Biomedical subjects

J F Jabre

Publications and source records attributed to J F Jabre.

5 recordsLinked to original sources

PubMed1992

The spectrum of concentric macro EMG correlations. Part I. Normal subjects.

Using a concentric macro electrode, both the concentric and macro action potentials of a motor unit were analyzed for duration, area, and amplitude. Eighty-six different motor units were analyzed from the tibialis anterior muscle in 10 normal subjects. The aim of this work was to compare concentric and macro action potential measurements of the same motor unit. The study revealed significant correlations between concentric and macro samples, with the concentric potential's area correlating better with the macro potential than its amplitude. This shows that the 10 to 15 muscle fibers studied by the concentric electrode serve as a good sample of the motor unit as a whole. We briefly review the technique used in concentric macro EMG, as well as describe the methods used for collecting and comparing both concentric and macro action potentials.

Action Potentials↗

PubMed1992

The spectrum of concentric macro EMG correlations. Part II. Patients with diseases of muscle and nerve.

In the second part of this study we investigate the correlations between the concentric and conmac action potentials in motor units of individuals with diseases of muscle and nerve. We studied 86 myopathic and 86 neurogenic motor units and compared their concentric and conmac action potentials. In the patients with myopathy, we found that the concentric motor unit action potential's (MUAP) area correlates strongly with the conmac potential, even better than in normals, while its amplitude correlates less. In the neurogenic group, we found that both the concentric MUAP's area and amplitude correlated very well with their conmac counterpart, more so than in normals. Thus, in pathology, as in normals, measuring the concentric MUAP's area in addition to its amplitude adds to the diagnostic sensitivity of motor unit potential measurements. These findings are discussed in light of the known dynamic and architectural motor unit changes which take place in the myopathic and neurogenic motor unit.

Action Potentials↗

PubMed1992

An investigation of a workplace cluster of Bell's palsy.

We undertook a study to confirm the existence of an apparent cluster of Bell's palsy in an industrial plant ("W4"), and to test etiologic hypotheses regarding chemical exposures, immune suppression, and infectious etiologies. Cases were enumerated by questionnaire. Employees with a history of Bell's palsy ("cases") were invited to participate in a study that included medical history, T cell studies, viral and Lyme disease serologies, and blink reflex studies. Thirty-three unaffected volunteers from W4 and 32 from a comparison building were also tested. Extensive environmental studies were carried out in W4, evaluating infectious, chemical, and radiation exposures. The lifetime incidence of self-reported Bell's palsy was 11.6/10,000 person-years (P-Y) in W4 and 2.4 cases/10,000 P-Y in the comparison building (RR = 4.8, P < .05); the comparison rate was similar to that reported in previous population studies. When restricted to cases occurring after the onset of work, the W4 incidence was 29.2 cases/10,000 P-Y, compared to 4.8 cases/10,000 P-Y in the comparison building (RR = 6.1, P < .05). The cases and noncases did not differ with respect to clinical histories or infectious disease titers. The W4 noncases had small but significant decreases in T lymphocyte (1974 +/- 86 vs 2291 +/- 103) and CD4 (1083 +/- 318 vs 1459 +/- 494) counts compared to the remote noncases. The cases had significantly prolonged RR1, LR1, and LFC values compared to both groups of noncases. No medical or environmental factors were identified that could explain an excess of disease.

Age Factors↗

PubMed1991

Concentric macro electromyography.

Concentric EMG electrodes can record from a few (10 to 15) muscle fibers of a motor unit (MU). Macro EMG, is able to record from the majority of muscle fibers in the MU. The macro EMG electrode uses a single fiber action potential (SFAP) on one channel to trigger the time locked cannula (macro) response on the other channel. To study the concentric motor unit action potential (MUAP), alongside the macro potential, we built a needle electrode combining concentric and macro recording surfaces. The study of 240 motor units in 10 healthy subjects with the single fiber (SF macro) and concentric macro (conmac) electrodes revealed no significant differences between macro potentials areas and amplitudes obtained with either electrode. The ability to study a small and a large section of the motor unit simultaneously offers insights into the local or global nature of motor unit changes not otherwise available to the electromyographer. It also reveals which concentric parameters correlate best with the macro potential and, can even be of great help with the newer EMG signal decomposition techniques; by identifying each motor unit by its concentric and macro waveform simultaneously, it will allow for the "marking" of these motor units helping to reduce the risk of their misclassification when the concentric MUAP is used alone.

Action Potentials↗

PubMed1989

Stimulation SFEMG in myasthenia gravis.

The diagnostic usefulness of single-fiber electromyography (SFEMG) in the diagnosis of neuromuscular transmission disorders is well established. Increased jitter is one of the earliest indications of abnormality. In patients with severe weakness, tremor, or altered consciousness, performance of the study is difficult because of the degree of cooperation needed. We studied five patients and eight normal subjects with voluntary and stimulation SFEMG techniques. Our results, in search of normal values and changes with pathology, revealed differences in the values of jitter and the percentage of abnormal fibers between both techniques. The mean consecutive difference (MCD) is smaller (on average 30% less), and the percentage of abnormal fibers is lower (on average 10% less) with the stimulation technique. These differences are largely explained by the jitter measurement of one endplate with the stimulation technique versus two endplates with the voluntary. They may also be related, however, to the difference in motor unit populations sampled with each technique.

Aged↗