Surface electrode somatosensory-evoked potentials in spinal surgery: implications for indications and practice

STUDY DESIGN

A retrospective study of 442 major spinal operations with spinal cord monitoring performed in a University Hospital between 1982 and 1992 was performed.

OBJECTIVES

To assess the reliability of the authors' method for monitoring by somatosensory-evoked potential recording, to determine criteria for intraoperative corrective action, and to redefine the need for the wake-up test.

SUMMARY OF BACKGROUND DATA

The routine use of somatosensory-evoked potential monitoring in spinal surgery remains controversial. In Nottingham, the authors have used a method of recording from either scalp or high cervical electrodes.

METHODS

The recordings and outcomes of all monitored spinal operations between the years 1982 and 1992 were reviewed.

RESULTS

In 442 procedures, 23 technical failures (no reliable monitoring) occurred. Most technical failures were in patients with severe preoperative neurology, identifiable by somatosensory-evoked potential recording before operation. In the remaining 419 procedures, a significant intraoperative change in response occurred in 70 procedures (16.7%). Using the definitions of the American EEG Society, the authors identified 10 true-positives and 60 false-positives. There were no false-negatives. A wake-up test was performed if an amplitude drop greater than 50% from baseline value persisted after attempts to correct any possible identifiable intraoperative cause. This occurred in only 21 patients (5%). In the true-positive group, somatosensory-evoked potential recordings remained persistently abnormal despite an apparently normal subsequent wake-up test. The sensitivity of the method according to current definitions was 100% and the specificity 85.33%.

CONCLUSIONS

Modified guidelines are needed for routine intraoperative use of somatosensory-evoked potential monitoring in spinal surgery. Such guidelines should avoid the term "false-positive" as currently defined and concentrate on the causative analysis of abnormal responses that warn of critical spinal cord dysfunction before that becomes irreversible and allow for appropriate action. Information from this monitoring method alerted the surgeon to the possible need for corrective action in an additional 9.78% of the reported patients, who traditionally would have been regarded as false-positives. A wake-up test still is indicated in patients with persistent suppression of their somatosensory-evoked potential despite correction of any identifiable cause and in cases of technical failure. The current method proved flexible, versatile, and reliable for future use.

Immunization levels and risk factors for low immunization coverage among private practices

OBJECTIVES

Previous studies have indicated that provider characteristics are an important determinant of immunization coverage. The objectives of this study were to: 1) assess immunization coverage levels among 2-year-old children receiving care in private practices in 3 California counties; and 2) evaluate practice and patient risk factors for low immunization coverage.

STUDY DESIGN

Cross-sectional chart review of immunization histories and provider survey of immunization policies.

SETTING

Forty-five randomly selected, private medical practices in 3 counties in California.

PATIENTS

Children 12 to 35 months old, followed by the participating practices.

METHODS

Providers underwent a detailed assessment of their immunization coverage and completed a questionnaire describing their immunization policies and procedures. Immunization data were abstracted from randomly selected medical charts of children 12 to 35 months old. Only patients who met the criteria for active status (>/=2 visits and >/=1 visit during the preceding 18 months) were included in analyses. Immunization coverage levels were calculated and logistic regression was used to estimate the risk of underimmunization associated with different practice and child characteristics.

RESULTS

Of the 72 eligible practices that were contacted, 45 participated in the study, yielding a participation rate of 62%. The median immunization coverage of participating offices was 54% (range: 0%-91%). Multivariate analysis revealed 5 independent risk factors for underimmunization. The strongest predictors were having fewer than 50% active children in the practice and children having fewer than 8 visits to the provider. Other significant predictors were the percentage of patients in the practice on Medicaid, administering diphtheria-tetanus-pertussis 4 at a separate visit from the Haemophilus influenzae type b booster, and practice location.

CONCLUSIONS

These data provide new insights into immunization practices in an important clinical setting that has been poorly characterized previously. Immunization coverage levels were found to be low and significant risk factors for underimmunization were identified. Recommendations are made for immunization policy changes and targeting of immunization improvement interventions at practices that may be at risk for low immunization coverage. immunization, vaccination, immunization programs, primary prevention, private practice, child, preschool, pediatrics, family practice.

ICAM-1 expression by vascular smooth muscle cells is phenotype-dependent

Atherosclerosis is an inflammatory disease characterised by increased expression of adhesion molecules for leukocytes on both the surface of dysfunctional endothelium and on smooth muscle cells (SMC) within the lesion. It is also characterised by altered SMC phenotypic expression, indicated by a decreased volume fraction of myofilaments (V(v)myo) [1,2] and changes in gene expression [3]. The present study used an in vitro model to investigate, by immunofluorescence staining and flow cytometry, the influence of phenotype on vascular SMC expression of the adhesion molecule for leukocytes, intracellular adhesion molecule-1 (ICAM-1), and the regulatory mechanisms involved in this process. Smooth muscle cells with a high V(v)myo, freshly isolated from rat aortic media, expressed little or no ICAM-1 and this could not be induced by interleukin-1beta (IL-1beta). As SMC modulated phenotype, indicated by decreasing V(v)myo over the first 5 days of culture, there was a concomitant increase in ICAM-1 expression. At day 9 of primary culture, when SMC cultures had returned to the high V(v)myo phenotype, ICAM-1 expression was markedly lower. However, these cells retained the capacity to express ICAM-1 in response to IL-1beta. After several passages in culture, cells (with a low V(v)myo) constitutively expressed ICAM-1, with levels further up-regulated in response to IL-1beta. These changes in ICAM-1 expression were not related to proliferative state, since similar results were obtained with growth arrested SMC. Investigation of signalling pathways involved in regulating ICAM-1 expression by primary vascular SMC suggested a complex regulatory mechanism. Activation of adenyl cyclase (with forskolin) caused a significant increase in cells expressing ICAM-1. Treatment with inhibitors of protein kinase C (chelerythrine chloride), protein tyrosine kinase (genistein), or the transcription factor NF-kappaB (PDTC) had no significant effect on IL-1-induced ICAM-1 expression. However, in the presence of serum, both genistein and PDTC caused a significant increase in basal expression. The results indicate that ICAM-1 expression by SMC is phenotype-dependent, with expression evident only after cells have modulated to a low V(v)myo phenotype. They also indicate the existence of complex regulatory mechanisms, possibly involving the SMC cytoskeleton.

Metastatic neuroblastoma of the mandible mimicking osteogenic sarcoma radiologically. Case report

This paper presents a case of a neuroblastoma of the adrenal gland metastasizing to the mandible of a 21-month-old infant, which presented radiographically as the so-called 'sun-ray' appearance, characteristic of osteogenic sarcoma.

Resistance of ovine, caprine and bovine endothelial cells to Clostridium perfringens type D epsilon toxin in vitro

Ovine, caprine and bovine endothelial cells were grown in vitro and challenged with Clostridium perfringens type D epsilon toxin to compare their susceptibility to this toxin. Madin Darby canine kidney (MDCK) cells, which are known to be susceptible to epsilon toxin, were used as a positive control. No morphological alterations were observed in any of the endothelial cell cultures tested, even after challenging with doses as high as 1200 MLD50/ml of epsilon toxin. MDCK cells showed contour rounding and nuclear condensation as early as 30 min after exposure to 100 MLD50/ml of epsilon toxin and after 60 min of exposure to 12.5 MLD50/ml of the same toxin. All the MDCK cells were dead after 3 h of exposure to all concentrations of epsilon toxin. The results indicate that ovine, caprine and bovine endothelial cells are not morphologically responsive to the action of epsilon toxin in vitro.

Health consequences of religious and philosophical exemptions from immunization laws: individual and societal risk of measles

CONTEXT

All US states require proof of immunization for school entry. Exemptions are generally offered for medical, religious, or philosophical reasons, but the health consequences of claiming such exemptions are poorly documented.

OBJECTIVES

To quantify the risk of contracting measles among individuals claiming religious and/or philosophical exemptions from immunization (exemptors) compared with vaccinated persons, and to examine the risk that exemptors pose to the nonexempt population.

DESIGN, SETTING, AND PARTICIPANTS

Population-based, retrospective cohort study of data from 1985 through 1992, collected by the Measles Surveillance System of the Centers for Disease Control and Prevention, as well as from annual state immunization program reports on prevalence of exemptors and vaccination coverage. The study group was restricted to individuals aged 5 to 19 years. To empirically determine and quantify community risk, a mathematical model was developed that examines the spread of measles through communities with varying proportions of exemptors and vaccinated children.

MAIN OUTCOME MEASURES

Relative risk of contracting measles for exemptors vs vaccinated individuals based on cohort study data. Community risk of contracting measles derived from a mathematical model.

RESULTS

On average, exemptors were 35 times more likely to contract measles than were vaccinated persons (95% confidence interval, 34-37). Relative risk varied by age and year. Comparing the incidence among exemptors with that among vaccinated children and adolescents during the years 1985-1992 indicated that the 1989-1991 measles resurgence may have occurred 1 year earlier among exemptors. Mapping of exemptors by county in California indicated that exempt populations tended to be clustered in certain geographic regions. Depending on assumptions of the model about the degree of mixing between exemptors and nonexemptors, an increase or decrease in the number of exemptors would affect the incidence of measles in nonexempt populations. If the number of exemptors doubled, the incidence of measles infection in nonexempt individuals would increase by 5.5%, 18.6%, and 30.8%, respectively, for intergroup mixing ratios of 20%, 40%, and 60%.

CONCLUSIONS

These data suggest the need for systematic review of vaccine-preventable incidents to examine the effect of exemptors, increased surveillance of the number of exemptors and cases among them, and research to determine the reasons why individuals claim exemptions.

Coexisting allergies to latex and to muscle relaxants in a primigravida

A 23-year-old primigravida weighing 67 kg required urgent caesarean section for fetal distress. She had been admitted a week earlier at 34 weeks' gestation for bed rest and observation because of worsening pre-eclampsia.

Effect of serial passage in tissue culture on sequence of omp1 from Chlamydia trachomatis clinical isolates

Previous epidemiological studies of Chlamydia trachomatis frequently have required expansion of isolates in tissue culture. The possibility that C. trachomatis omp1 might undergo mutation during such expansion has not been examined systematically. We found no differences in the omp1 sequences from 10 clinical specimens before and after 20 in vitro passages.

Fibrous dysplasia of the jaw bone: a review of 15 new cases and two cases of recurrence in Jamaica together with a case report

The authors reviewed 15 new cases of fibrous dysplasia of the jaw bone and two cases of recurrence seen in Jamaica between 1980 and 1995. Only cases which had a histological confirmation of fibrous dysplasia were included. The clinical behaviour and radiological findings of these cases were studied from the case files, either at the Cornwall Regional Hospital or the Kingston Public Hospital in Jamaica.

Dispersion management for wavelength-division-multiplexed soliton transmission

Residual frequency shifts that are due to two-soliton collisions in stepwise exponentially dispersion-tapered fiber are calculated. Two-step dispersion profiles to minimize the frequency shifts and associated timing jitter are specifically identified. These profiles will improve the performance of wavelength-division-multiplexed soliton systems and permit operation with longer amplifier spans over an increased bandwidth.

Energy-scaling characteristics of solitons in strongly dispersion-managed fibers

We present an empirical scaling law that models the increased energy required for launching a soliton into an optical system with sections of both normal and anomalous dispersion fiber. It is shown that the inclusion of periodic attenuation and amplification can be handled as separate problems, provided that the interval between optical amplifiers is substantially different from the period of the dispersion map. These concepts are illustrated by reference to an example system comprising dispersion-shifted fiber combined with anomalous standard fiber.

Medial epicondylectomy or ulnar-nerve transposition for ulnar neuropathy at the elbow?

We carried out a prospective randomised study comparing medial epicondylectomy with anterior transposition for the treatment of ulnar neuropathy at the elbow. The mean follow-up period was 4.5 years and we assessed the patients neurologically and orthopaedically. Neither procedure appeared to have a significant effect on elbow function. Our study showed better results after medial epicondylectomy; in particular patient satisfaction was higher than after ulnar nerve transposition. There were no significant differences in motor power or nerve-conduction rates and sensory fibres appeared to be more vulnerable to devascularisation.

Modulational instabilities in fibers with periodic dispersion management

We analytically and numerically analyze the occurrence of modulational instability in fibers with periodic changes in the group-velocity dispersion. For small variations, a set of resonances occurs in the gain spectrum. However, large dispersion variations eliminate these resonances and restrict the bandwidth of the fundamental gain spectrum. This research has been motivated by the adoption of dispersion management techniques in long-haul optical communications.

An audit of film reject and repeat rates in a department of dental radiology

A study of film reject and repeat rates was undertaken in the Department of Dental Radiology of King's College School of Medicine and Dentistry over a 6 month period. The aim of the study was to assess the effects of changes implemented after a previous audit, and to carry out a more detailed analysis of the factors influencing the reject and repeat rates using a larger volume of data. The information recorded included the equipment and projection used, and the age of the patient if under 16 years. The overall reject rate was 3.06%, 1.84% less than recorded in the earlier study, and the repeat rate was 0.93%. Positioning errors were the most frequent cause for rejection. Significant differences in reject rates were noted between different projections, and also between qualified staff and those in training. The rejection rate for patients under 16 years was not significantly higher than for patients over 16 years, the most frequent cause of rejection was still positioning faults, but patient movement accounted for a larger proportion of the rejects than was the case in adult patients. The results demonstrate the role of audit in isolating factors leading to additional exposures. The effectiveness of changes implemented following a reject film analysis is also shown.

T lymphocytes affect smooth muscle cell phenotype and proliferation

The effects of rabbit T lymphocytes on rabbit aortic smooth muscle cell (SMC) phenotype and proliferation were investigated in vitro. SMCs seeded at confluent density in primary culture had a volume fraction of myofilaments (Vvmyo) of 49.8 +/- 2.6% after 3 days of culture, not significantly different from that of freshly dispersed cells (Vvmyo, 54.1 +/- 2.1%). Sister cultures of SMCs to which Concanavalin A-activated T lymphocytes or T lymphocyte-conditioned medium was added had significantly lower Vvmyo (35.5 +/- 2.2% and 31.6 +/- 2.3%, respectively) at the same time point. We have previously shown that a decrease in Vvmyo could be induced by the heparan sulfate-degrading activity of living macrophages and by commercial preparations of heparinase. While activated T lymphocytes also completely degraded heparan sulfate-rich 35S-labeled extracellular matrix (an effect inhibited by the addition of 10 micrograms/mL heparin), no heparanase-like activity was detected in T lymphocyte-conditioned medium, indicating that for this cell type SMC phenotypic change is induced by a different mechanism. Incubation of the T lymphocyte-derived cytokine interferon gamma (IFN-gamma) with freshly isolated rat SMCs caused a significant reduction in Vvmyo at day 2 in primary culture from 54.3 +/- 2.1% (control) to 35.4 +/- 3.0%. Furthermore, a neutralizing antibody specific for IFN-gamma removed the effect of T lymphocytes and medium conditioned by them, thus positively identifying IFN-gamma as the T lymphocyte factor responsible for this activity. T lymphocyte-conditioned medium was mitogenic for passaged (low Vvmyo) SMCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Dark soliton sideband formation and stability in periodically amplified systems

We investigate the stability of dark solitons with respect to periodic amplification by studying sideband generation. It is shown that these sidebands grow exponentially as a result of a four-wave mixing process with the cw background. We derive expressions for the positions of the sidebands and present numerical simulations that are in excellent agreement with the theoretical description. A comparison is made with bright solitons, showing that dark soliton propagation is less perturbed only over very short amplifier chains. We also relate our results to laser cavities and discuss the prospects for dark soliton lasers.

Clinical experience with thalidomide in the management of severe oral and genital ulceration in conditions such as Behçet's disease: use of neurophysiological studies to detect thalidomide neuropathy

OBJECTIVE

To examine the efficacy, dose, and safety profile, including neurophysiological testing of thalidomide used in 59 patients (including 23 with Behçet's disease) to treat severe oral or genital ulceration (OGU).

METHODS

We identified prospectively subjects (including women of childbearing potential) who had persistent OGU over periods lasting one to 40 years and whose active ulceration was not controlled by other therapies. They were treated with thalidomide. Retrospectively, we identified the number of subjects with complete resolution of the ulcers at one and two months of thalidomide therapy, and the dose required to maintain that improvement in those individuals who relapsed after stopping thalidomide. The decrease from the baseline sensory nerve action potential (baseline SNAP) amplitude value (derived from median, radial and sural nerve SNAPs) at which the development of paraesthesiae was likely to occur was also determined.

RESULTS

Complete resolution of the ulcers occurred in 81% of patients within one month of thalidomide therapy at doses of 200 mg/day. No further thalidomide was required by 20% of patients responding and in the remainder improvement was maintained with smaller doses (7-200 mg/day). Using an approximate 50% decrease from baseline SNAP as an indication to discontinue thalidomide, the incidence of symptomatic neuropathy was 13.5%. No patients with a decrease of less than 42% developed neuropathy, and a further 13.5% were asymptomatic with a decrease in SNAP between 42 and 69%. Other side effects were seen in 44% of patients. There were no pregnancies and no requirement for urgent pregnancy testing.

CONCLUSIONS

Thalidomide provided a useful therapeutic option in severe oral and genital ulceration which had not responded to other therapies. The physician must remain vigilant to the continuing danger of axonal neuropathy and teratogenesis at all times during thalidomide therapy.

Suppression of soliton interactions by periodic phase modulation

We study analytically and numerically the interaction of adjacent solitons under the influence of a phase modulator. Above a critical value, a bifurcation takes place and the interaction-free lengths are considerably increased.