Positron emission tomography with [18F]flutemetamol and [11C]PiB for in vivo detection of cerebral cortical amyloid in normal pressure hydrocephalus patients.

BACKGROUND AND PURPOSE: This study determined the correlation between uptake of the amyloid positron emission tomography (PET) imaging agent [(18) F]flutemetamol and amyloid-ß measured by immunohistochemical and histochemical staining in a frontal cortical biopsy. METHODS: Fifteen patients with possible normal pressure hydrocephalus (NPH) and previous brain biopsy obtained during intracranial pressure monitoring underwent [18F]flutemetamol PET. Seven of these patients also underwent [11C] Pittsburgh compound B (PiB) PET. [18F]Flutemetamol and [11C]PiB uptake was quantified using standardized uptake value ratio (SUVR) with the cerebellar cortex as a reference region. Tissue amyloid-ß was evaluated using the monoclonal antibody 4G8, Thioflavin-S and Bielschowsky silver stain. RESULTS: [18F]Flutemetamol and [11C]PiB SUVRs correlated with biopsy specimen amyloid-ß levels contralateral (r = 0.86, P < 0.0001; r = 0.96, P = 0.0008) and ipsilateral (r = 0.82, P = 0.0002; r = 0.87, P = 0.01) to the biopsy site. Association between cortical composite [(18) F]flutemetamol SUVRs and [11C]PiB SUVRs was highly significant (r = 0.97, P = 0.0003). CONCLUSIONS: [18F]Flutemetamol detects brain amyloid-ß in vivo with moderate to high sensitivity and high specificity. This agent, therefore, represents a valuable new tool to study and verify the presence of amyloid-ß pathology, both in patients with possible NPH and among the wider population.

Treating patients with documented atherosclerosis to National Cholesterol Education Program-recommended low-density-lipoprotein cholesterol goals with atorvastatin, fluvastatin, lovastatin and simvastatin.

OBJECTIVES: This study compared the efficacy and safety of atorvastatin, fluvastatin, lovastatin, and simvastatin in patients with documented atherosclerosis treated to U.S. National Cholesterol Education Program (NCEP) recommended low-density-lipoprotein (LDL) cholesterol concentration (< or = 100 mg/dl [2.59 mmol/liter]). BACKGROUND: For patients with advanced atherosclerosis, NCEP recommends lipid-lowering drug therapy if LDL cholesterol remains > or = 130 mg/dl (3.36 mmol/liter). METHODS: A total of 318 men or women with documented atherosclerosis and LDL cholesterol > or = 130 mg/dl (3.36 mmol/liter) and < or = 250 mg/dl (6.5 mmol/liter), and triglycerides < or = 400 mg/dl (4.5 mmol/liter) participated in this 54-week, multicenter, open-label, randomized, parallel-group, active-controlled, treat-to-target study. Patients were titrated at 12-week intervals until the LDL cholesterol goal was reached. Number of patients reaching target LDL cholesterol levels and dose to reach target were evaluated. RESULTS: At the starting doses, atorvastatin 10 mg produced significantly greater decreases (p < 0.05) in plasma LDL cholesterol than the other treatments. Subsequently, the percentage of patients reaching goal at the starting dose was 32% for atorvastatin, 1% for fluvastatin, 10% for lovastatin and 22% for simvastatin. Atorvastatin-treated patients required a lower median dose than other treatments. Median doses at week 54 with the last available visit carried forward were atorvastatin 20 mg/day, fluvastatin 40 mg/day + colestipol 20 g/day, lovastatin 80 mg/day, simvastatin 40 mg/day. CONCLUSIONS: A significantly greater number (p < 0.05) of patients with confirmed atherosclerosis treated with atorvastatin reached the target LDL cholesterol concentration at the starting dose than patients treated with fluvastatin or lovastatin, and significantly fewer (p < 0.05) patients treated with atorvastatin required combination therapy with colestipol to achieve target LDL cholesterol concentrations than all other statins tested.

Impaired glucose tolerance is normalized by treatment with the thiazolidinedione troglitazone.

OBJECTIVE: The primary purpose of this study was to assess the effects of 12 weeks of treatment with either troglitazone, an investigational thiazolidinedione that acts as an insulin-action enhancer, or placebo in patients with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: A total of 51 subjects with IGT between 24 and 77 years of age were enrolled in this multicenter, double-blind, placebo-controlled, parallel group study (troglitazone, 25 patients; placebo, 26 patients). Patients were randomly assigned to receive either 400 mg troglitazone (every morning [QAM]) or placebo (QAM). The main outcome measure was the oral glucose tolerance test (OGTT) assessing glucose, insulin, and C-peptide levels in the fasting state and every 30 min up to 2 h after ingesting the glucose load. Fasting serum levels of HbA1c, fructosamine, lipids, and blood pressure were also measured. RESULTS: A total of 46 patients completed the study. The glucose, insulin, and C-peptide responses after a glucose load were significantly reduced at 6 and 12 weeks in the troglitazone treatment group. After 6 weeks of treatment, 75% (n = 18) of those taking troglitazone had improved to normal glucose tolerance, whereas only 38% (n = 9) of those of placebo showed improvement (P = 0.008). After 12 weeks of treatment, 80% (n = 16) of the troglitazone treatment group had normalized their glucose tolerance, while only 48% (n = 10) of those on placebo had converted to normal (P = 0.016). Fasting triglyceride levels in the troglitazone treatment group had decreased by 40 mg/dl (0.45 mmol/l) (P = 0.0016). Other lipid measurements, blood pressure, glycosylated hemoglobin, and fructosamine were normal at baseline for both treatment groups and remained normal throughout the study. CONCLUSIONS: The glycemic response after a glucose load is statistically and clinically significantly improved for patients with IGT treated with troglitazone.

Nuclear clefting in dorsal root ganglion neurons: a response to whole body vibration.

Normal adult rabbits were studied in a whole body vibration model which simulates the type of environmental exposure associated with vibration-induced low back pain. This model has previously been shown to induce changes in pain-related neuropeptides in the dorsal root ganglion. Following two weeks of daily exposure to whole body vibration, dorsal root ganglia were excised from control and vibrated rabbits and prepared for ultrastructural evaluation. Of over 1,200 cells sampled, 190 appropriately sectioned cells were analyzed: 32 from immobilized controls, 44 from normal controls, and 114 from vibrated animals. Analysis of nuclear contours revealed more prevalent and more extensive clefting of the nuclear membrane in vibrated cells. The membrane lining these clefts was traversed by numerous pores; density of these pores was 46% greater than in adjacent nonclefted segments (p less than .001). Number of clefts per nucleus was increased by 39% in vibrated animals. Cleft area represented 1.19% of nuclear area in vibrated cells compared to 0.74% in controls (p less than .001). Numerous mitochondria and free ribosomes and abundant rough endoplasmic reticulum were located within the cleft spaces of vibrated cells. Pores in the cleft membrane appeared normal, supporting the conclusion that the clefts are structural alterations rather than fixation or sectioning artifacts. Changes in dorsal root ganglion neuropeptides seen in previous studies of vibrated animals may result from increased or redirected cellular synthesis. Ultrastructural changes seen in these vibrated dorsal root ganglion neurons are consistent with such an alteration in metabolism and could reflect increased synthesis of pain-related neuropeptides.

Efficacy and short-term safety of a new ACAT inhibitor, avasimibe, on lipids, lipoproteins, and apolipoproteins, in patients with combined hyperlipidemia.

Although acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors have been shown to reduce lipid levels in several animal models, the safety and lipid modifying activity of any single agent in this class has not been demonstrated in humans. The safety and efficacy of avasimibe (CI-1011), a new, unique, wholly synthetic ACAT inhibitor, was evaluated in the treatment of 130 men and women with combined hyperlipidemia and hypoalphalipoproteinemia (low levels of high-density lipoprotein cholesterol [HDL-C]). Following an 8-week placebo and dietary-controlled baseline period, patients were randomly assigned to double-blind treatment with placebo, 50, 125, 250, or 500 mg avasimibe administered as capsules once daily for 8 weeks. At all evaluated doses, avasimibe treatment resulted in prompt and significant reductions (P<0.05) in plasma levels of total triglycerides (TG) and very low-density lipoprotein cholesterol (VLDL-C) with mean reductions of up to 23% and 30% respectively, apparently independent of dose. No statistically significant changes in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), HDL-C or apolipoprotein (apo) B were detected. ApoAI levels were also unchanged on all doses of avasimibe apart from the 500 mg dosage, which was associated with a significant decrease in plasma apoAI. The relevance of this latter finding in only one dosage group is not known. All doses of avasimibe were well tolerated with no resulting significant abnormalities of biochemical, hematological, or clinical parameters.

Poisson regression analysis of the mortality among a cohort of World War II nuclear industry workers.

A historical cohort mortality study was conducted among 28,008 white male employees who had worked for at least 1 month in Oak Ridge, Tennessee, during World War II. The workers were employed at two plants that were producing enriched uranium and a research and development laboratory. Vital status was ascertained through 1980 for 98.1% of the cohort members and death certificates were obtained for 96.8% of the 11,671 decedents. A modified version of the traditional standardized mortality ratio (SMR) analysis was used to compare the cause-specific mortality experience of the World War II workers with the U.S. white male population. An SMR and a trend statistic were computed for each cause-of-death category for the 30-year interval from 1950 to 1980. The SMR for all causes was 1.11, and there was a significant upward trend of 0.74% per year. The excess mortality was primarily due to lung cancer and diseases of the respiratory system. Poisson regression methods were used to evaluate the influence of duration of employment, facility of employment, socioeconomic status, birth year, period of follow-up, and radiation exposure on cause-specific mortality. Maximum likelihood estimates of the parameters in a main-effects model were obtained to describe the joint effects of these six factors on cause-specific mortality of the World War II workers. We show that these multivariate regression techniques provide a useful extension of conventional SMR analysis and illustrate their effective use in a large occupational cohort study.

Conservative treatment of the scoliotic and kyphotic patient. Brace treatment and other modalities.

Although various forms of nonoperative treatment have been applied to spinal deformities over the centuries, it was the development of the original Milwaukee brace, a cervicothoracic-lumbosacral orthosis (CTLSO), by Blount and Schmidt in the middle 1940s that heralded a new era of nonoperative treatment and that has led to much of the success we enjoy with nonoperative treatment today. Furthermore, as our understanding of the natural history of scoliosis has grown and our recognition of the specific genetic, curvature-related, or neurophysiological factors that predispose patients to curvature progression has improved, so has our ability to successfully treat patients by nonoperative means.

Cost effectiveness of treatment to National Cholesterol Education Panel (NCEP) targets with HMG-CoA reductase inhibitors. Trial design.

HMG-CoA reductase inhibitors effectively reduce cholesterol levels, and this is associated with a lower rate of cardiovascular events. Some HMG-CoA reductase inhibitors are more effective than others in reducing low density lipoprotein (LDL) cholesterol, and such drugs should help patients achieve LDL cholesterol targets prescribed by the National Cholesterol Education Panel (NCEP). This paper describes the design of a trial comparing the clinical efficacy and cost effectiveness of four HMG-CoA reductase inhibitors in reducing LDL cholesterol to specified targets. This trial is being conducted in 30 physicians' practices in the USA. Its primary aim is to assess the resource use required to achieve and maintain NCEP targets by all patients randomised and followed up for one year.

The cost of reaching National Cholesterol Education Program (NCEP) goals in hypercholesterolaemic patients. A comparison of atorvastatin, simvastatin, lovastatin and fluvastatin.

OBJECTIVE: Recognising the importance of treating hyperlipidaemia, the National Cholesterol Education Program (NCEP) has established widely accepted treatment goals for low density lipoprotein cholesterol (LDL-C). Medications used most commonly to achieve these LDL-C goals are HMG-CoA reductase inhibitors. The relative resource utilisation and cost associated with the use of reductase inhibitors of different LDL-C lowering efficacy are unknown, but are major health and economic concerns. The objective of this study was to determine the mean total cost of care to reach NCEP goals with various reductase inhibitors. DESIGN: In a randomised, 54-week, 30-centre controlled trial we compared resources used and costs associated with treating patients to achieve NCEP goals using 4 reductase inhibitors: atorvastatin, simvastatin, lovastatin and fluvastatin. PATIENTS AND PARTICIPANTS: The trial studied 662 patients; 318 had known atherosclerotic disease. INTERVENTIONS: Reductase inhibitor therapy was initiated at recommended starting doses and increased according to NCEP guidelines and package insert information. For patients who did not reach the goal at the highest recommended dose of each reductase inhibitor, the resin colestipol was added. MAIN OUTCOME MEASURES AND RESULTS: Patients treated with atorvastatin, compared-with other reductase inhibitors, were more likely to reach NCEP goals during treatment (p < 0.05), required fewer office visits (p < 0.001) and less adjuvant colestipol therapy (p = 0.001). Consequently, the mean total cost of care (1996 values) to reach NCEP goals was lower with atorvastatin [$US1064; 95% confidence interval (CI): $US953 to $US1176] compared with simvastatin ($US1471, 95% CI: $US1304 to $US1648), lovastatin ($US1972; 95% CI: $US1758 to $US2186) and fluvastatin ($US1542; 95% CI: $US1384 to $US1710). Results were similar for patients with or without known atherosclerotic disease. CONCLUSIONS: In patients requiring drug therapy for hypercholesterolaemia, NCEP LDL-C goals are achieved significantly more often using fewer resources with atorvastatin compared with simvastatin, lovastatin or fluvastatin.

Early failure of short-segment pedicle instrumentation for thoracolumbar fractures. A preliminary report.

The results after treatment of fifty-two lumbar and thoracolumbar fractures with Cotrel-Dubousset instrumentation were reviewed as part of an ongoing study. Nineteen patients (average duration of follow-up, fifteen months) had been managed with short-segment pedicle-screw instrumentation. This preliminary report outlines the complications and pitfalls identified during the initial healing phase in this subgroup of patients. There were no neurological or vascular injuries due to placement of the pedicle screws, but ten patients had some form of failure of the fixation during the early period of healing. Failure of the fixation was manifested in three ways: progressive kyphosis secondary to the bending of screws (six patients), kyphosis secondary to osseous collapse or vertebral translation without bending of the hardware (three patients), and segmental kyphosis after a caudad screw in the lumbar construct broke (one patient, who had had a combined instrumentation for multiple fractures). Untreated anterior instability, and pre-stressing of the screws when the rods were contoured in situ, resulted in a high rate of failure. The high rate of failure of the hardware associated with this fixation construct suggests that posterior screw fixation alone may not be adequate when Cotrel-Dubousset instrumentation is used for short-segment lumbar arthrodeses. Bent screws or measurable kyphosis did not always herald a clinical failure, but patients who had progressive kyphosis of more than 10 degrees had substantially more pain than did those who had little or no progression. The results reported here are preliminary, and speculation as to the importance of these findings and as to the long-term outcome in these patients would be premature.(ABSTRACT TRUNCATED AT 250 WORDS)

Loading of pedicle screws within the vertebra.

We studied cadaveric motion segments instrumented with unique pedicle screw transducers and loaded in a corpectomy model. We hypothesized that the pedicle screw bending moments could be characterized using a mathematical model. Previous studies have estimated the loading characteristics of pedicle screws either by finite element analysis or by experimentally measuring the screw bending strains external to the lamina and pedicle. In our study, the L4 vertebra was instrumented with modified pedicle screws and fixation rods, and loaded axially. The screws were instrumented to measure bending moments at three locations along the threaded shaft of the screw. The recorded bending moments were maximum near the screw hub and decreased in a non-linear manner toward the screw tip. A mathematical model was fit to the bending moment data and accurately described the loading response of a pedicle screw within a vertebra. This model validates previously unsubstantiated analytical models and provides a tool for predicting which construct design variables contribute to pedicle screw failure. In addition, this experimental model should prove useful in validating finite element models designed to investigate vertebral loading of pedicle screws.

The effect of boundary conditions on experimentally measured trabecular strain in the thoracic spine.

Vertebral bodies are the primary structural entities of the spine, and trabecular bone is the dominant material from which vertebral bodies are composed. Understanding the mechanical characteristics of vertebral trabecular bone, therefore, is of critical importance in the many clinical conditions that affect the spine. Numerous studies have loaded vertebral bodies to investigate the influence of trabecular bone characteristics on deformation and failure patterns, but the methods of load application have been inconsistent. These differences in the method of load application are a potential confounding factor in the interpretation of the experimental results. We investigated this problem by measuring the distribution of minimum principal strain and maximum shear strain magnitude within 6.35 mm thick samples cut from thoracic spine segments (T8-T10) and loaded to simulate three common experimental configurations. Measurements were made using the texture correlation technique, which extracts deformation patterns from digitized contact radiographs of samples under load. The three loading configurations examined were a three-body construct, a single vertebral body loaded through sectioned intervertebral discs, and polymethylmethacrylate molded directly to the endplates. Results indicate that from both probability and spatial distribution standpoints the best simulation of in vivo loading generates the least uniform strains. Loading through disc remnants or through plastic molded to the endplates causes increasing degrees of strain homogenization. This result has implications not only for the design of experiments involving spinal loading, but also for theories concerning the adaptation of trabecular bone to functional loads.

Mechanoreceptor endings in human cervical facet joints.

Twenty-one cervical facet capsules, taken from three normal human subjects, were examined to determine the type, density, and distribution of mechanoreceptive nerve endings in these tissues. Clearly identifiable mechanoreceptors were found in 17 of 21 specimens and were classified according to the scheme for encapsulated nerve endings established by Freeman and Wyke. Eleven Type I, 20 Type II, and 5 Type III receptors were identified, as well as a number of small, unencapsulated nerve endings. Type I receptors were small globular structures measuring 25-50 microns in diameter. Type II receptors varied in size and contour, but were characterized by their oblong shape and broad, lamellated capsule. Type III receptors were relatively large oblong structures with an amorphous capsule, within which a reticular meshwork of fine neurites was embedded. Free (nociceptive) nerve endings were found in subsynovial loose areolar and dense capsular tissues. The presence of mechanoreceptive and nociceptive nerve endings in cervical facet capsules proves that these tissues are monitored by the central nervous system and implies that neural input from the facets is important to proprioception and pain sensation in the cervical spine. Previous studies have suggested that protection muscular reflexes modulated by these types of mechanoreceptors are important in preventing joint instability and degeneration. It is suggested that the surgeon take steps to avoid inadvertently damaging these tissues when exposing the cervical spine.

Endoscopically assisted decompression for metastatic thoracic neoplasms.

STUDY DESIGN: The author describes a technique for complete vertebrectomy and anterior decompression followed by a formal anterior column reconstruction, using readily available endoscopic instruments. This procedure is indicated in patients with radioresistant metastasis of the thoracic spine, particularly those involving the upper thoracic segments where a thoracotomy is difficult and causes a high rate of morbidity. This is also a suitable technique for patients with pulmonary disease who cannot tolerate a standard thoracotomy. OBJECTIVES: To demonstrate the feasibility and potential benefits of endoscopically controlled decompression through an extrapleural, posterolateral approach. SUMMARY OF BACKGROUND DATA: Posterolateral decompression of the thoracic spine offers potential advantages in comparison with traditional anterior-posterior procedures combining thoracotomy and posterior instrumentation, including decreased operative time, decreased morbidity, and reduced hospital stay. Results of previous studies have not demonstrated the same benefit for posterolateral decompression as for anterior vertebrectomy and decompression. Drawbacks to the traditional posterolateral decompressions have included poor visualization of the spinal cord and anterior tumor, poor access to tumor on the side contralateral to the approach, and the need to manipulate the spinal cord to completely remove adjacent tumor and tumor adherent to the dura. METHODS: Surgical indications, rationale, and technique are provided, and initial clinical results are described. RESULTS: Transpedicular decompression using endoscopy is described in five patients. The mean operative time for the combined procedure was 7.25 hours, with a mean blood loss of 1800 mL. Neurologic recovery and maintenance were excellent. Inpatient days averaged 7.5, and intensive care days averaged 2. One patient died of disease 8 months after surgery, and four were living, with disease, 3-24 months after surgery. CONCLUSIONS: Endoscopically assisted decompression can reduce morbidity, hospital stay, and treatment costs while matching the efficacy of traditional combined procedures. Endoscopy provides a readily available and easily applied tool that dramatically improves the surgeon's vision, providing light, magnification, and a direct view of remote structures.

Salvage of a malpositioned anterior odontoid screw.

STUDY DESIGN: Description of surgical technique with case correlation. OBJECTIVE: This article presents an alternative approach to anterior odontoid screw salvage in a patient with established nonunion. SUMMARY OF BACKGROUND DATA: Type II odontoid fractures are often treated surgically because of their risk of nonunion. Anterior odontoid screw fixation offers stable fixation without loss of atlantoaxial motion. Treatment failure may occur despite adequate screw placement but is more likely when fixation is inadequate. The traditional solution is a posterior fusion. In selected cases the surgeon may want to revise the anterior instrumentation with the hope of retaining as much C1-C2 motion as possible. METHODS: A 43-year-old man presented 16 months after Type II odontoid fracture treated by anterior odontoid screw fixation. He had neck pain, instability, and a pseudarthrosis confirmed on radiographs. The screw was excessively long, piercing the C3 vertebral body and providing inadequate fixation. To avoid posterior fusion, a modified anterior approach was used. An entry point was selected 10 mm lateral to the midline, along the anterior rim of the C2 vertebral body. A large-diameter lag screw was then passed to the tip of the fragment. An angled curette was introduced into the fracture gap through the interval between the odontoid and the C1 ring. Autogenous bone was packed into the gap and along the old screw tract. RESULTS: At the 2-year follow-up the patient had a solid union with no neck pain, no headaches, no radicular symptoms, and excellent range of motion. The approach is described. CONCLUSION: In properly selected patients an anterior revision approach can provide a better outcome than posterior cervical fusion. This modified approach allows placement of an adequate fixation screw in a vertebra damaged by previous screw failure.

Morphometric model of normal rabbit dorsal root ganglia.

The rabbit dorsal root ganglion is an important model of pain mechanisms in the human spine. A morphometric model of the normal rabbit dorsal root ganglion was constructed to provide quantitative comparisons with injured ganglia. Lumbar ganglia were studied under light and electron microscopy using simple stereologic methods. Neuronal diameter ranged from 18 to 85 microns, with 60% between 30 and 50 microns. Neurons constituted approximately 30% of dorsal root ganglion volume, and neuronal nuclei accounted for 14% of neuronal volume and 4% of dorsal root ganglion volume. Contributions from organelles to dorsal root ganglion volume were: mitochondria, 1.5%; rough endoplasmic reticulum, 9.4%; lysosomes, 0.2%; golgi, 0.5%. This morphometric model facilitates quantitative analysis of ganglia exposed to direct or indirect stimuli, providing important information on the structural changes that influence pain production.

Primary tumors of the spine.

Eighty-two cases of primary neoplasms of the spine, diagnosed and treated at the University of Iowa, were reviewed in an attempt to identify features of diagnostic and prognostic importance, and to evaluate the effectiveness of surgical treatment with respect to survival. Thirty-one benign and 51 malignant tumors were identified. The mean follow-up in benign lesions was 9.7 years and 3.8 years in malignant lesions. Plain roentgenograms demonstrated the spinal lesion in 81 of 82 cases (99%). All spinal segments were involved, the cervical spine least frequently. Malignancy proved to be associated with an older age at diagnosis, a higher incidence of neurologic deficit, and a higher incidence of occurrence in the vertebral body. Five-year survival for patients with benign tumors was 86%, with no significant relationship between type of surgery and survival. Five-year survival in malignant lesions did correlate with the extent of initial surgery and with the tumor type. Five-year survival in patients undergoing curettage for malignancy was nil, in those undergoing incomplete resection, 18.7%, and in patients having complete excision, 75%. Plain anteroposterior and lateral roentgenograms should be obtained as a screening study in patients with persistent or atypical back pain or neurologic signs. CT scanning, myelography, and magnetic resonance imaging studies may be utilized to establish the physical margins of the lesion and to evaluate cord impingement. Surgical extirpation should be attempted whenever possible in malignant and benign aggressive lesions. In this series, the prolonged survival seen with complete excision justifies an aggressive surgical approach to the treatment of these tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Responses of mechanosensitive afferents to manipulation of the lumbar facet in the cat.

STUDY DESIGN: The response of mechanosensitive afferent nerve endings in the lumbar spine to manipulation of a lumbar facet isolated using a unique surgical approach was studied in anesthetized adult cats. OBJECTIVES: To characterize sensory nerve endings in the lumbar spine with respect to their receptive field and conduction velocity and to assess their response to facet joint motion. SUMMARY OF BACKGROUND DATA: Previous studies have identified the presence of encapsulated endings in normal human facet capsules and have documented the presence of mechanosensitive units responsive to spinal loading. Previous neurophysiologic studies have used preparations that stripped all paraspinous musculature away from the field to expose the facets and lamina. METHODS: A unique hemilaminectomy approach was developed that permitted physiologic loading of the lumbar facet without disturbing its overlying musculature. Recordings of single unit afferent activity were made from fine filaments teased from the L6 dorsal root. Response to L5-L6 facet motion was studied by applying cranial, craniomedial, and medial distractive forces and lateral compressive forces to the facet joint. RESULTS: Single unit recordings were obtained from 16 afferents with receptive fields in the lumbar spine. Seven of 16 afferents had receptive fields in or near the facet, and the remaining nine afferents had receptive fields in paraspinal tissues some distance from the facet joint. There were nine Group II afferents, three Group IV, and four unclassified afferents. The majority of endings responded in a graded fashion relative to the direction of force applied. CONCLUSIONS: Mechanosensitive endings in the lumbar spine show graded sensitivity to the direction of facet manipulation. These Group III and IV afferents can reside some distance from the facet joint and remain sensitive to facet motion.

Endoscopic approaches to metastatic thoracic disease.

Traditional approaches to thoracic metastases and spinal cord compression have been well worked out and validated in the literature. Anterior decompression is clearly superior to laminectomy; vertebrectomy and reconstruction are indicated for sagittal collapse, instability, and pain; and surgical decompression is necessary in cases of bony impingement. The role of endoscopic and minimally invasive techniques in treatment of metastatic disease is evolving. Dr. Lieberman advocates the use of thoracoscopic anterior approaches as the principal application in these patients, whereas Dr. McLain has found that endoscopic assistance has vastly improved his results with posterolateral decompression. The two authors weigh the relative advantages and disadvantages of these approaches for the selected patient with metastatic thoracic disease.

Effects of whole body vibration on dorsal root ganglion neurons. Changes in neuronal nuclei.

STUDY DESIGN: This blinded, histomorphometric analysis compared neuronal nuclei from lumbar dorsal root ganglia from three groups of rabbits: normal controls, immobilized controls, and an experimental group exposed to daily, whole body vibration. OBJECTIVES: To identify ultrastructural changes in dorsal root ganglion neurons consistent with, and capable of producing, neuropeptide changes previously documented in vibration-exposed animals. METHODS: Normal adult rabbits were exposed to modulated whole body vibration at a frequency and amplitude previously shown to produce changes in dorsal root ganglion neuropeptides. Lumbar ganglia from control and vibrated rabbits were fixed, stained, and studied under transmission electron microscopy. One-thousand-two-hundred cells were sampled, and 190 appropriately sectioned cells were analyzed. SUMMARY OF BACKGROUND DATA: Epidemiologic studies have suggested a strong correlation between vibration and back pain. Previous studies have shown that short-term exposure to whole body vibration alters the normal neuropeptide profile seen in dorsal root ganglion neurons. RESULTS: Nuclear clefting was increased 39% in vibrated nuclei relative to controls, and nuclear pores were increased 46% in areas of clefting compared with adjacent nonclefted segments and controls (P < .001). Mitochondria, rough endoplasmic reticulum, and free ribosomes crowded the cleft spaces of vibrated cells, and the normal perinuclear clear space was lost. Mitochondrial and lysosomal volumes were significantly increased in vibrated cells. CONCLUSIONS: These ultrastructural changes, generated by a physiologically valid vibration stimulus, provide an anatomic link between the clinical observation of increased back pain and the biochemical alterations involving pain-related neuropeptides.