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Maxwell Boakye, Sean C. Huckins, Nikolaus M. Szeverenyi, Bobby I. Taskey and Charles J. Hodge Jr.

Object. Functional magnetic resonance (fMR) imaging was used to determine patterns of cerebral blood flow changes in the somatosensory cortex that result from median nerve stimulation (MNS).

Methods. Ten healthy volunteers underwent stimulation of the right median nerve at frequencies of 5.1 Hz (five volunteers) and 50 Hz (five volunteers). The left median nerve was stimulated at frequencies of 5.1 Hz (two volunteers) and 50 Hz (five volunteers). Tactile stimulation (with a soft brush) of the right index finger was also applied (three volunteers). Functional MR imaging data were transformed into Talairach space coordinates and averaged by group. Results showed significant activation (p < 0.001) in the following regions: primary sensorimotor cortex (SMI), secondary somatosensory cortex (SII), parietal operculum, insula, frontal cortex, supplementary motor area, and posterior parietal cortices (Brodmann's Areas 7 and 40). Further analysis revealed no statistically significant difference (p > 0.05) between volumes of cortical activation in the SMI or SII resulting from electrical stimuli at 5.1 Hz and 50 Hz. There existed no significant differences (p > 0.05) in cortical activity in either the SMI or SII resulting from either left- or right-sided MNS. With the exception of the frontal cortex, areas of cortical activity in response to tactile stimulation were anatomically identical to those regions activated by electrical stimulation. In the SMI and SII, activation resulting from tactile stimulation was not significantly different (p > 0.05) from that resulting from electrical stimulation.

Conclusions. Electrical stimulation of the median nerve is a reproducible and effective means of activating multiple somatosensory cortical areas, and fMR imaging can be used to investigate the complex network that exists between these areas.

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Mark H. Bilsky, Maxwell Boakye, Frederic Collignon, Dennis Kraus and Patrick Boland

Object. The authors describe the preoperative assessment, intraoperative strategies, and long-term outcomes in 41 consecutive patients who underwent spinal reconstruction after resection of subaxial cervical neoplasms.

Methods. Thirty-three tumors were metastatic and eight were primary. Preoperative studies included direct laryngoscopy and vertebral artery (VA) balloon occlusion tests in selected patients. Based on the tumor location, approaches included 12 anterior, 13 posterior, and 16 combined. All patients underwent aggressive intralesional resection and spinal reconstruction. In 12 patients, the VA was dissected from the periphery of the tumor, two cases of which required ligation. Fibula allograft and an anterior rigid plate fixation were most commonly used for anterior reconstruction. Posterior reconstruction was initially performed using lateral mass plates (LMPs) in 13 patients and screw/rod systems in the remaining patients.

At follow up, pain level improved to mild or was absent in 39 patients (95%) who had presented with moderate or severe pain. The American Spinal Injury Association (ASIA) Scale scores were stable in 25 patients who presented with ASIA Score E and improved in 14 patients (88%) who presented with ASIA Score B, C, or D. Functional radiculopathy significantly improved in 16 (94%) of 17 patients.

Complications occurred in 10 patients (24%) and included three fixation failures requiring revision. Two fixation failures involved cervical LMP screw pullout. The overall mean survival duration was 8.6 months for patients with metastatic tumors and 33.4 months for primary tumors.

Conclusions. Surgery for the treatment of subaxial spine neoplasms is effective for relieving pain, encouraging functional nerve root recovery, and preserving spinal cord function with acceptable complication rates.

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Maxwell Boakye, Praveen V. Mummaneni, Mark Garrett, Gerald Rodts and Regis Haid

Object. The authors reviewed clinical and radiographic outcomes in patients who had undergone anterior cervical discectomy and fusion (ACDF) involving the placement of polyetheretherketone (PEEK) spacers filled with recombinant human bone morphogenetic protein (rhBMP)—2.

Methods. Data obtained in 24 cases were retrospectively evaluated. The follow-up period ranged from 12 to 16 months (mean 13 months). Fifteen patients presented with radiculopathy, eight with myeloradiculopathy, and one with quadriparesis. Single-level ACDF was performed in 12 patients, two-level ACDF in nine, and three-level ACDF in three. Clinical outcomes were assessed using Odom criteria, and fusion was assessed by examining flexion—extension radiographs and computerized tomography scans in cases in which arthrodesis was questionable. Follow-up data were available for 23 patients. One patient died of medical complications unrelated to surgery 4 weeks after ACDF. Clinical outcomes were rated as good/excellent in 22 patients (95%) and fair in one (5%). Solid radiographically documented fusion, with evidence of solid bridging bone and no instability on flexion—extension x-ray films, was present in all cases. Complications included transient recurrent laryngeal nerve injury in one case, transient C-5 paresis in one, cerebrospinal fluid leakage in one, and transient dysphagia in two.

Conclusions. Analysis of the results indicated that ACDF involving an rhBMP-2—filled PEEK spacer leads to good clinical outcomes (by Odum criteria) and solid fusion (even in multilevel cases) while avoiding the complications associated with harvesting iliac crest bone grafts.

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Shivanand P. Lad, Chirag G. Patil, Christopher Ho, Michael S. B. Edwards and Maxwell Boakye

Object

Previous investigations of health outcome after spinal surgery for tethered cord syndrome (TCS) have been single-institution studies. The aim of this study was to report inpatient complications and outcomes on a nationwide level.

Methods

The Nationwide Inpatient Sample (NIS) was used to identify patients who underwent spinal surgery for TCS in the US between 1993 and 2002. Patients who had a primary diagnosis of TCS (ICD-9 742.59) and also underwent spinal laminectomies were included in this study. Multivariate analysis was performed to analyze the effects of patient and hospital characteristics on variables such as mortality rate, nonfatal complications, LOS, and adverse outcomes in general (defined as death or discharge to an institution rather than home).

Results

The NIS sample included data on 9733 patients with TCS who underwent surgery. The means for mortality rate, complication rate, and LOS, respectively, were 0.0005%, 9.48%, and 5.6 days. Postoperative hemorrhages or hematomas (mean rate 2.3%) were the most common complications reported. Age and complications were the only significant predictors of adverse outcome on multivariate analysis. Patients older than 65 years had a threefold increase in risk of adverse outcome compared with patients 18 to 44 years of age. On average, one postoperative complication led to a 3-day increase in mean LOS and added more than $9000 to hospital charges.

Conclusions

This study provides a national perspective on inpatient complications and outcomes after spinal surgery for TCS in the United States. The authors have demonstrated the impact of age, complications, and medical comorbidities on the outcome of surgery for patients with this common disorder.

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Chirag G. Patil, Shivanand P. Lad, Griffith R. Harsh, Edward R. Laws Jr. and Maxwell Boakye

Object

Information about complications, patient outcomes, and mortality rate after transsphenoidal surgery (TSS) for Cushing's disease has been derived largely from single-institution series. In this study the authors report on inpatient death, morbidity, and outcomes following TSS for Cushing's disease on a national level.

Methods

All patients in the Nationwide Inpatient Sample (NIS) database who had undergone transsphenoidal resection of a pituitary tumor for Cushing's disease between 1993 and 2002 were included in the study. The number of cases per year, length of stay (LOS), and rates of inpatient complications, death, and adverse outcomes (death or discharge to institution other than home) were abstracted. Univariate and multivariate analyses were performed to determine the effects of patient and hospital characteristics on outcome measures.

Results

According to the NIS, there were an estimated 3525 cases of TSS for Cushing's disease in the US between 1993 and 2002. During this period, there was a trend toward a small increase in the number of TSSs for Cushing's disease. The in-hospital mortality rate was 0.7%, and the complication rate was 42.1%. Diabetes insipidus (15%), fluid and electrolyte abnormalities (12.5%), and neurological deficits (5.6%) were the most common complications reported. Multivariate analysis showed that complications were more likely in patients with pre-operative comorbidities. Patients older than 64 years were much more likely to have an adverse outcome (odds ratio [OR] 20.8) and a prolonged hospital stay (OR 2.2). Women were less likely than men to have an adverse outcome (OR 0.3). A single postoperative complication increased the mean LOS by 3 days, more than tripled the odds of an adverse outcome, and increased the hospital charges by more than US $7000.

Conclusions

The authors provided a national perspective on trends, inpatient complications, and outcomes after TSS for Cushing's disease in the US. Postoperative complications had a significantly negative effect on LOS, adverse outcome, and resource utilization. Advanced age and multiple preoperative comorbidities were identified as important risk factors, and their effects on patient outcomes were quantified.

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Shivanand P. Lad, Chirag G. Patil, Eleonora Maries Lad and Maxwell Boakye

Object

Pathological vertebral fractures (PVFs) are an increasingly important cause of disability and have many clinical and economic implications. The authors examined trends in epidemiology and surgical management of pathological vertebral fractures in the US between 1993 and 2004.

Methods

The Nationwide Inpatient Sample database was used to analyze data collected from 1993 through 2004 to determine general trends in PVFs. Patients with PVFs were identified using the appropriate International Classification of Diseases, 9th Revision (ICD-9) diagnostic code (ICD-9 733.13). Trends in vertebral augmentation procedures and spinal fusions as well as comparison with incidences of other major pathological fractures, such as hip and upper limb, were also examined.

Results

In 2004, there were more than 55,000 inpatient admissions for PVFs. The majority of patients admitted were women (78%) in the 65 to 84 year–age group (60%). Medicare accounted for greater than 80% of insurance, and nearly 50% of all patients were admitted from the emergency department. The mean duration of hospitalization has continued to decrease, from 8.1 days in 1993 to 5.4 days in 2004. The mortality rate has remained relatively constant at approximately 1.5%. The discharge disposition has continued to change with an increasing number of patients being discharged to other institutions such as nursing homes and rehabilitation facilities. There was a staggering increase in the number of vertebral augmentation procedures performed between 1993 and 2004. The “national bill” for inpatient hospitalizations for PVFs totaled $1.3 billion in 2004.

Conclusions

With the continued aging of the population, PVFs represent an important cause of disability and a significant source of healthcare resource utilization.

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Gordon Li, Chirag Patil, John R. Adler, Shivanand P. Lad, Scott G. Soltys, Iris C. Gibbs, Laurie Tupper and Maxwell Boakye

Object

By targeting the medial branches of the dorsal rami, radiofrequency ablation and facet joint injections can provide temporary amelioration of facet joint–producing (or facetogenic) back pain. The authors used CyberKnife radiosurgery to denervate affected facet joints with the goal of obtaining a less invasive yet more thorough and durable antinociceptive rhizotomy.

Methods

Patients with refractory low-back pain, in whom symptoms are temporarily resolved by facet joint injections, were eligible. The patients were required to exhibit positron emission tomography–positive findings at the affected levels. Radiosurgical rhizotomy, targeting the facet joint, was performed in a single session with a marginal prescription dose of 40 Gy and a maximal dose of 60 Gy.

Results

Seven facet joints in 5 patients with presumptive facetogenic back pain underwent CyberKnife lesioning. The median follow-up was 9.8 months (range 3–16 months). The mean planning target volume was 1.7 cm3 (range 0.9–2.7 cm3). A dose of 40 Gy was prescribed to a mean isodose line of 79% (range 75–80%). Within 1 month of radiosurgery, improvement in pain was observed in 3 of the 5 patients with durable responses at 16, 12, and 6 months, respectively, of follow-up. Two patients, after 12 and 3 months of follow-up, have neither improved nor worsened. No patient has experienced acute or late-onset toxicity.

Conclusions

These preliminary results suggest that CyberKnife radiosurgery could be a safe, effective, and non-invasive alternative to radiofrequency ablation for managing facetogenic back pain. No patient suffered recurrent symptoms after radiosurgery. It is not yet known whether pain relief due to such lesions will be more durable than that produced by alternative procedures. A larger series of patients with long-term follow-up is ongoing.

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James Xie and Maxwell Boakye

Electrophysiological measures can provide information that complements clinical assessments such as the American Spinal Injury Association sensory and motor scores in the evaluation of outcomes after spinal cord injury (SCI). The authors review and summarize the literature regarding tests that are most relevant to the study of SCI recovery—in particular, motor evoked potentials and somatosensory evoked potentials (SSEPs). In addition, they discuss the role of other tests, including F-wave nerve conductance tests and electromyography, sympathetic skin response, and the Hoffman reflex (H-reflex) test as well as the promise of dermatomal SSEPs and the electrical perceptual threshold test, newer quantitative tests of sensory function.

It has been shown that motor evoked potential amplitudes improve with SCI recovery but latencies do not. Somatosensory evoked potentials are predictive of ambulatory capacity and hand function. Hoffman reflexes are present during spinal shock despite the loss of tendon reflexes, but their amplitudes increase with time after injury. Further, H-reflex modulation is reflective of changes in spinal excitability. While these tests have produced data that is congruent with clinical evaluations, they have yet to surpass clinical evaluations in predicting outcomes. Continuing research using these methodologies should yield a better understanding of the mechanisms behind SCI recovery and thus provide potentially greater predictive and evaluative power.

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Shivanand P. Lad, Justin G. Santarelli, Chirag G. Patil, Gary K. Steinberg and Maxwell Boakye

Object

Spinal arteriovenous malformations (AVMs) are rare and understudied vascular lesions that cause neurological insult by mass effect, venous obstruction, and vascular steal. These lesions are challenging entities to treat because of their complicated anatomy and physiology. Current management options include open microsurgery, endovascular embolization, and stereotactic radiosurgery.

Methods

Our study used the National Inpatient Sample database to analyze outcome data for spinal AVMs treated nationwide over an 11-year period from 1995 through 2006. Trends in procedural management, hospital course, and epidemiology of spinal AVMs are investigated.

Results

Annually, an average of 300 patients presented with spinal AVMs requiring hospital treatment. The average length of hospital stay for this treatment has declined from more than 9 days in 1995 to 6 days in 2006. However, the average cost of a hospital stay has increased from < $30,000 to nearly $70,000. Whereas one-half of spinal AVMs were treated operatively in 1995, one-third were managed operatively in 2006.

Conclusions

Spinal AVMs are being increasingly treated by endovascular, radiosurgical, or combined means. A discussion of modern strategies to treat these disorders is presented.

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Paul Kalanithi, Ryan D. Schubert, Shivanand P. Lad, Odette A. Harris and Maxwell Boakye

Object

This study provides the first US national data regarding frequency, cost, and mortality rate of traumatic subdural hematoma (SDH), and identifies demographic factors affecting morbidity and death in patients with traumatic SDH undergoing surgical drainage.

Methods

A retrospective analysis was conducted by querying the Nationwide Inpatient Sample, the largest all-payer database of nonfederal community hospitals. All cases of traumatic SDH were identified using ICD-9 codes. The study consisted of 2 parts: 1) trends data, which were abstracted from the years 1993–2006, and 2) univariate analysis and multivariate logistic regression of demographic variables on inhospital complications and deaths for the years 1993–2002.

Results

Admissions for traumatic SDH increased 154% from 17,328 in 1993 to 43,996 in 2006. Inhospital deaths decreased from 16.4% to 11.6% for traumatic SDH. Average costs increased 67% to $47,315 per admission. For the multivariate regression analysis, between 1993 and 2002, 67,864 patients with traumatic SDH underwent operative treatment. The inhospital mortality rate was 14.9% for traumatic SDH drainage, with an 18% inhospital complication rate. Factors affecting inhospital deaths included presence of coma (OR = 2.45) and more than 2 comorbidities (OR = 1.60). Increased age did not worsen the inhospital mortality rate.

Conclusions

Nationally, frequency and cost of traumatic SDH cases are increasing rapidly.