level because each spinal region has individual anatomical and morphological variations. Descriptive statistics were used to compare the pedicle screw insertion accuracy rate differences among the navigation methods. RESULTS A total of 30 studies were included in the analysis. The data were abstracted and analyzed for the following groups: 12 data sets that used conventional fluoroscopy, 8 data sets that used 2D fluoroscopic navigation, and 20 data sets that used 3D fluoroscopic navigation. These studies included 1973 patients in whom 9310 pedicle screws were inserted. With conventional fluoroscopy, 2532 of 3719 screws were inserted accurately (68.1% accuracy); with 2D fluoroscopic navigation, 1031 of 1223 screws were inserted accurately (84.3% accuracy); and with 3D fluoroscopic navigation, 4170 of 4368 screws were inserted accurately (95.5% accuracy). The accuracy rates when 3D was compared with 2D fluoroscopic navigation were also consistently higher throughout all individual spinal levels. CONCLUSIONS Three-dimensional fluoroscopic image guidance systems demonstrated a significantly higher pedicle screw placement accuracy than conventional fluoroscopy or 2D fluoroscopic image guidance methods.

Prospective, Randomized, Double-Blind Clinical Study Evaluating the Correlation of Clinical Outcomes and Cervical Sagittal Alignment

BACKGROUND:Sagittal alignment of the cervical spine has received increased attention in the literature as an important determinant of clinical outcomes after anterior cervical diskectomy and fusion. Surgeons use parallel or lordotically fashioned grafts depending on preference or simple availability. OBJECTIVE:To quantitatively assess and compare cervical sagittal alignment and clinical outcome when lordotic or parallel allografts were used for fusion. METHODS:A prospective, randomized, double-blind clinical study that enrolled 122 patients was performed. The mean follow-up was 37.5 months (range, 12-54 months). RESULTS:The mean postoperative cervical sagittal alignment was 19° (range, −7°-36°) and 18° (range, −7°-37°) in the lordotic and parallel graft patient groups, respectively. The mean segmental sagittal alignment was 6° (range, −4°-19°) and 7° (range, −3°-19°) in the lordotic and parallel graft patient groups, respectively. There were no statistically significant differences in clinical outcome scores between the lordotic and parallel graft patient groups. However, patients who had maintained or improved segmental sagittal alignment, regardless of graft type, achieved a higher degree of improvement in Short Form-36 Physical Component Summary and Neck Disability Index scores. This was statistically significant (P < .038). CONCLUSION:The use of lordotically shaped allografts does not increase cervical/segmental sagittal alignment or improve clinical outcomes. Maintaining a consistent segmental sagittal alignment or increasing segmental lordosis was related to a higher degree of improvement in clinical outcomes.

Utility of computerized isocentric fluoroscopy for minimally invasive spinal surgical techniques.

Objective: The purpose of this study was to prospectively evaluate the clinical utility and accuracy of intraoperative three-dimensional fluoroscopy as an adjunct for the placement of a complex spinal instrumentation. Methods: The Siemens Iso-C three-dimensional fluoroscopy unit in the combination with the Stealth Treon computer volumetric navigational system was used. A total of 279 spinal instrumentation screws or transpedicular cannulations were performed in 69 patients. Accuracy, operative time, and amount of fluoroscopy utilization time were assessed for transforaminal lumbar interbody fusion (TLIF) and kyphoplasty cases. Results: Only 4 percutaneous transpedicular lumbar screws out of 265 total (1.5%) were malpositioned. Average operative time for TLIF cases was 185 minutes (range 114-311 minutes) for one-level and 292.6 minutes (range 173-390 minutes) for two-level procedures. Biplanar fluoroscopy utilization time was 93 seconds (range 27-280 seconds) for one-level procedures and 216 seconds (range 80-388 seconds) for two-level procedures. Average surgery duration for kyphoplasty was 60 minutes (range 36-79 minutes) for one-level procedures and 68.5 minutes (range 65-75 minutes) for two-level cases. Biplanar fluoroscopy utilization time was 41.3 seconds per case (range 25-62 seconds). Conclusions: Use of intraoperative three-dimensional fluoroscopy for image guidance in minimally invasive complex spinal instrumentation procedures is feasible and safe. This technique provides excellent visualization of three-dimensional relationships. This potentially results in improved accuracy of screw positioning and the ability to detect misplaced screws prior to wound closure. This technique also potentially results in a significant reduction in radiation exposure for both the patient and the staff.

CyberKnife radiosurgery for trigeminal neuralgia treatment: A preliminary multicenter experience

OBJECTIVERadiosurgery has gained acceptance as a treatment option for trigeminal neuralgia. We report our preliminary multicenter experience treating trigeminal neuralgia with the CyberKnife (Accuray, Inc., Sunnyvale, CA). METHODSA total of 95 patients were treated for idiopathic trigeminal neuralgia between May 2002 and October 2005. Radiosurgical dose and volume parameters were retrospectively analyzed in relation to pain response, complications, and recurrence of symptoms. Optimal treatment parameters were identified for patients who had excellent and sustained pain relief with no complications, including severe or moderate hypesthesia. RESULTSExcellent pain relief was initially experienced by 64 out of 95 patients (67%). The median time to pain relief was 14 days (range, 0.3–180 d). Posttreatment numbness occurred in 45 (47%) of the patients treated. Using higher radiation doses and treating longer segments of the nerve led to both better pain relief and a higher incidence of hypesthesia. The presence of posttreatment numbness was predictive of better pain relief. The overall rate of complications was 18%. At the mean follow-up time of 2 years, 47 of the 95 patients (50%) had sustained pain relief, all of whom were completely off pain medications. CONCLUSIONThe results of this study suggest the following optimal radiosurgical treatment parameters for treatment of idiopathic trigeminal neuralgia: a median maximal dose of 78 Gy (range, 70–85.4 Gy) and a median length of the nerve treated of 6 mm (range, 5–12 mm).

De Novo Cerebral Arteriovenous Malformation: Case Report

OBJECTIVE AND IMPORTANCE Arteriovenous malformations (AVMs) are generally thought to have a congenital cause. This is the first report of an angiographically proven de novo cerebral AVM in an adult patient without previous vascular abnormality. CLINICAL PRESENTATION A 26-year-old African-American woman developed multiple cranial nerve deficits and ataxia over the course of a few days after a streptococcal throat infection. T2-weighted magnetic resonance imaging scans revealed a hyperintense signal in the midbrain with extension into the diencephalon. A cerebral angiogram performed at that time to exclude vasculitis revealed normal cerebral vasculature. The patient was treated with corticosteroids, and symptoms resolved. Subsequently, at the age of 32, this patient presented with a severe headache and emesis, but with no focal neurological deficit. INTERVENTION The patient’s cranial computed tomographic and magnetic resonance imaging scans revealed a right posterior temporal intraparenchymal hemorrhage, and cerebral angiography revealed a new 3- by 2-cm AVM. The patient underwent microsurgical resection of the AVM and associated hematoma. Postoperative angiography revealed no evidence of residual AVM. CONCLUSION This study details the case of a woman who developed a de novo cerebral AVM during a 6-year period. This report challenges the conventional belief that all AVMs have a congenital cause.