Automatic analysis of the electromyographic interference pattern. Part I: Development of quantitative features

We have developed three new features of the electromyographic interference pattern (IP), based on the turns and amplitude of the signal, to quantitate some of the features of the IP that are usually assessed subjectively by an electromyographer. The activity measures the fullness of the IP. The upper centile amplitude (UCA) defines the upper limit of the maximum peak-to-peak amplitude of the motor unit action potentials (MUAPs) contained in the IP. The number of small segments (NSS) measures the complexity of the IP, which is a reflection of the polyphasicity of the component MUAPs. The activity and the logarithm of the UCA correlate strongly with the force of muscle contraction at which the IP is measured. The NSS initially increases with the force of contraction and becomes relatively constant at higher force levels. The normal values of these features and the interpretation of their relationships are described in companion papers.     

A comparison of quantitative EEG frequency analysis and conventional EEG in patients with focal brain lesions.

The sensitivity and specificity of quantified EEG frequency analysis (EEGFA) were assessed in a group of patients with CT or MRI verified unilateral cerebral lesions and compared with the results of conventional EEG interpretations. Digital EEG recordings were obtained in 25 patients and 25 normal control subjects during performance of an alerting task. Recording artifacts were carefully eliminated. The results of EEGFA were then statistically compared with those of 75 additional normal subjects in the same age range. Complete conventional EEGs were blindly interpreted by two independent electroencephalographers using a structured reporting procedure. We observed similar overall sensitivities for the two methods. Optimal yield for EEGFA was associated with the use of longer edited EEG lengths, longitudinal bipolar montage, and normative data based on total EEG power. In those recordings with normal or mildly abnormal EEG backgrounds the two techniques were to an extent complimentary, each detecting abnormalities missed by the other. In such circumstances EEGFA may be useful as an extension of conventional EEG interpretation.     

Psychogenic tremor disorders identified using tree-based statistical algorithms and quantitative tremor analysis.

Detecting psychogenic tremors (PsychT) is often challenging. As there are no laboratory investigations or imaging techniques that can confirm the diagnosis, PsychT is identified on a clinical basis. We present a tree-based statistical algorithm derived from quantitative computerized tremor recordings as a novel method to help in the recognition of PsychT. The goal of this study was to show that objective data from computerized tremor recordings, when processed through a tree-based statistical algorithm, can be used to determine whether a patient can be classified as having PsychT.     

A quantitative electromyographic index that is independent of the force of contraction

Quantitative EMG has been used to improve the accuracy of the diagnosis of myopathy. Equipment is available commercially that utilizes the Willison method of quantification, but the technique has not been widely used because of the necessity of measuring muscle contraction force. An analysis of the basic parameters of the Willison method of quantification was performed for forces of 10, 20, 40 and 60% of maximum for 16 normal subjects for the deltoid muscle. An index was derived from the basic parameters that is independent of the force of contraction. The index is a standardized value for turns/sec expressed as a logarithm. The index has a mean of 1.171 with a standard error of 0.059 for a sample size of 10 muscle sites. Quantitative EMG can be utilized in routine clinical examinations by applying mild to moderate resisting forces to patients, and the proposed index can be determined graphically. The force applied to patients can be maintained within the range of the forces investigated by estimating the force of contraction, evaluating patient effort and fatigue, and monitoring the parameter of total amplitude per second.     

A quantitative analysis of saccades and smooth pursuit during visual pursuit tracking. A comparison of schizophrenics with normals and substance abusing controls.

The eye movements of schizophrenic patients are characterized by decreased smooth pursuit gain and an increased frequency of saccades. However, the nature of these saccades and their function during smooth pursuit has not been clearly defined. To address this issue we examined the eye movements of 22 schizophrenic patients, 20 substance abusing patients (primarily alcohol; some with concomitant cocaine and/or cannabis abuse), and 17 normal controls during a visual pursuit task using infra-red oculography. A computerized pattern recognition algorithm divided pursuit eye movements into two basic components: smooth pursuit and saccadic eye movements. The algorithm also determined eye position error and velocity error before and after each saccade. Schizophrenic patients had lower smooth pursuit gain (p less than 0.02) and made more saccades during smooth pursuit (p less than 0.02) than either comparison group. When saccades were assigned to subcategories based on direction and position error, only the frequency of 'catch-up' saccades differentiated schizophrenic patients from the comparison groups (p less than 0.05). Smooth pursuit gain was negatively correlated with saccadic frequency among all three subject groups. Eye velocity preceding saccades was significantly lower among the schizophrenic patients, but pre or post saccadic position error did not differ among the three groups. Discrete analysis of the fine structure of visual pursuit tracking may lead to a better understanding of eye movement abnormalities in schizophrenia.     

Conversational discourse analysis procedures: A comparison of two paradigms

Background: Previous research has suggested that individuals with closed head injury (CHI) have difficulty with the communication skills required for a successful conversational exchange. A variety of analysis paradigms have been used with this population and provide evidence to support that conversational discourse deficits do exist in individuals with CHI. However, the use of various analytical procedures renders it difficult for researchers to draw consistent conclusions and hinders the development of evidence-based practice guidelines for conversational discourse evaluation or treatment for individuals with CHI.

Aims: The purpose of this study was to evaluate two conversational discourse analysis procedures. It was hypothesised that modifying a Conversational Appropriateness paradigm used successfully in previous research would provide additional information about conversational ability ultimately leading to more conclusive results.

Methods & Procedures: A series of conversations elicited from one individual with CHI were analysed using two analysis schemes: Conversational Appropriateness (e.g., Blank & Franklin, 1980 Blank, M. and Franklin, E. 1980. Dialogue with preschoolers: A cognitively-based system of assessment. Applied Psycholinguistics, 1: 127–150.  [Google Scholar]; Coelho, Youse, & Le, 2002 Coelho, C. A., Youse, K. M. and Le, K. N. 2002. Conversational discourse in closed-head-injured and non-brain-injured adults. Aphasiology, 16: 659–672. [Taylor & Francis Online] , [Google Scholar]) and a Modified Conversational Appropriateness paradigm designed for this study.

Outcomes & Results: The results supported the hypothesis suggesting the original Conversational Appropriateness paradigm may not be completely representational of conversation ability of individuals with CHI. A Modified Conversational Appropriateness procedure may be more appropriate for the CHI population, as it appears to capture the nuances that are known to affect conversational performance in individuals with CHI revealing greater detail regarding deficits in conversational participation.

Conclusions: Comparing two conversational discourse analysis paradigms provided valuable insight into measures that may more adequately define the conversation ability of individuals with CHI. Modifying a discourse analysis procedure that has been shown to be successful in the past can provide additional detail for therapists to utilise when assessing and designing therapy goals for an individual with CHI. Although further research is needed, if a reliable, valid procedure can be developed for clinical use the possibility of developing evidence-based practice guidelines for discourse assessment and treatment may be more attainable.     

The finger-tapping test. A quantitative analysis

A quantitative analysis of the so-called finger-tapping test was performed on 111 normal subjects. Quantitative analysis was also performed on 17 patients with cerebellar diseases, 14 with parkinsonism, and 14 with hemiparesis. All analyses were performed in a simple fashion using an 8-bit microcomputer fed through an electrocardiographic apparatus. The results in normal subjects were as follows: (1) tapping frequency lowered with advancing age; (2) men tapped faster than women; and (3) tapping with the dominant finger was faster than tapping with the nondominant finger in normal subjects. Tapping frequency can distinguish patients with motor dysfunctions of cerebellar, basal ganglia, and cerebral origins from normal subjects. Only the time-sequential histograms of tapping intervals could distinguish the motor dysfunctions studied.     

A comparison of primidone, propranolol, and placebo in essential tremor, using quantitative analysis.

The effects of placebo, propranolol and primidone were compared in 14 patients with essential tremor in a double blind, randomised, crossover study. Objective measures of tremor were obtained using an accelerometer with subsequent spectral analysis. Both propranolol (p less than 0.01) and primidone (p less than 0.01) gave significant improvement in tremor, but there was no significant difference in improvement between these drugs. Patients with higher dominant frequencies of tremor tended to respond to both drugs, while those with lower frequencies improved on one or other. There was no differential effect between the drugs with the frequency of tremor.     

A comparison of quantitative EEG features for neonatal seizure detection.

OBJECTIVE: This study was undertaken to identify the best performing quantitative EEG features for neonatal seizures detection from a test set of 21. METHODS: Each feature was evaluated on 1-min, artefact-free segments of seizure and non-seizure neonatal EEG recordings. The potential utility of each feature for neonatal seizure detection was determined using receiver operating characteristic analysis and repeated measures t-tests. A performance estimate of the feature set was obtained using a cross-fold validation and combining all features together into a linear discriminant classifier model. RESULTS: Significant differences between seizure and non-seizure segments were found in 19 features for 17 patients. The best performing features for this application were the RMS amplitude, the line length and the number of local maxima and minima. An estimate of the patient independent classifier performance yielded a sensitivity of 81.08% and specificity of 82.23%. CONCLUSIONS: The individual performances of 21 quantitative EEG features in detecting electrographic seizure in the neonate were compared and numerically quantified. Combining all features together into a classifier model led to superior performance than that provided by any individual feature taken alone. SIGNIFICANCE: The results documented in this study may provide a reference for the optimum quantitative EEG features to use in developing and enhancing neonatal seizure detection algorithms.     

A prospective comparison between two seizure classifications.

The International Classification of Epileptic Seizures is the most widely used, but an alternative system based purely on ictal symptoms and signs has been proposed: the semiological classification. Our objective was to compare the two in a sample of patients evaluated at epilepsy centers. We collected 78 consecutive patients evaluated in outpatient epilepsy clinics who subsequently underwent noninvasive video-EEG monitoring at three centers. Patients with pseudoseizures were excluded. Seizures were first classified based on information obtained during clinic visits, and again after video-EEG monitoring. Each time, seizures were classified using both the International Classification and the semiological classification. Eventual epilepsy syndrome diagnosis was based on all the clinical data, video-EEG monitoring, and other independent tests including imaging studies. Sixty-six (87%) patients were classified as having 'complex partial seizures' in the International Classification. Using the semiological classification, these same 66 patients were classified as follows: automotor (34), dialeptic (17), hypermotor (13), hypomotor (2). Seizure classification changed between initial 'clinic-based' data and the 'monitoring-based' classification in 27 cases using the ILAE, vs. six using the semiological classification. Seizure classification tended to change significantly between pre- and post-monitoring using the ILAE but not the semiological classification. The term complex partial seizure included multiple categories of the semiological classification, and was very nonspecific. The semiological classification may be better suited for everyday clinic use, since it is based solely on clinical characteristics.     

A comparison of two methods of diagnosing hysteria.

The authors compare the syndrome of hysteria, defined as or indicated by a specified response to a 55-item symptom checklist previously used by Guze and other researchers, with the definition of hysterical personality in the second edition of APA's Diagnostic and statistical Manual of Mental Disorders (DSM-II). When 20 control subjects and 10 hysterical personalities (DSM-II) were given the Perley-Guze test, the results showed a close correlation between positive scores on the symptom checklist and the DMS-II diagnosis. The authors comment briefly on the theoretical usefulness and practicality of the test and note some difficulties in administration.     

Cost-minimization analysis of two algorithms for diagnosing acute pulmonary embolism

INTRODUCTION: Pulmonary embolism is a common disorder that often requires extensive diagnostic testing. We hypothesized that an algorithmic approach to diagnosis of pulmonary embolism based upon clinical risk stratification and D-dimer testing would be less costly than a standard approach. MATERIALS AND METHODS: We constructed a decision tree based upon two published algorithms for diagnosing acute pulmonary embolism. Branch point probabilities were obtained from the best available published literature. Costs were based upon Medicare charges. From this we obtained a base-case analysis and conducted sensitivity analysis. RESULTS: Our base-case analysis revealed that the cost-per-patient for diagnostic testing were US$216.52 for the algorithm based upon pre-test probability and D-dimer testing and US$538.62 for the standard algorithm. The cost difference per patient evaluated was US$322.10. One- and two-way sensitivity analyses did not reveal any instances in which the clinical risk algorithm was more costly than the standard algorithm. Two-way sensitivity analysis revealed several scenarios in which the standard algorithm would be less costly; however, the conditions required for these scenarios are rarely encountered in clinical practice. CONCLUSIONS: Costs of testing using an algorithm based on clinical pre-test probability and D-dimer testing are less than with a standard approach for evaluating suspected acute pulmonary embolism. This new algorithm has previously been shown to be safe and has the potential for large cost savings if widely applied.     

A comparison of two benzodiazepine hypnotics administered with alcohol

Two benzodiazepine hypnotics were administered alone or in combination with alcohol to normal male volunteers. In the doses given, alcohol potentiated the effects of the benzodiazepines on some but not all performance measures.     

A comparison of interhemispheric transmission times as measured by verbal and manual reaction time.

Interhemispheric transmission times (IHTTs) were calculated for 33 right-handed subjects. Verbal and manual response times (RTs) were recorded to visual stimuli exposed in either the left or right visual fields (LF, RF) for 50 msec. Each subject received 15 stimuli (dots) in the LF (1.5 degrees to the left of fixation), 15 stimuli in the RF, and 15 blank trials in both the verbal and manual response condition. IHTTs were calculated for each subject by subtracting the mean RF RT (I.E., uncrossed path) from the means LF RT (i.e., crossed path). Results indicated a nonsignificant IHTT obtained under the manual response condition of 5 msec and a highly significant IHTT obtained under the verbal response condition of 20 msec. While no significant correlation was found between IHTTs obtained under both response conditions, high correlations were found between component RT measures (i.e., manual RF RT, manual LF RT, verbal RF RT, and verbal LF RT). Thus, IHTT is independent of simple RT.     

Automatic quantitative analysis of the electromyogram in partially denervated distal muscles: comparison with motor unit counting.

Using the ANOPS-101 minicomputer, an automatic analysis of muscle action potentials (MAP) was performed on a total of 53 extensor digitorum brevis (EDB) and abductor pollicis brevis (APB) muscles in patients with other evidence of denervation. The results were compared with observations made on 27 control subjects and they were also matched against estimates of functioning motor units made by the incremental stimulating technique of McComas et al (1971). Although the incidence of abnormal MAP parameters was relatively low in both muscles, it was possible to improve the diagnostic yield by combining the results for individual muscles. The relative merits and disadvantages of motor unit counting and automatic MAP analysis are discussed.     

Creatine kinase level and its relationship with quantitative electromyographic characteristics in amyotrophic lateral sclerosis

Objective

To explore the relationship between serum creatine kinase (CK) level and electromyographic characteristics in patients with amyotrophic lateral sclerosis (ALS).