The effects of bipolar electrode montage on conduction velocity estimation from the surface electromyogram

This study examines the influence of the bipolar electrode montage on conduction velocity (CV) estimation. Electrode montage refers to the combination of two parameters, the inter-electrode distance (IED), the distance between the two electrodes of a bipolar pair, and the inter-signal distance (ISD), the distance between two bipolar signals used to calculate CV. Data from the biceps brachii (BB) and tibialis anterior (TA) of healthy subjects are analysed. Two approaches are used for CV estimation. The first returns a single value per epoch. The second is based on finding velocity values from individual peaks in the signal and results in a peak velocity (PV) distribution being generated per epoch. It is concluded that CV estimation is significantly dependent on the choice of the (IED, ISD) electrode montage. The main results are that the electrode montage affects (1) the mean PV and CV estimates, (typically P < 0.001), (2) the degree of spatial variability, and (3) the width of the PV distributions. The combination of a small IED and large an ISD is recommended.

A case report of a spinal epidural haematoma associated with warfarin therapy

Spinal epidural haematoma is an uncommon, but recognised, clinical entity that needs emergency management. The association of spinal epidural haematomata with warfarin therapy has been described and, in 1956, Alderman stated that this diagnosis should be entertained in any patient receiving anticoagulants presenting with low back pain or sciatic pain. The purpose of this case report is to increase the awareness of this entity among medical personnel and to stress the urgency of management.

Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis

Rectification of the electromyographic (EMG) signal is a commonly used pre-processing procedure that allows detection of significant coherence between EMG and measured cortical signals. However, despite its accepted and wide-spread use, no detailed analysis has been presented to offer insight into the precise function of rectification. We begin this paper with arguments based on single motor unit action potential (AP) trains to demonstrate that rectification effectively enhances the firing rate information of the signal. Enhancement is achieved by shifting the peak of the AP spectrum toward the lower firing rate frequencies, whilst maintaining the firing rate spectra. A similar result is obtained using the analytic envelope of the signal extracted using the Hilbert transform. This argument is extended to simulated EMG signals generated using a published EMG model. Detection of firing rate frequencies is obtained using phase randomised surrogate data, where the original EMG power spectrum exceeds the averaged rectified surrogate spectra at integer multiples of firing rate frequencies. Model simulations demonstrate that this technique accurately determines grouped firing rate frequencies. Extraction of grouped firing rate frequencies prior to coherency analyses may further aid interpretation of significant cortico-muscular coherence findings.

Electromyogram median frequency, spectral compression and muscle fibre conduction velocity during sustained sub-maximal contraction of the brachioradialis muscle

Changes in the median frequency of the power spectrum of the surface electromyogram (EMG) are commonly used to detect muscle fatigue. Previous research has indicated that changes in the median frequency are related to decreases in muscle fibre conduction velocity (MFCV) during sustained fatiguing contractions. However, in experimental studies the median frequency has been consistently observed to decrease by a relatively greater amount than MFCV. In this paper, a new estimate of EMG frequency compression, the Spectral Compression Estimate (SCE), is compared with the median frequency of the EMG power spectrum, the median frequency of the EMG amplitude spectrum and MFCV measured during sustained, isometric, fatiguing contractions of the brachioradialis muscle at 30, 50 and 80% maximum voluntary contraction (MVC). The SCE is found to provide a better estimate of the observed changes in MFCV than the median frequency of either the EMG power spectrum or EMG amplitude spectrum.

A pictorial review of atlanto-axial rotatory fixation: key points for the radiologist

Atlanto-axial rotatory fixation (AARF) is a rare condition which occurs more commonly in children than in adults. The terminology can be confusing and the condition is also known as 'atlanto-axial rotatory subluxation' and 'atlanto-axial rotary dislocation'. Rotatory fixation is the preferred term, however, as in most cases the fixation occurs within the normal range of rotation of the joint. By definition, therefore, the joint is neither subluxed nor dislocated. AARF is a cause of acquired torticollis. Diagnosis can be difficult and is often delayed. The radiologist plays a key role in confirming the diagnosis. The classification system proposed by Fielding in 1977 is most frequently used and will be discussed in detail. Given that this classification system was devised in the days before computed tomography (CT), as well as the fact that combined atlanto-axial and atlanto-occipital rotatory subluxation (AORF) is omitted from the classification, we propose a modification to the classification of this rare but significant disorder. The radiological findings in six cases of AARF will be illustrated, including a case with associated atlanto-occipital subluxation. The pertinent literature is reviewed and a more comprehensive classification system proposed. The imaging approach to diagnosis and the orthopaedic approach to management will be discussed.

Dynamic T1-weighted ferumoxides enhanced MRI for imaging liver hemangiomas: preliminary observations

The T1-based signal-enhancing effects of ferumoxides was studied in five liver hemangiomas on short echo-time gradient-recalled echo dynamic magnetic resonance imaging to assess the utility of this technique to image perfusion patterns in liver hemangiomas. We observed peripheral nodular enhancement with centripetal fill in all hemangiomas. Our results suggest that this imaging technique, after rapid injection of ferumoxides, can be used for lesion characterization.

MR imaging of renal masses interpreted on CT to be suspicious

OBJECTIVE

Prior studies have shown that renal MR contrast enhancement improves the efficacy of mass and proximal vascular evaluation. This study assessed the usefulness of different sequences for characterization of masses that appeared suspicious on CT and for prediction of their potential for malignancy.

SUBJECTS AND METHODS

In a prospective manner 32 patients (age range, 26-78 years: average age, 54 years), each with at least one suspicious mass on CT, were examined with MR imaging. The following sequences were performed: conventional spin-echo with and without fat saturation, fast spin-echo, and dynamic gadopentetate dimeglumine-enhanced infusion using a 1.5-T superconducting magnet. Results were analyzed and compared with pathologic results after resection.

RESULTS

A total of 65 renal masses of average size 2.6 cm (range, 1-10 cm) were detected with dynamic MR imaging. Seventeen of the 65 masses were malignant. Of the 17 malignant masses, three did not enhance on dynamic MR imaging (because of hemorrhage). Sixteen of the 17 malignant masses were heterogeneous on T2-weighted images. Three enhancing masses contained fat and all were angiomyolipomas. Thirty-five of the 65 masses (four with hemorrhage) did not show enhancement, all of which were homogeneous on T2-weighted images and were proven to be cysts. Five masses resulted from infections and had heterogeneous T2 appearance. The remaining masses were three hematomas with hemorrhage, one column of Bertin, and one aneurysm.

CONCLUSION

Renal masses that are interpreted as suspicious on CT may lack MR enhancement because of hemorrhage effects; heterogeneity of their T2 appearance is thus critical in differentiating malignancy from benign disease. Odds-ratio calculations give an adjusted estimate of a 3.36-fold increase (95% confidence interval, 1.8-6.27) in the likelihood of malignancy when masses are heterogeneous on T2-weighted images and a 29-fold increase (95% confidence interval, 3.67-241.8) for predicting malignancy when enhancement is present.

The role of physician recommendation in women's mammography use: is it a 2-stage process?

OBJECTIVE

To explore the use of a 2-stage model in explaining the role of physician recommendation in women's use of mammography screening and to provide an integrated framework for understanding the mammography-use process.

METHODS

Data on 1,301 women aged > or =52 years from the North Carolina Breast Cancer Screening Program (NC-BCSP) questionnaire were combined with information from 91 of their physicians from the North Carolina Medical Board. A 2-stage system of equations using women's characteristics (demographic, health, access), physicians' characteristics (demographic, practice), women's beliefs, and women's report of a physician recommendation was created and statistically tested. The model was estimated using 2-stage logistic and probit estimation.

RESULTS

The 2-stage approach produced different results compared with the single pooled model. In the second-stage mammography-use model, younger age, family history of breast cancer, and a woman's having ever requested a mammogram retained significance (P < or = 0.05) in addition to the predicted value of physician recommendation obtained from the first stage. Women's characteristics significantly associated with physician recommendation in the first stage included some access, health risk, and demographic variables as well as physician age and race (P < or = 0.05).

CONCLUSIONS

A 2-stage model for estimating mammography use among women with regular physicians may be more informative than a single model. These results imply that programs designed to increase mammography rates should focus on ensuring appropriate physician recommendations in addition to encouraging women to request screening. Future research should consider using an integrated framework for evaluating utilization of mammography and other preventive services.

Physicians' recommendations for colon cancer screening in women. Too much of a good thing?

BACKGROUND

Expert groups support periodic colorectal cancer (CRC) screening for persons aged 50 and older but not for persons younger than 50. We were interested in community primary care physicians' recommendations to women for fecal occult blood tests (FOBT), flexible sigmoidoscopy (SIG), and colonoscopy (COL).

METHODS

In a mailed survey of 1,292 community primary care physicians in North Carolina, we queried physicians regarding their recommendations to women for CRC screening.

RESULTS

Analysis was performed on 508 respondents (39%). Recommendation for FOBT (96%) and SIG (69%) for women > 50 years old was high among all subgroups of physicians. Recommendation for women < 50 years old was high for FOBT (82%) but lower for SIG (28%). Overall, 19% of physicians recommended COL. Recommendation for FOBT, SIG, and COL varied by physician specialty, physician age, perceived patient demand, physician need for additional CRC screening information, practice size, and location.

CONCLUSIONS

Although increasing physician recommendation for CRC screening is important, primary care physicians report recommending earlier and more aggressive screening than that supported by national guidelines.

A review of the effects of moderate alcohol intake on psychiatric and sleep disorders

In this chapter we discuss the effects of moderate ethanol consumption on the treatment of psychiatric and sleep disorders. A review of the literature on the interactions of ethanol with neurotransmitters and psychotropic medications suggests that although ethanol affects the clinical course of psychiatric and sleep disorders by different mechanisms, it does so principally through perturbations it causes in the balance of central nervous system neurotransmitter systems, which may modify the clinical course of primary psychiatric and sleep disorders and undermine the therapeutic response to psychotropic medications. Neurotransmitter responses may also be manifested clinically by rebound phenomena, akin to a subsyndromal withdrawal, which affect sleep and precipitate anxiety and mood symptoms. In addition, ethanol also modifies the clearance and disposition of a variety of psychotropic metabolites and interferes with their clinical effectiveness. We recommend that most psychiatric patients, and all patients with sleep disorders, should abstain from even moderate ethanol use, as this may adversely affect their clinical course and response to treatment.

An unusual exposure to methyl bromide leading to fatality

INTRODUCTION

Methyl bromide has been responsible for deaths that usually occur from its accidental inhalation during fumigation.

CASE REPORT

We report an accidental fatality that occurred after methyl bromide seeped through underground conduits from a fumigated building to an adjacent guest house on the same property. The patient developed refractory seizures, intermittent fever, and multiorgan system failure before dying 19 days after exposure. The initial serum bromide was 27 mg/dL. Postmortem analysis detected methyl bromide concentrations of 2.9 mg/dL in the blood, 1.7 mg/dL in the bile, 24 micrograms/g in the liver, and 28 micrograms/g in the adipose tissue.

CONCLUSION

Methyl bromide, although applied under acceptable safety standards, led to the inadvertent death of a young woman. Extreme care must be used when fumigating to insure no unsuspected seepage routes exist.

Electrospray ionization and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of permethylated oligosaccharides

Mass spectra of fragments of permethylated oligosaccharides are analyzed by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Sustained off-resonance irradiation (SORI) collision-induced dissociation (CID), quadrupolar axialization, multiple stages of isolation and dissociation (MSn), and ion remeasurement are exploited for carbohydrate structural analyses. That SORI CID internal energies are adequate for linkage analysis of a permethylated glucose oligomer is demonstrated by identifying ring-opened fragment ions from MALDI-generated mass-isolated and collisionally activated ions. Ion remeasurement and axialization techniques enhance the sensitivity of ion fragmentation analysis. Multiple stages of isolation and dissociation of ion fragments (MSn) provide for structural analysis of an electrospray-ionized permethylated lacto-N-fucopentaose isomer (LNFP II). Compared to MS2 spectra taken with a triple quadrupole, FT-ICR MSn (n > 2) provides more extensive characterization of the parent molecular structure than is available from a single stage of ion isolation and dissociation (MS2).

Acute 3,4-methylenedioxymethamphetamine(MDMA) administration produces a rapid and sustained suppression of immune function in the rat

(+)-3,4-Methylenedioxymethamphetamine (MDMA;'Ecstasy') is a ring substituted phenylisopropylamine that is structurally related to both amphetamines and hallucinogens. The unique behavioural activating properties of MDMA have led to its widespread abuse. MDMA induces many neurochemical, behavioural and endocrine alterations which closely resemble those elicited by exposure to acute stress, suggesting that MDMA could be regarded as a 'chemical stressor'. In addition to the neurochemical, behavioural and endocrine effects of stressor exposure, it has been reported that stress produces alterations in immune function. However, to date the effects of MDMA on immune function have been restricted to in vitro investigations. In this study we report, for the first time, that acute in vivo administration of MDMA (20 mg/kg, i.p.) produced a rapid (within 30 min) suppression of Con A-induced lymphocyte proliferation and a profound reduction in the total leucocyte count in rats that persisted for at least 6 h following injection. These alterations in immune function were accompanied by a significant increase in plasma corticosterone concentrations 30 min post MDMA administration which had returned to baseline values within 6 h of drug administration. In addition, there was a significant depletion in cortical 5-HT concentrations both 30 min and 6 h after MDMA administration. The results of this study provide evidence that in addition to the well established toxic effects of MDMA on the central serotonergic system, a single administration of this widely abused drug induces a rapid and sustained suppression of immune function.

Clinical evaluation of pesticide exposure and poisonings

Pesticide exposures cause disorders varying from straightforward topical irritant reactions, such as those to synthetic pyrethroid insecticides, to complex systemic illness, such as that resulting from cholinesterase inhibition by organophosphate pesticides. The acute illness syndromes associated with pesticides most commonly encountered by clinicians are illustrated here by cases reported to the California Pesticide Illness Surveillance Program. The issues raised include asthma associated with exposure to contaminants in organophosphate insecticides, systemic toxicity of ingested pyrethroids (in children), and illnesses associated with spills or misuse of fumigants.

Central giant cell granulomas of the jaws: phenotype and proliferation-associated markers

Central giant cell granulomas (CGCGs) are jaw tumors of unknown origin that often exhibit an aggressive, though unpredictable, clinical course. The purpose of this study was to determine the immunoprofile of the mononuclear cells that seem to be responsible for the biologic behavior of these tumors. Numbers of cells in cell cycle were also determined and compared in clinically aggressive and non-aggressive CGCGs. Sixteen aggressive and 12 non-aggressive CGCGs were immunohistochemically stained with antibodies to CD34, CD68, factor XIIIa, alpha-smooth muscle actin, prolyl 4-hydroxylase, Ki-67, and p53 protein. Cell populations and numbers of cells in cell cycle were determined through microscopic quantitative assessment. CD34-positive cells were limited to support vessels. CD68-positive mononuclear cells constituted a small population of cells in all tumors. With two exceptions, factor XIIIa-positive cells were rarely seen. Alpha-smooth muscle actin staining was present in approximately half the tumors, and occasionally large numbers of positive cells were seen. Most mononuclear cells were positive for fibroblast-associated antigen. No phenotypic differences were detected between aggressive and non-aggressive tumors. P53 protein did not appear to be overexpressed in CGCGs. Ki-67 staining showed that only mononuclear cells were in cell cycle, and that there were no differences between aggressive and non-aggressive tumors. We conclude that CGCGs are primarily fibroblastic (and myofibroblastic) tumors in which macrophages appear to play a secondary role. Tumor cells show no differentiation toward endothelial cells or macrophage-related dendrocytes (factor XIIIa). Cellular phenotypes and numbers of cells in cell cycle are similar in both aggressive and non-aggressive tumors.

Streamlining the perioperative process

Health-care reform and capitated reimbursements have and will continue to influence decreased lengths of hospital stay and continued efficiency in perioperative nursing practice. Collaborative efforts by perioperative nurses, anesthesia care providers, and surgical staff should continue to emphasize concise documentation processes as well as comprehensive assessment and evaluation phases to prepare patients and families for earlier discharge and recovery at home. The objective of new documentation practices and streamlining perioperative preparation processes is to eliminate the duplication of information, meet standards set by professional organizations, and provide quality, efficient care along with patient and family satisfaction.

MR urography

Developments of MR imaging of static fluid has led to the emergence of MR urography (MRU) as a potential imaging technique of the urinary system. MRU has been shown to be highly sensitive in the diagnosis of urinary obstruction, defining the severity of dilatation, the site, and in the majority of cases, the cause of obstruction. At the current level of resolution, however, MR cannot consistently demonstrate nonobstructive or small obstructing calculi. Demonstration of perinephric and periuretic edema in obstruction helps in the differentiation of acute from nonacute urinary obstruction. MRU has shown potential in the work-up of urinary disease for which intravenous urography used to be performed, without the hazards of intravenous contrast administration.

MR imaging of tibial plateau fractures

Magnetic resonance (MR) images of five patients with acute tibial plateau fractures are presented and correlated with both clinical examination and findings at surgical intervention. The role of MR imaging in the evaluation of both osseous and soft tissue deformity in acute trauma, specifically in patients with tibial plateau fractures is discussed. The value of MR imaging as an alternative to computed tomography and arthroscopic evaluation of these patients is emphasized.

Chlorothalonil, a possible cause of erythema dyschromicum perstans (ashy dermatitis)

We studied 39 patients with erythema-dyschromicum-perstans-like dermatitis seen at Changuinola Hospital in Panama. They were compared with 41 controls. The 2 groups were native field workers of the banana plantations exposed to many pesticides. In 34 patients, there was a positive patch test reaction to 2,4,5,6-1,3-tetrachloroisophthalonilnitrile (chlorothalonil, TCPN) 0.001% in acetone. In 39 cases, biopsies showed a lichenoid tissue reaction compatible with a chronic pigmented dermatitis or erythema-dyschromicum-perstans-like dermatitis. Chlorothalonil is possibly the cause of the pigmented dermatitis observed in the 39 banana farm workers studied. Until additional studies are carried out, we consider this a possible rather than definite cause-and-effect relationship.

A review of the effects of moderate alcohol intake on the treatment of anxiety and mood disorders

BACKGROUND

There is no published review to help the clinician clarify the potential role of moderate ethanol consumption in patients being treated for anxiety and mood disorders. Product labels and textbook chapters routinely warn the individual against the consumption of ethanol when using prescription psychotropic drugs. A general understanding is that the reason for this recommendation is the potential for adverse synergistic effects or sedation and decreased psychomotor performance. What is overlooked by this emphasis on safety is the effect of alcohol use both on the underlying psychiatric disorder being treated and on the effectiveness of drug therapy.

METHOD

We review the available literature on the interactions of ethanol with neurotransmitters and psychotropic medications and explore the clinical consequences of these interactions.

RESULTS

Ethanol might affect anxiety and mood disorders by different mechanisms. Principal among these are the effects of ethanol on multiple neurotransmitter systems, which adapt in different ways to the acute and/or chronic presence of ethanol. Perturbations in the balance of CNS neurotransmitter systems may modify the acute clinical course of primary mood disorders and undermine the therapeutic response to psychotropic medications. Ethanol also modifies the clearance and disposition of psychotropic metabolites and interferes with their clinical effectiveness. Neurotransmitter responses may additionally be manifested clinically by rebound phenomena, akin to a subsyndromal withdrawal, which affect sleep and precipitate anxiety and mood symptoms. Recent alcohol use also may alter the subjective interpretation of the patient's "internal milieu," causing confusion and eliciting reactive psychopathology.

CONCLUSION

While much research remains to be done, there is abundant evidence that patients with mood and anxiety disorders should abstain from even moderate ethanol use, as this adversely affects their clinical course and response to treatment.

Asymptomatic sacroiliitis in inflammatory bowel disease. Assessment by computed tomography

Plain film radiographs and computed tomography scans of sacroiliac joints in 65 asymptomatic patients with known inflammatory bowel disease were performed and evaluated by two radiologists. Computed tomography revealed the presence of asymptomatic sacroiliitis in 21 (32%) of the 65 patients (New York grades 2 to 4); asymptomatic sacroiliitis was identified by plain film radiography in only 10 (18%) of 57 patients (p < 0.001). No correlation was observed between the presence or absence of sacroiliitis, and the age and sex of patients, disease type, or duration of disease. The prevalence and diagnostic value of computed tomography in the detection of asymptomatic sacroiliitis in patients with inflammatory bowel disease are discussed.